Amino acid metabolism encompasses the various biochemical processes involved in the synthesis, breakdown, and interconversion of amino acids, which are the building blocks of proteins.
Amino acid metabolism is crucial for maintaining cellular function, growth, and repair.
It can be broadly classified into two categories:
1. Anabolism:
The synthesis of amino acids and proteins from simpler precursors.
There are 20 standard amino acids, 11 of which can be synthesized by the human body (non-essential amino acids) and 9 that must be obtained through diet (essential amino acids).
The process of protein synthesis, known as translation, occurs at ribosomes and involves the use of mRNA, tRNA, and aminoacyl-tRNA synthetases.
2. Catabolism:
The breakdown of amino acids and proteins for energy production, the generation of metabolic intermediates, or the removal of excess nitrogen.
General Reactions in Amino Acid Metabolism:
1. Transamination:
Process: Transfer of an amino group from one amino acid to a keto acid.
Enzyme: Transaminase (aminotransferase).
Importance: Produces new amino acids and plays a role in nitrogen balance.
2. Deamination:
Process: Removal of an amino group from an amino acid, producing a keto acid and ammonia (NH3).
Types: Oxidative deamination (common in liver) and non-oxidative deamination.
Importance: Converts amino acids into usable energy and removes excess nitrogen.
3. Decarboxylation:
Process: Removal of a carboxyl group (-COOH) from an amino acid, releasing carbon dioxide (CO2).
Enzyme: Decarboxylases.
Importance: Produces bioactive amines and neurotransmitters, such as dopamine, serotonin, GABA, and histamine.
These reactions are fundamental for utilizing amino acids in various physiological processes, including energy production, neurotransmitter synthesis, and maintaining nitrogen balance.