Mainly in the liver: include the following processes:
1. Oxidative deamination: The first step, dehydrogenation, the formation of imine; the second step, hydrolysis. The resulting H2O2 is toxic, and under the catalysis of catalase, H2O and O2 are generated to release the poison to the cells.
2. Non-oxidative deamination: 1 Reductive deamination (strictly anaerobic conditions); 2 Hydrolysis and deamination; 3 Dehydration and deamination; 4 Deoximation deamination; 5 Oxidation-reduction deamination, oxidation and reduction of two amino acids The reaction produces organic acids, keto acids, ammonia; 6 deamidation.
3. Transamination. Transamination is an important method for deamination of amino acids. Except Gly, Lys, Thr, and Pro, most amino acids can participate in transamination. Transfer of amino acids between α-amino acids and α-keto acids results in the production of the corresponding keto acids from the original amino acids, whereas the original keto acids generate the corresponding amino acids.
4. Combined deamination: The amino group can not be finally removed by the transamination alone, and the oxidative deamination can not meet the need of deamination. The body can remove amino quickly with the help of combined deamination: 1. Combined deamination with glutamate dehydrogenase as the center. 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 produce α-ketoglutarate under the catalysis of L-Glu deamination. ammonia. 2, through the purine nucleotide cycle combined deamination. Skeletal muscle, myocardium, liver, and brain are mainly purine nucleotide recycling.
Most amino acids in the body can undergo decarboxylation to produce 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. For example, decarboxylation of L-Glu in brain tissue to r-aminobutyric acid is an important neurotransmitter. His decarboxylation to histamine (also known as histamine), has the effect of lowering blood pressure. Decarboxylation of Tyr to tyramine has the effect of increasing blood pressure. However, most amines are toxic to animals and have amine oxidases in their bodies that can 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 the promotion of growth, normal metabolism, and maintenance of life. If the human body lacks or reduces one of them, the body's normal life metabolism will be hindered, and even lead to the occurrence of various diseases or life activities.