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noun, plural: nonapeptides

An oligopeptide comprised of nine amino acid residues


Peptides are monomers of amino acids that are bounded together in chains through an amide bond between the carboxyl group of one amino acid and the amine group of the adjacent amino acid. Peptides can be classified according to the number of amino acid residues in a chain. For instance, a dipeptide is a peptide comprised of two amino acid residues whereas a tripeptide is a peptide consisting of three amino acid residues. Thus, a nonapeptide is a peptide chain of nine amino acid residues. The term oligopeptide pertains to a peptide formed by a chain of fewer (i.e. two to twenty) amino acid residues in contrast to the term polypeptide that is made up of several amino acid residues. Therefore, a nonapeptide is an oligopeptide. An example of a nonapeptide is the bradykinin. Bradykinin is a nonapeptide (RPPGFSPFR) that is formed through the action of proteases on kininogens. It is a potent vasodilator. It increases the permeability of post capillary venules.

Word origin: Latin nonus ‎(ninth) + Ancient Greek peptós (digested) See also: