Structural biochemistry (E. A

A biochemical blood test is a laboratory test that can help identify problems with the functioning of internal organs. So, if it is necessary to assess the health of the liver, kidneys or lifespan, a test is carried out to determine the level of the enzyme gamma glutamyltransferase. This specific substance is also found in other internal organs, but an increase in its level rarely occurs due to their dysfunction. Most often, deviations from the norm are caused by problems with the functioning of the liver and gallbladder.

What is gamma HT in a blood test, what are its functions, and when is it necessary? clinical trial to identify the level of its content in the human body? Everyone should know this.

What is GGT and what functions does it perform?

First of all, let's figure out what GGTP is in a biochemical blood test.

On a note. Gamma glutamyl transpeptidase and GGT - gamma glutamyl transferase are identical concepts to each other, therefore the use of the first or second term is equally correct.

Gamma glutamyltransferase is an enzyme that has a protein structure and takes an active part in amino acid metabolism. It accelerates the process of transfer and exchange of amino acid compounds in the body's cells, and after their destruction enters the blood. Since throughout the entire period of functioning of the body there is a regular renewal of its cells, a person’s blood always contains a certain amount of this protein.

However, when a malfunction of internal organs occurs, the process of cellular decay is disrupted, resulting in a sharp increase (sometimes decrease) in the level of gammaglutamine transferase in the blood plasma. Only a clinical blood test for liver enzymes, especially GGT, can reveal deviations from the norm.

Why are these proteins being studied? This is explained by the fact that they react more acutely to damage to liver cells, for example, with hepatitis. For this reason, testing for the GGT enzyme in a biochemical blood test is quite often prescribed by narcologists to patients suffering from alcohol addiction.

When alcohol enters the body, more intense destruction of liver cells occurs, therefore, much more GGTP protein is released into the blood. If at least 30 days have passed since the last use of alcohol, the level of this substance will decrease by 2 times.

GGT in blood biochemistry

Based on all of the above, it is not difficult to understand what GGT is in a biochemical blood test. This is an indicator of amino acid metabolism in the body. The level of this protein indicates the activity of the blood serum, which increases sharply with the destruction of healthy body cells.

If we talk in simple language What is it? GGTP is an enzyme in the blood plasma, the level of which indicates whether there is a malfunction of the liver or other internal organs, and how serious it is.

An analysis to measure the level of this protein is carried out only when indicated.

Indications for blood tests

A blood test for GGTP is mandatory for patients complaining of:

• frequent attacks of nausea;
• profuse vomiting;
• decreased or complete loss of appetite;
• feeling of pressure and pain in the right hypochondrium.

A gastroenterologist or nephrologist (if there are kidney problems) must send the patient for a blood test for gamma HT levels if there is a suspicion of the development of:

• cholecystitis;
• cholelithiasis ( cholelithiasis);
• cholestasis;
• cholangitis;
• hepatitis C.

In these cases, it is not enough to pay attention to the presence of alarming symptoms, since clinical manifestations The above pathologies are very similar to each other. Only a clinical study such as a blood test for glutamyl transpeptidase will help determine exactly what disease is tormenting the patient.

Carrying out this analysis is also important to determine the reasons why the patient has a process of bile stagnation. This helps to prescribe the correct treatment and prevent consequences dangerous to the patient’s health.

Testing for gamma glutamyl transpeptidase is mandatory for persons suffering from chronic alcoholism. Under these conditions, it is important to accurately determine the patient's degree of dependence on ethanol, as well as to understand how severely the liver is affected. Sometimes this helps not only to preserve a person’s health, but also to save his life.

A blood test for GGTP is also indicated for:

• development of allergies to medications, which is accompanied by general intoxication of the body;
• preventive or control assessment of liver health;
• the need to assess liver or kidney function after surgery.

But this is not all the indications for referring a patient to this study. Biochemistry of GGT is performed in the following cases:

• blockages bile ducts;
• the presence of suspicious formations in the pancreas;
• problems with kidney function.

On a note. Donating blood for analysis requires preliminary preparation, therefore, the patient must be instructed by the attending physician what and how to do correctly to obtain reliable data from a biochemical study.

The reasons for an increase in GGT, or gamma glutamyltransferase, can be not only problems with the liver, kidneys, gallbladder or pancreas, but also with the heart. Heart failure or previous myocardial infarction are the main indications for this study.

Norms of gamma glutamyl transferase

The GGT rate varies depending on the age and gender of the patient. Thus, the indicators in men and women do not differ very much, which cannot be said about the normal level of GGTP in older children and newborn infants.

The normal level of ggt in a biochemical blood test in adults is considered to be values ​​ranging from 6-70 units per 1 liter of blood. In this case, it is necessary to take into account the fact that in women the norm of this enzyme is much lower than in men.

In children, the level of gamma glutamyl transferase in the blood is different. So in newborns it can correspond to indicators of 185 units per 1 liter of blood, in six-month-old infants - about 200 U/l. If such high numbers were recorded on the form with the results of blood tests for a newborn, do not worry - in infants, the liver cannot yet produce this enzyme on its own, so the placenta performs this function instead.

Interesting fact. In a blood test for gamma glutamyltransferase in dark-skinned people, the concentration of this enzyme is significantly higher than that in a white-skinned person. Therefore, we can say that the level of this protein also depends on the race of the patient.

Normal for women

The level of GGT in the blood of women is directly dependent on age. The table below will help you understand which indicators in the analysis results should not cause you concern.

The GGTP rate in women may vary depending on:

• equipment used;
• units of measurement (U/l, U/ml, etc.);
• the patient's race.

As for the level of gamma HT in expectant mothers, it depends on the duration of pregnancy:

1. In the first trimester, GGTP ranges from 0-17 units.
2. The second trimester is accompanied by an increase in the level of this substance to 33 units.
3. In the third trimester, the amount of gamma HT in the blood plasma decreases by 1 unit and amounts to 32 units per 1 liter.

Sometimes the level of this protein in the blood of pregnant women can increase sharply, but if this is a temporary phenomenon, you should not be afraid of it. Similar jumps in GGT can occur due to the use of expectant mother vitamin complexes and a large number of foods fortified with vitamins.

Normal for men

The norm of GGTP in the blood of men, as already noted, differs from that of women. big side. Acceptable indicators are shown in this table.

The normal GGT level in men is higher than in women due to the high concentration of enzymes in the prostate gland. But if there is a significant jump in the level of this substance in the patient’s blood, he should be immediately examined for possible abnormalities in the functioning of internal organs.

Reasons for deviation of ggt from the norm

The ggt blood test requires the collection of a sample of material from a peripheral vein. The research process can take from several hours to several days. The results obtained are recorded on a special printed form, after which they are interpreted by the attending physician.

Great value It has correct decoding GGT analysis, which depends on how accurately the patient’s preparation rules for the blood sampling process were followed. Deviations from the prescribed standards may result from:

• long-term intake of vitamin complexes containing a large number of ascorbic acid;
• use of paracetamol or aspirin;
• abuse of oral hormonal contraceptives;
• taking antidepressants, antibiotics, histamine blockers.

A deviation from the norm in the content of gamma glutamate transferase in the body to a greater extent may indicate:

• hepatitis;
• pancreatitis;
• infectious mononucleosis, which caused complications on the liver;
• autoimmune pathologies;
• diabetes mellitus;
• oncological process occurring in the prostate gland or mammary glands;
• rheumatoid arthritis, etc.

If the level of GGTP in the blood is low, this may be a consequence of:

• hypothyroidism;
• treatment of chronic alcoholism with certain types medications;
• taking statins (medicines that lower blood cholesterol levels).

The interpretation of a blood test for GGT should be carried out exclusively by the attending physician. Even if the patient understands what the norm should be and what indicators are a deviation from it, he cannot independently prescribe treatment for himself. Often, after obtaining the data from a biochemical study, the patient is subjected to a number of additional instrumental and laboratory tests that help make an accurate diagnosis.

Most pathologies discovered or confirmed during a blood test for gamma HT require immediate hospitalization of the patient in a hospital and round-the-clock medical supervision, which the patient himself cannot provide for himself at home.

– one of the most popular research methods for patients and doctors. If you clearly know what a biochemical analysis from a vein shows, you can identify a number of serious ailments in the early stages, including - viral hepatitis , . Early detection of such pathologies makes it possible to apply correct treatment and heal them.

The nurse collects blood for testing within a few minutes. Every patient should understand that this procedure does not cause any discomfort. The answer to the question of where blood is taken for analysis is clear: from a vein.

Speaking about what a biochemical blood test is and what is included in it, it should be taken into account that the results obtained are actually a kind of reflection general condition body. However, when trying to independently understand whether the analysis is normal or whether there are certain deviations from the normal value, it is important to understand what LDL is, what CK is (CPK - creatine phosphokinase), to understand what urea (urea), etc.

General information about blood biochemistry analysis - what it is and what you can learn by doing it, you will receive from this article. How much it costs to conduct such an analysis, how many days it takes to get results, should be found out directly in the laboratory where the patient intends to conduct this study.

How do you prepare for biochemical analysis?

Before donating blood, you need to carefully prepare for this process. Those who are interested in how to pass the test correctly need to take into account several fairly simple requirements:

• You need to donate blood only on an empty stomach;
• in the evening, on the eve of the upcoming analysis, you should not drink strong coffee, tea, consume fatty foods, or alcoholic beverages (it is better not to drink the latter for 2-3 days);
• do not smoke for at least an hour before the test;
• the day before the test, you should not practice any thermal procedures - go to the sauna, bathhouse, and also the person should not expose yourself to serious physical activity;
• laboratory tests must be taken in the morning, before any medical procedures;
• a person who is preparing for tests, upon arriving at the laboratory, should calm down a little, sit for a few minutes and catch his breath;
• the answer to the question of whether it is possible to brush your teeth before taking tests is negative: in order to accurately determine blood sugar, in the morning before the test you need to ignore this hygienic procedure, and also not drink tea and coffee;
• You should not take hormonal medications, diuretics, etc. before taking blood;
• two weeks before the study you need to stop taking medications that affect lipids in the blood, in particular statins ;
• if you need to take a full analysis again, this must be done at the same time, the laboratory must also be the same.

If a clinical blood test has been performed, the readings are deciphered by a specialist. Also, the interpretation of biochemical blood test results can be carried out using a special table, which indicates normal test results in adults and children. If any indicator differs from the norm, it is important to pay attention to this and consult with a doctor who can correctly “read” all the results obtained and give his recommendations. If necessary, blood biochemistry is prescribed: extended profile.

Interpretation table for biochemical blood tests in adults

Indicator in the study	Norm
Total protein	63-87 g/l
Protein fractions: albumin globulins (α1, α2, γ, β)
Creatinine	44-97 µmol per l – in women, 62-124 – in men
Urea	2.5-8.3 mmol/l
Uric acid	0.12-0.43 mmol/l - in men, 0.24-0.54 mmol/l - in women.
Total cholesterol	3.3-5.8 mmol/l
LDL	less than 3 mmol per l
HDL	greater than or equal to 1.2 mmol per L - in women, 1 mmol per L - in men
Glucose	3.5-6.2 mmol per l
Total bilirubin	8.49-20.58 µmol/l
Direct bilirubin	2.2-5.1 µmol/l
Triglycerides	less than 1.7 mmol per l
Aspartate aminotransferase (abbreviated as AST)	alanine aminotransferase - normal in women and men - up to 42 U/l
Alanine aminotransferase (abbreviated as ALT)	up to 38 U/l
Gamma glutamyl transferase (abbreviated GGT)	normal GGT levels are up to 33.5 U/l in men, up to 48.6 U/l in women.
Creatine kinase (abbreviated as KK)	up to 180 U/l
Alkaline phosphatase (abbreviated as ALP)	up to 260 U/l
α-amylase	up to 110 E per liter
Potassium	3.35-5.35 mmol/l
Sodium	130-155 mmol/l

Thus, a biochemical blood test makes it possible to conduct a detailed analysis to assess the functioning of internal organs. Also, decoding the results allows you to adequately “read” which macro- and microelements, needed by the body. Blood biochemistry makes it possible to recognize the presence of pathologies.

If you correctly decipher the obtained indicators, it is much easier to make any diagnosis. Biochemistry is a more detailed study than CBC. After all, deciphering the indicators of a general blood test does not allow one to obtain such detailed data.

It is very important to conduct such studies when. After all general analysis during pregnancy does not make it possible to get complete information. Therefore, biochemistry in pregnant women is prescribed, as a rule, in the first months and in the third trimester. In the presence of certain pathologies and poor health, this analysis is performed more often.

In modern laboratories they are able to conduct research and decipher the obtained indicators within a few hours. The patient is provided with a table containing all the data. Accordingly, it is even possible to independently monitor how normal blood counts are in adults and children.

Both the table for deciphering a general blood test in adults and biochemical tests are deciphered taking into account the age and gender of the patient. After all, the norm of blood biochemistry, like the norm of a clinical blood test, can vary in women and men, in young and elderly patients.

Hemogram is a clinical blood test in adults and children, which allows you to find out the amount of all blood elements, as well as their morphological features, ratio, content, etc.

Since blood biochemistry is a complex study, it also includes liver tests. Decoding the analysis allows you to determine whether liver function is normal. Liver parameters are important for diagnosing pathologies of this organ. The following data make it possible to assess the structural and functional state of the liver: ALT, GGTP (the GGTP norm in women is slightly lower), alkaline phosphatase, level and total protein. Liver tests are performed when necessary to establish or confirm the diagnosis.

Cholinesterase determined for the purpose of diagnosing the severity and condition of the liver, as well as its functions.

Blood sugar determined to assess the functions of the endocrine system. You can find out what a blood sugar test is called directly in the laboratory. The sugar symbol can be found on the results sheet. What is sugar called? It is referred to as "glucose" or "GLU" in English.

The norm is important CRP , since a jump in these indicators indicates the development of inflammation. Index AST indicates pathological processes associated with tissue destruction.

Index M.I.D. in a blood test, it is determined during a general analysis. The MID level allows you to determine the development of infectious diseases, anemia, etc. The MID indicator allows you to assess the condition immune system person.

ICSU is an indicator of the average concentration in . If MSHC is elevated, the reasons for this are associated with a deficiency of or, as well as congenital spherocytosis.

MPV - average value of the volume measured.

Lipidogram provides for the determination of indicators of total cholesterol, HDL, LDL, triglycerides. The lipid spectrum is determined to identify lipid metabolism disorders in the body.

Norm blood electrolytes indicates the normal course of metabolic processes in the body.

Seromucoid – this is a fraction of proteins, which includes a group of glycoproteins. Speaking about what seromucoid is, it should be taken into account that if the connective tissue is destroyed, degraded or damaged, seromucoids enter the blood plasma. Therefore, seromucoids are determined to predict development.

LDH, LDH (lactate dehydrogenase) - This is involved in the oxidation of glucose and the production of lactic acid.

Research on osteocalcin carried out for diagnostic purposes.

Analysis on ferritin (protein complex, the main intracellular iron depot) is carried out if hemochromatosis, chronic inflammatory and infectious diseases, tumors.

Blood test for ASO important for diagnosing types of complications after a streptococcal infection.

In addition, other indicators are determined, and other investigations are carried out (protein electrophoresis, etc.). The norm of a biochemical blood test is displayed in special tables. It displays the norm of a biochemical blood test in women; the table also provides information about normal values ​​in men. But still, about how to decipher a general blood test and how to read the data of a biochemical analysis, it is better to ask a specialist who will adequately evaluate the results in a comprehensive manner and prescribe the appropriate treatment.

Deciphering the biochemistry of blood in children is carried out by the specialist who ordered the studies. For this purpose, a table is also used, which indicates the norm for all indicators in children.

In veterinary medicine, there are also standards for biochemical blood parameters for dogs and cats - the corresponding tables indicate the biochemical composition of animal blood.

What some indicators mean in a blood test is discussed in more detail below.

Protein means a lot in the human body, as it takes part in the creation of new cells, in the transport of substances and the formation of humoral proteins.

The composition of proteins includes 20 main ones, they also contain inorganic substances, vitamins, lipid and carbohydrate residues.

The liquid part of the blood contains approximately 165 proteins, and their structure and role in the body are different. Proteins are divided into three different protein fractions:

• globulins (α1, α2, β, γ);
• fibrinogen .

Since protein production occurs mainly in the liver, their level indicates its synthetic function.

If a proteinogram indicates that there is a decrease in total protein levels in the body, this phenomenon is defined as hypoproteinemia. A similar phenomenon is observed in the following cases:

• during protein fasting - if a person follows a certain diet, practices vegetarianism;
• if there is increased excretion of protein in the urine - with kidney disease;
• if a person loses a lot of blood - with bleeding, heavy periods;
• in case of serious burns;
• with exudative pleurisy, exudative, ascites;
• with the development of malignant neoplasms;
• if protein formation is impaired - with hepatitis;
• when absorption of substances decreases – when , colitis, enteritis, etc.;
• after prolonged use of glucocorticosteroids.

An increased level of protein in the body is hyperproteinemia . There is a distinction between absolute and relative hyperproteinemia.

A relative increase in proteins develops in the event of loss of the liquid part of the plasma. This happens if you are worried about constant vomiting, with cholera.

An absolute increase in protein is noted if inflammatory processes or myeloma occur.

The concentrations of this substance change by 10% with changes in body position, as well as during physical activity.

Why do the concentrations of protein fractions change?

Protein fractions – globulins, albumins, fibrinogen.

A standard blood biotest does not involve the determination of fibrinogen, which reflects the blood clotting process. Coagulogram - analysis in which this indicator is determined.

When are protein levels elevated?

Albumin level:

• if fluid loss occurs during infectious diseases;
• for burns.

A-globulins:

• for systemic connective tissue diseases ( , );
• with purulent inflammation in acute form;
• for burns during the recovery period;
• nephrotic syndrome in patients with glomerulonephritis.

B-globulins:

• for hyperlipoproteinemia in people with diabetes;
• with a bleeding ulcer in the stomach or intestines;
• with nephrotic syndrome;
• at .

Gamma globulins are elevated in the blood:

• for viral and bacterial infections;
• for systemic connective tissue diseases (rheumatoid arthritis, dermatomyositis, scleroderma);
• for allergies;
• for burns;
• with helminthic infestation.

When is the level of protein fractions reduced?

• in newborns due to underdevelopment of liver cells;
• for lungs;
• during pregnancy;
• for liver diseases;
• with bleeding;
• in case of plasma accumulation in body cavities;
• for malignant tumors.

Not only cell construction occurs in the body. They also break down, and in the process, nitrogenous bases accumulate. They are formed in the human liver and are excreted through the kidneys. Therefore, if the indicators nitrogen metabolism elevated, then there is likely to be a dysfunction of the liver or kidneys, as well as excessive breakdown of proteins. Basic indicators of nitrogen metabolism – creatinine , urea . Ammonia, creatine, residual nitrogen, and uric acid are determined less frequently.

Urea (urea)

• glomerulonephritis, acute and chronic;
• nephrosclerosis;
• poisoning with various substances - dichloroethane, ethylene glycol, mercury salts;
• arterial hypertension;
• crash syndrome;
• polycystic disease or kidney;

Reasons causing the decrease:

• increased urine output;
• administration of glucose;
• liver failure;
• decrease in metabolic processes;
• starvation;
• hypothyroidism

Creatinine

Reasons for the increase:

• renal failure in acute and chronic forms;
• decompensated;
• acromegaly;
• muscle dystrophy;
• burns.

Uric acid

Reasons for the increase:

• leukemia;
• vitamin B-12 deficiency;
• acute infectious diseases;
• Vaquez disease;
• liver diseases;
• severe diabetes mellitus;
• skin pathologies;
• poisoning carbon monoxide, barbiturates.

Glucose

Glucose is considered the main indicator of carbohydrate metabolism. It is the main energy product that enters the cell, since the vital activity of the cell depends specifically on oxygen and glucose. After a person has eaten, glucose enters the liver, and there it is utilized in the form glycogen . These pancreatic processes are controlled - and glucagon . Due to a lack of glucose in the blood, hypoglycemia develops; its excess indicates that hyperglycemia is occurring.

Violation of blood glucose concentration occurs in the following cases:

Hypoglycemia

• with prolonged fasting;
• in case of malabsorption of carbohydrates - with enteritis, etc.;
• with hypothyroidism;
• for chronic liver pathologies;
• with chronic adrenal insufficiency;
• with hypopituitarism;
• in case of overdose of insulin or hypoglycemic drugs taken orally;
• with, insulinoma, meningoencephalitis, .

Hyperglycemia

• for diabetes mellitus of the first and second types;
• with thyrotoxicosis;
• in case of tumor development;
• with the development of tumors of the adrenal cortex;
• with pheochromocytoma;
• in people who practice treatment with glucocorticoids;
• at ;
• for injuries and brain tumors;
• with psycho-emotional agitation;
• if carbon monoxide poisoning occurs.

Specific colored proteins are peptides that contain metal (copper, iron). These are myoglobin, hemoglobin, cytochrome, cerulloplasmin, etc. Bilirubin is the end product of the breakdown of such proteins. When the existence of a red blood cell in the spleen ends, biliverdin reductase produces bilirubin, which is called indirect or free. This bilirubin is toxic, so it is harmful to the body. However, since its rapid connection with blood albumin occurs, poisoning of the body does not occur.

At the same time, in people who suffer from cirrhosis and hepatitis, there is no connection with glucuronic acid in the body, so the analysis shows a high level of bilirubin. Next, indirect bilirubin binds to glucuronic acid in liver cells, and it is converted into conjugated or direct bilirubin (DBil), which is not toxic. Its high level is observed when Gilbert's syndrome , biliary dyskinesias . If liver tests are performed, they may show high levels of direct bilirubin if liver cells are damaged.

Rheumatic tests

Rheumatic tests – a comprehensive immunochemical blood test, which includes a study to determine rheumatoid factor, an analysis of circulating immune complexes, and the determination of antibodies to o-streptolysin. Rheumatic tests can be carried out independently, as well as as part of studies that involve immunochemistry. Rheumatic tests should be performed if there are complaints of joint pain.

conclusions

Thus, a general therapeutic detailed biochemical blood test is a very important study in the diagnostic process. For those who want to conduct a full extended HD blood test or OBC in a clinic or laboratory, it is important to take into account that each laboratory uses a certain set of reagents, analyzers and other equipment. Consequently, the norms of indicators may differ, which must be taken into account when studying what a clinical blood test or biochemistry results show. Before reading the results, it is important to make sure that the form issued by the medical institution indicates the standards in order to interpret the test results correctly. The norm of OAC in children is also indicated on the forms, but a doctor must evaluate the results obtained.

Many people are interested in: blood test form 50 - what is it and why take it? This is a test to determine the antibodies that are in the body if it is infected. F50 analysis is done both when HIV is suspected and for the purpose of prevention in healthy person. It is also worth properly preparing for such a study.

Education: Graduated from Rivne State Basic Medical College with a degree in Pharmacy. Graduated from Vinnytsia State medical University them. M.I. Pirogov and internship at his base.

Experience: From 2003 to 2013, she worked as a pharmacist and manager of a pharmacy kiosk. She was awarded diplomas and decorations for many years of conscientious work. Articles on medical topics were published in local publications (newspapers) and on various Internet portals.

Guanosine triphosphate
Are common
Abbreviations	GTP, GTP
Traditional names	Guanosine triphosphate
Rat. formula	C 10 H 16 N 5 O 14 P 3
Physical properties
Molar mass	523.18 g/ mole
Classification
Reg. CAS number	86-01-1
SMILES	3(((O3)CO(=O)(O)O(=O)(O)OP(=O)(O)O)O)O)c(nc2=O)N]
Data are provided for standard conditions (25 °C, 100 kPa), unless otherwise stated.

Guanosine triphosphate(GTP, GTP) is purine nucleotide.

Biological role

GTP is a substrate for the synthesis RNA in progress transcriptions. The structure of GTP is similar to guanyl nucleoside, but is distinguished by the presence of three phosphate groups attached to the 5" carbon atom.

GTP takes part in reactions signal transmission, in particular associated with G proteins, and turns into GDF starring GTPases.

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Notes

Nitrogenous bases Nucleosides Nucleotides RNA DNA Analogues Types vectors

An excerpt characterizing Guanosine triphosphate

“Well, my friends, now I’ve thought about the whole matter and here’s my advice to you,” she began. – Yesterday, as you know, I was with Prince Nikolai; Well, I talked to him... He decided to shout. You can't shout me down! I sang everything to him!
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- Oh, no! – Natasha screamed.
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Ilya Andreich approved this proposal, immediately understanding its reasonableness. If the old man relents, then all the better it will be to come to him in Moscow or Bald Mountains, later; if not, then it will be possible to get married against his will only in Otradnoye.
“And the true truth,” he said. “I regret that I went to him and took her,” said the old count.
- No, why regret it? Having been here, it was impossible not to pay respects. Well, if he doesn’t want to, that’s his business,” said Marya Dmitrievna, looking for something in her reticule. - Yes, and the dowry is ready, what else do you have to wait for? and what’s not ready, I’ll send it to you. Although I feel sorry for you, it’s better to go with God. “Having found what she was looking for in the reticule, she handed it to Natasha. It was a letter from Princess Marya. - He writes to you. How she suffers, poor thing! She is afraid that you will think that she does not love you.
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“Don’t answer like that, mother,” she said. – What I say is true. Write an answer.
Natasha did not answer and went to her room to read Princess Marya’s letter.
Princess Marya wrote that she was in despair over the misunderstanding that had occurred between them. Whatever her father’s feelings, Princess Marya wrote, she asked Natasha to believe that she could not help but love her as the one chosen by her brother, for whose happiness she was ready to sacrifice everything.

The textbook is intended for students of the Biology major of all training profiles, all forms of training for theoretical preparation for classes, tests and exams. The manual covers the main sections of structural biochemistry: structure, physicochemical properties and functions of the main classes of biological macromolecules. Much attention is paid to a number of applied aspects of biochemistry.

Nucleotides and nucleic acids

Structure of nucleotides and nitrogenous bases

Nucleotides take part in many biochemical processes and are also monomers of nucleic acids. Nucleic acids provide all genetic processes. Each nucleotide is made up of three types of chemical molecules:

Nitrogenous base;

Monosaccharide;

1-3 residues of phosphoric acid.

Unlike monosaccharides, nucleotides as monomers are complex molecules consisting of structures belonging to different classes chemical substances, therefore it is necessary to consider the properties and structure of these components separately.

Nitrogenous bases

Nitrogen bases belong to heterocyclic compounds. In addition to carbon atoms, the heterocycle contains nitrogen atoms. All nitrogenous bases included in nucleotides belong to two classes of nitrogenous bases: purine and pyrimidine. Purine bases are derivatives of purine - a heterocycle consisting of two rings, one five-membered, the other six, numbered as shown in the figure. Pyrimidine bases are derivatives of pyrimidine and consist of one six-membered ring, numbering is also indicated in the figure (Figure 31). The main pyrimidine bases in both prokaryotes and eukaryotes are cytosine, thymine And uracil. The most common purine bases are adenine And guanine Two others – xanthine And hypoxanthine– are intermediates in their metabolic processes. In humans, the final product of purine catabolism is the oxidized purine base. - uric acid. In addition to the five major bases mentioned above, less widely represented minor bases are also known. Some of them are present only in the nucleic acids of bacteria and viruses, but many are also found in pro- and eukaryotic DNA and transport and ribosomal RNA. Thus, both bacterial and human DNA contain significant amounts of 5-methylcytosine; 5-hydroxymethylcytosine was found in bacteriophages. Unusual bases were identified in messenger RNA – N 6 -methyladenine, N 6, N 6 -dimethyladenine and N 7 -Methylguanine. In bacteria, a modified uracil with an (α-amino, α-carboxy)-propyl group attached at the N 3 position was also found. The functions of these substituted purines and pyrimidines are not fully understood, but they can form non-canonical bonds between bases (this will be discussed below), providing the formation of secondary and tertiary structures of nucleic acids.

Figure 31. Structure of nitrogenous bases

A series of purine bases with methyl substituents have been identified in plant cells. Many of them are pharmacologically active. Examples include coffee beans containing caffeine (1,3, 7-trimethylxanthine), tea leaves containing theophylline (1, 3-dimethylxanthine), and cocoa beans containing theobromine (3, 7-dimethylxanthine). dimethylxanthine).

isomerism and Physicochemical properties of purine and pyrimidine bases

A nitrogenous base molecule forms a system of alternating single and double bonds (a system of conjugated double bonds). This organization forms a rigid molecule, without the possibility of conformational transitions. As a result, we cannot talk about a change in the conformation of nitrogenous bases.

For nitrogenous bases, only one type of isomerism has been identified: the keto-enol transition or tautomerism.

Tautomerism

Due to the phenomenon of keto-enol tautomerism, nucleotides can exist in either lactam or lactam forms, with the lactam form predominant in guanine and thymine under physiological conditions (Figure 32). The importance of this circumstance will become clear when discussing the processes of base pairing.

Figure 32. Nucleotide tautomerism

Solubility

At neutral pH, guanine has the least solubility. Next in this series is xanthine. Uric acid in the form of urates is relatively soluble at neutral pH, but is very poorly soluble in liquids with lower pH values, such as urine. Guanine is normally absent in human urine, and xanthine and uric acid are its usual components. The last two purines are often found in urinary tract stones.

Light absorption

Due to the system of conjugated double bonds, all nitrogenous bases absorb in the ultraviolet part of the spectrum. Absorption spectrum is a graph of the distribution of optical density as a function of wavelength. Each nitrogenous base has its own absorption spectrum, from which it is possible to distinguish solutions of various nitrogenous bases or compounds that contain a nitrogenous base (nucleotides), but the absorption maximum for all coincides at a wavelength of 260 nm. This allows you to easily and quickly determine the concentration of both nitrogenous bases and nucleotides and nucleic acids. The absorption spectrum also depends on the pH of the solution (Figure 33).

Figure 33. Absorption spectra of various nitrogenous bases

Functions of nitrogenous bases

Nitrogenous bases are practically never found in a free state. The exceptions are some alkaloids and uric acid.

Nitrogenous bases perform the following functions:

Contains nucleotides;

Some alkaloids are nitrogenous bases, for example, caffeine in coffee or theopheline in tea;

Intermediate products of the exchange of nitrogenous bases and nucleotides;

Uric acid is the cause of urolithiasis;

Nitrogen is excreted as uric acid in some organisms.

Nucleotides and nucleosides

Nucleoside molecules are built from a purine or pyrimidine base, to which a carbohydrate (usually D-ribose or 2-deoxyribose) is attached via a β-bond in the N 9 or N 1 position, respectively. Thus, an adenine ribonucleoside (adenosine) consists of adenine and D-ribose attached at the N 9 position; guanosine– from guanine and D-ribose at position N 9; cytidine– from cytosine and ribose at position N1; uridine– from uracil and ribose in position N1. Thus, in purine nucleosides (nucleotides), the nitrogenous base and sugar are linked by a 1-9 β glycosidic bond, and in pyrimidines - by a 1-1 β glycosidic bond.

The composition of 2-deoxyribonucleosides includes purine or pyrimidine bases and 2-deoxyribose attached at the same N1 and N9 atoms. The attachment of ribose or 2́-deoxyribose to the ring structure of the base occurs through a relatively acid-labile N-glycosidic bond (Figure 34).

Nucleotides are nucleoside derivatives phosphorylated at one or more hydroxyl groups of a ribose (or deoxyribose) residue. Thus, adenosine monophosphate (AMP or adenylate) is built from adenine, ribose and phosphate. 2-deoxyadenosine monophosphate (dAMP or deoxyadenylate) is a molecule consisting of adenine, 2-deoxyribose and phosphate. Usually, ribose is attached to uracil, and 2-deoxyribose is attached to thymine. Therefore, thymidylic acid (TMF) consists of thymine, 2́-deoxyribose and phosphate. In addition to the above-mentioned forms of nucleotides, nucleotides of unusual structure were also discovered. Thus, in the tRNA molecule, a nucleotide was identified in which ribose is attached to uracil in the fifth position, i.e., not by a nitrogen-carbon bond, but by a carbon-carbon bond. The product of this unusual addition is called pseudouridine (ψ). tRNA molecules also contain another unusual nucleotide structure - thymine combined with ribose monophosphate. This nucleotide is formed after the synthesis of the tRNA molecule by methylation of the UMP residue with S-adenosylmethionine. Pseudouridylic acid (ψMP) is also formed as a result of UMP rearrangement after tRNA synthesis.

Figure 34. Structure of purine and pyrimidine nucleosides and nucleotides

Nomenclature, physicochemical properties and functions of nucleosides and nucleotides

The position of the phosphate group in the nucleotide molecule is indicated by a number. For example, adenosine with a phosphate group attached to the 3rd carbon of ribose would be designated 3́-monophosphate. A prime is placed after the number to distinguish the carbon number in the purine or pyrimidine base from the position of this atom in the deoxyribose residue. When numbering the carbon atoms of the base, there is no prime. The nucleotide 2-deoxyadenosine with a phosphate residue at carbon-5 of the sugar molecule is designated 2-deoxyadenosine-5-monophosphate. Nucleosides containing adenine, guanine, cytosine, thymine and uracil are usually designated by the letters A, G, C, T and U, respectively. The presence of the letter d (or d) before the abbreviation indicates that the carbohydrate component of the nucleoside is 2́-deoxyribose. Guanosine containing 2-deoxyribose can be designated dG (deoxyguanosine), and the corresponding monophosphate with a phosphate group attached to the third carbon atom of deoxyribose is dG-3-MF. Typically, in cases where a phosphate is attached to the 5 carbon of ribose or deoxyribose, the symbol 5́ is omitted. Thus, guanosine 5-monophosphate is usually denoted as GMP, and 2-deoxyguanosine 5-monophosphate is abbreviated as dGMP. If 2 or 3 phosphoric acid residues are attached to a carbohydrate residue of a nucleoside, the abbreviations DP (diphosphate) and TP (triphosphate) are used. Thus, adenosine + triphosphate with three phosphate groups at the 5́ position of the carbohydrate would be designated ATP. Since phosphates in nucleotide molecules are in the form of phosphoric acid anhydrides, i.e., in a state with low entropy, they are called macroergs (possessing a large reserve of potential energy). When 1 mole of ATP is hydrolyzed to ADP, 7.3 kcal of potential energy is released.

Figure 35. Structure of cAMP

Physicochemical properties of nucleotides

Since nucleotides contain nitrogenous bases, properties such as tautomerism and the ability to absorb in the ultraviolet part of the spectrum are also characteristic of nucleotides, and the absorption spectra of nitrogenous bases and nucleotides containing these bases are similar. The presence of sugar and phosphoric acid residues makes them more hydrophilic than nitrogenous bases. All nucleotides are acids because they contain phosphoric acid residues.

Functions of natural nucleotides

Nucleotides are monomers of nucleic acids (RNA, DNA). DNA contains deoxyribonucleotide phosphates - derivatives of adenine, thymine, guanine and cytosine. Also, some guanine and cytosine molecules in DNA are methylated, that is, they contain a methyl group. The main monomers in RNA include ribonucleotide phosphates - derivatives of adenine, uracil, guanine and cytosine. RNA also contains nucleotides containing various minor nitrogenous bases, for example xanthine, hypoxanthine, dihydrouridine, etc.

Nucleotides are monomers of coenzymes (NAD, NADP, FAD, co-enzyme A, methionine-adenosine). As part of coenzymes, they participate in enzymatic reactions. This function will be discussed in more detail below.

Energy (ATP). ATP functions as the main intracellular transporter free energy. The concentration of the most abundant free nucleotide in mammalian cells, ATP, is about 1 mmol/L.

Signal (cGMP, cAMP)(Figure 35). Cyclic AMP (3-, 5-adenosine monophosphate, cAMP), a mediator of various extracellular signals in animal cells, is formed from ATP as a result of a reaction catalyzed by adenylate cyclase. The activity of adenylate cyclase is regulated by a complex of interactions, many of which are initiated through hormone receptors. The intracellular concentration of cAMP (about 1 µmol/l) is 3 orders of magnitude lower than the concentration of ATP. Cyclic cGMP (3-, 5-guanosine monophosphate, cGMP) serves as an intracellular conductor of extracellular signals. In some cases, cGMP acts as a cAMP antagonist. cGMP is formed from GTP by the action of guanylate cyclase, an enzyme that has much in common with adenylate cyclase. Guanylate cyclase, like adenylate cyclase, is regulated by various effectors, including hormones. Like cAMP, cGMP is hydrolyzed by phosphodiesterase to the corresponding 5-monophosphate.

Regulatory (GTF). The activity of a group of proteins (G-proteins) that mainly perform regulatory function, depends on what nucleotide they bind. In their inactive form, these proteins bind GDP; when the protein is activated, GDP is replaced by GTP. When performing its function, the protein hydrolyzes GTP to GDP and phosphate, the energy released is spent on the functioning of the protein.

Activation in the metabolism of lipids and monosaccharides (UTP, STP). Derivatives of uracil nucleotides participate as activating agents in the reactions of hexose metabolism and carbohydrate polymerization, in particular in the biosynthesis of starch and oligosaccharide fragments of glycoproteins and proteoglycans. The substrates in these reactions are uridine diphosphate sugars. For example, uridine diphosphate glucose serves as a precursor to glycogen. Also, the conversion of glucose into galactose, glucuronic acid or other monosaccharide derivatives occurs in the form of a conjugate with UDP. STP is necessary for the biosynthesis of some phosphoglycerides in animal tissues. Reactions involving ceramide and CDP-choline lead to the formation of sphingomyelin and other substituted sphingosines.

Participation in the decontamination of various alcohols and phenols(UDP-glucuronic acid). Uridine diphosphate glucuronic acid - performs the function of an “active” glucuronide in conjugation reactions, for example, in the formation of bilirubin glucuronide.

Nucleotides in coenzymes

Coenzymes are low-molecular compounds associated with enzymes (see section “Enzymes”) directly involved in a biochemical reaction, in other words, they are another substrate that is not released into the environment.

Coenzymes are divided into two groups:

carriers of protons and electrons, these coenzymes are involved in redox reactions;

Transporters of all other groups except protons and electrons, these coenzymes are involved in transferase reactions.

The mechanisms of these reactions can be considered in more detail in the chapter “Enzymes”.

Some coenzymes contain nucleotides. They are also divided into these same two groups.

Coenzymes transport protons and electrons

These coenzymes participate in redox reactions, where adenosine performs only a structural function; nucleotides containing other types of bases enter into the reaction; two types of such coenzymes are distinguished: nicotinic and flavin. They differ not only in their active grouping, but also in the type of reactions they carry out.

Nicotine coenzymes

Figure 36. Nicotine coenzymes. A-structure of NAD, B-structure of NADP, B-mechanism of activity of nicotinic acid, G-mechanism of nicotinic coenzymes

Nicotinamide adenine dinucleotide (NAD+) is the main electron acceptor during the oxidation of fuel molecules. The reactive part of NAD+ is its nicotinamide ring. When a substrate is oxidized, the nicotinamide ring of NAD+ adds a hydrogen ion and two electrons, which are equivalent to a hydride ion. The reduced form of this transporter is NADH. During this dehydrogenation, one hydrogen atom of the substrate is directly transferred to NAD + , while the second is transferred to the solvent. Both electrons lost by the substrate are transferred to the nicotinamide ring. The role of the electron donor in most processes of reductive biosynthesis (plastic metabolism); performs the reduced form of nicotine amide adenine dinucleotide phosphate (NADPH). NADPH differs from NAD by the presence of a phosphate linked by an ester bond to the 2́-hydroxyl group of adenosine. The oxidized form of NADPH is designated NADP+. NADPH transfers electrons in the same way as NADH. However, NADPH is used almost exclusively in reductive biosynthetic processes, while NADH is used primarily to generate ATP. The additional phosphate group of NADPH is the site responsible for the molecule's intended purpose of being recognized by enzymes.

Flavin coenzymes

The first flavin coenzyme (flavin mononucleotide FMN) was isolated by A. Szent-Györgyi from cardiac muscle in 1932, and R. G. Warburg and V. Christian at the same time obtained the first flavoprotein containing FMN as a coenzyme from yeast. The second most important flavin coenzyme, flavin adenine dinucleotide (FAD), was isolated by them as a cofactor of D-amino acid oxidase in 1938. Due to the redox transformation of the flavin ring, flavin coenzymes carry out redox reactions as part of many important enzyme systems: oxidases (in particular, D- and L-amino acid oxidases, monoamine oxidase, which regulates the level of catecholamines in the blood) and dehydrogenases (often involving nicotinamide adenine dinucleotide and ubiquinones).

Figure 37. Flavin coenzymes. A-structure of FAD, B-mechanism of nicotinic acid activity, B-mechanism of flavin coenzymes

The second main electron carrier during the oxidation of fuel molecules is flavin adenine dinucleotide. The abbreviations used to designate the oxidized and reduced forms of this transporter are FAD and FADH 2, respectively. The reactive part of FAD is its isoalloxazine ring. FAD, like NAD+, gains two electrons. However, FAD, unlike NAD+, attaches both hydrogen atoms lost by the substrate.

End of introductory fragment.