Thanks to aminotransferases, NH2 groups are transferred from the donor Ξ³-amino acid to the acceptor, the Ξ±-amino acid, without the intermediate formation of ammonium. That is, transamination (reamination: the reversible transfer of amino groups to keto acids) is a process discovered by famous Russian scientists Braunstein and Kritsman.
Amino acids (aspartic, glutamic and alanine) during transamination are converted into the corresponding Ξ±-keto acids, which are components of the tricarboxylic acid cycle. When they are oxidized in the Krebs cycle, they serve as a source of energy.
Transamination is essential in providing the urea cycle with aspartate.
Despite the fact that aromatic amino acids, such as phenylalanine, tyrosine and tryptophan, can undergo transamination reactions, only the determination of the activity of aspartate and alanine aminotransferases has found practical application in medicine. These enzymes are widely distributed in the tissues of the human body.
Alanine aminotransferase is elevated in red blood cells and its concentration is six times higher than that in serum. The highest concentration of this enzyme is recorded in the tissues of the liver.
Alanine aminotransferase is not the same for the tissues of the human body. So, for example, the enzyme activity in heart tissues is 7.1 (E * 10-3 g of homogenate tissue), in the liver - 44, skeletal muscle - 4.8, kidneys - 19, spleen - 1.2, lungs 0.7 and blood serum - 0.016. Existing methods for determining the activity of aminotransferases in blood serum are divided into two groups: the end point (colorimetric, using conventional photometric equipment not equipped with thermostated cuvettes) and kinetic (spectrophotometric).
B6 is a common vitamin in a variety of foods. However, it should be remembered that during the cooking process (thermal curing) this vitamin is destroyed. Pyridoxine is a cofactor of most enzymes. The concentration of pyrodoxin-5-phosphate in the blood decreases with age. Therefore, the activity of an enzyme such as alanine aminotransferase is reduced in people older than 64 years (approximately 30%) than in those aged 46β63 years. The concentration of vitamin B6 in serum determines the activity of alanine aminotransferase.
To determine the functional state of the liver, the level of aminotransferases in the patient's blood is often examined. This is primarily due to the fact that a change in their activity occurs much faster than other laboratory indicators. The elimination (exit) of liver enzymes into the blood is a sign of cytolysis - the destruction of cells or the violation of the permeability of their membranes. When analyzing changes in enzyme activity, it is important to establish the elimination site. To do this, you need to know their activity in the blood and cells of a healthy body, intracellular localization and metabolism. The concentration of the enzyme, alanine aminotransferase, is increased, especially in liver cells, so even a slight damage to them provokes an increase in the activity of the enzyme in the blood. Given the activity of the enzyme, liver diseases (hepatitis, hepatosis) are diagnosed.
Alanine aminotransferase is elevated with liver necrosis, as well as with parenchymal hepatitis. A low concentration of the enzyme is recorded in chronic hepatitis and dystrophy. It should be noted that an increase in the activity of aminotransferase in blood serum begins 3β8 days before the appearance of the main clinical signs of the disease and reaches maximum values ββin the first days of the development of the pathological process.
So, alanine aminotransferase is increased: cirrhosis, obstructive jaundice, liver cancer, myocardial infarction, heart failure, hypoxia, shock, myositis, myocarditis, fatty hepatosis, pancreatin, chronic alcoholism.