Thanks to aminotransferases carried outtransfer of NH2-groups from the donor γ-amino acid to the acceptor - α-amino acid without intermediate formation of ammonium. That is, transamination (transamination: reversible transfer of amino groups to keto acids) is a process discovered by well-known Russian scientists Braunstein and Kritzman.
Amino acids (aspartic, glutamic andalanine) in the process of transamination is converted into the corresponding α-keto acids, which are components of the tricarboxylic acid cycle. When oxidized in the Krebs cycle, they serve as a source of energy.
Transamination is also essential in providing the urea cycle with aspartate.
Although transamination reactionsaromatic amino acids can also be exposed: phenylalanine, tyrosine and tryptophan; practical application in medicine has found only a definition of the activity of aspartate and alanine aminotransferase. These enzymes are widely distributed in the tissues of the human body.
Alanine aminotransferase is increased in erythrocytes and its concentration is six times higher than that in serum. The highest concentration of this enzyme is fixed in the tissues of the liver.
Аланинаминотрансфераза норма для тканей the human body is not the same. So, for example, the enzyme activity in the heart tissues is 7.1 (E * 10-3 g of homogenate tissue), in the liver - 44, skeletal muscle - 4.8, kidney - 19, spleen - 1.2, lung 0.7 and serum - 0,016. Existing methods for determining the activity of aminotransferases in serum are divided into two groups: end points (colorimetric, using conventional photometric equipment not equipped with thermostatted cells) and kinetic (spectrophotometric).
B6 is a common vitamin invariety of foods. However, it should be remembered that in the process of cooking (thermal processing), this vitamin is destroyed. Pyridoxine is a cofactor of most enzymes. The concentration of pyrodoxine-5-phosphate in the blood decreases with age. Therefore, the activity of such an enzyme as alanine aminotransferase is reduced in people over 64 years old (approximately 30%) than at the age of 46–63 years. The concentration of vitamin B6 in serum causes the activity of alanine aminotransferase.
To determine the functional state of the liververy often examine the level of aminotransferases in the patient's blood. This is primarily due to the fact that the change in their activity occurs much faster than other laboratory indicators. Elimination (release) of liver enzymes into the blood is a sign of cytolysis - cell destruction or impaired permeability of their membranes. When analyzing changes in enzyme activity, it is important to establish the place of elimination. For this, it is necessary to know their activity in the blood and cells of a healthy organism, the intracellular localization and metabolism. The concentration of the enzyme - alanine aminotransferase is increased, especially in the liver cells; therefore, even their minor damage provokes an increase in the activity of the enzyme in the blood. Taking into account the activity of the enzyme, liver diseases are diagnosed (hepatitis, hepatosis).
Alanine aminotransferase increased with necrosisliver, as well as parenchymal hepatitis. Low enzyme concentrations are recorded for chronic hepatitis and dystrophy. It should be said that the increase in serum aminotransferase activity begins 3–8 days before the appearance of the main clinical signs of the disease and reaches maximum values in the first days of the development of the pathological process.
So, alanine aminotransferase increased:liver cirrhosis, obstructive jaundice, liver cancer, myocardial infarction, right heart failure, hypoxia, shock, myositis, myocarditis, fatty hepatosis, pancreatin, chronic alcoholism.
