The specific ways in which amino acids are involved in metabolism are as follows:
Mainly in the liver: including the following processes:
(1) Oxidative deamination: the first step, dehydrogenation, to form an imine; the second step, hydrolysis. The produced H2O2 is toxic, and under the catalysis of catalase, H2O and O2 are formed to release the toxicity to the cells.
(2) Non-oxidative deamination: 1 reduction deamination (under strict anaerobic conditions); 2 hydrolysis deamination; 3 dehydration deamination; 4 deamination deamination; 5 oxidation-reduction deamination, two amino acids oxidize each other Reduction reaction, the formation of organic acids, keto acids, ammonia; 6 deamidation.
(3) Transamination. Transamination is an important way to deamination of amino acids. Except Gly, Lys, Thr and Pro, most amino acids can participate in transamination. Aminotransfer occurs between the α-amino acid and the α-keto acid, and as a result, the original amino acid produces the corresponding keto acid, and the original keto acid produces the corresponding amino acid.
(4) Combined deamination: The amino group alone cannot finally remove the amino group, and the oxidative deamination alone cannot meet the needs of the body for deamination. The body can rapidly remove the amino group by means of combined deamination: 1. Combined deamination centered on glutamate dehydrogenase. The α-amino group of the amino acid is first transferred to α-ketoglutaric acid to form the corresponding α-keto acid and Glu, and then deaminated to form α-ketoglutaric acid under the catalysis of L-Glu deaminase, and released. ammonia. 2. Through the combined deamination of the purine nucleotide cycle. Skeletal muscle, myocardium, liver, and brain are mainly in the form of purine nucleotides.
Most of the amino acids in the organism can be decarboxylated to form the corresponding primary amine. Amino acid decarboxylase is highly specific, each amino acid has a decarboxylase, and the coenzyme is pyridoxal phosphate. Amino acid decarboxylation reactions are widely found in animals, plants and microorganisms. Some products have important physiological functions, such as decarboxylation of L-Glu in brain tissue to produce r-aminobutyric acid, which is an important neurotransmitter. His decarboxylation produces histamine (also known as histamine) and has a blood pressure lowering effect. Decarboxylation of Tyr produces tyramine, which has the effect of raising blood pressure. However, most amines are toxic to animals, and there are amine oxidases in the body that oxidize amines to aldehydes and ammonia.
Therefore, the presence of amino acids in the human body not only provides an important raw material for the synthesis of proteins, but also provides a material basis for promoting growth, normal metabolism, and life support. If the human body lacks or reduces one of them, the normal life metabolism of the human body will be impeded, and even the occurrence of various diseases or the termination of life activities.