The following points highlight the fourteen important functions of amino acids.
(1) They are building blocks of proteins and enzymes.
(2) Storage of nitrogen occurs in the form of amides.
(3) Amino acid glycine provides nitrogen and carbon atoms for the synthesis of protoporphyrin and heme (= haem).
(4) Tryptophan produces plant hormone indole 3-acetic acid or IAA and vitamin nicotinamide.
(5) Amino acid tyrosine gives rise to two hormones (thyroxine and adrenaline) and skin pigment melanin.
(6) P-alanine, a derivative of asparate, takes part in the formation of coenzyme A and pantothenic acid (a vitamin).
(7) Histamine is derived from amino acid histidine through decarboxylation. Histamine is required for optimum functioning of muscles, blood capillaries and gastric secretion but in excess it causes anaphylaxis.
(8) Some amino acids act as donors of methyl group in the synthesis of various organic compounds including alkaloids, e.g., methionine.
(9) Ornithine and citrulline are components of urea cycle.
(10) Diaminopimelic acid, an intermediate of lysine synthesis, is a component of prokaryotic cell wall.
(11) Many non-protein amino acids are components of antibiotics.
(12) Small peptides are associated with structural units of prokaryotic wall called peptidoglycans (= mucopeptides).
(13) Enkephalins are pentapeptides produced by nerve cells. They function as body opiates influencing perception of pleasure and pain.
(14) Excess amino acids are deaminated in liver. The organic acids are changed to glucose (gluconeogenesis) or used directly in metabolism.