Twoaminoacid

Twoaminoacid is not a standard term in biochemistry, but it is commonly used informally to refer to a dipeptide: a molecule composed of two amino acids linked by a single peptide bond. In formal terminology, such molecules are simply called dipeptides.

Structure and nomenclature: A dipeptide has the general skeleton H2N-CHR-CO-NH-CHR'-COOH, where R and R' are the side chains of the two constituent amino acids. The N-terminus (free amino group) and C-terminus (free carboxyl group) may be designated in the name from left to right, for example glycylglycine (Gly-Gly) or alanyl-glycine (Ala-Gly). When both residues are chiral, dipeptides can exist as different stereoisomers and conformers, with the peptide bond itself typically adopting a trans configuration in solution.

Formation and hydrolysis: Dipeptides arise by condensation between the carboxyl group of one amino acid and the amino group of the second, releasing water. In biological systems, dipeptides are often produced as intermediates during protein digestion, where specific dipeptidases hydrolyze them into free amino acids. Dipeptides can also be prepared synthetically by solid-phase peptide synthesis for research or therapeutic purposes.

Examples and functions: Common examples include diglycine (Gly-Gly), glycylglycine, and alanyl-glycine (Ala-Gly). Some dipeptides, such as carnosine (β-alanine-histidine) and anserine, have particular roles as antioxidants or signaling molecules. Dipeptides are studied as substrates for peptidases and as nutritional supplements, due to their solubility and potential bioavailability advantages.

See also: peptide bond, amino acid, dipeptide, proteolysis.