peptide

/pep"tuyd/, n. Biochem.

a compound containing two or more amino acids in which the carboxyl group of one acid is linked to the amino group of the other.

[1905-10; PEPT(IC) + -IDE]

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Organic compound composed of a series of amino acids linked by peptide bonds (see covalent bond) between a carbon atom of one and a nitrogen atom of the next.

Peptide chains longer than a few dozen amino acids are called proteins. Biosynthesis of peptides from a succession of amino acids carried by transfer RNA molecules takes place on ribosomes and is catalyzed and controlled by enzymes. Many hormones, antibiotics, and other compounds that participate in life processes are peptides.

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▪ chemical compound

      any organic substance of which the molecules are structurally like those of proteins, but smaller. The class of peptides includes many hormones, antibiotics, and other compounds that participate in the metabolic functions of living organisms. Peptide molecules are composed of two or more amino acids joined through amide formation involving the carboxyl group of each amino acid and the amino group of the next. The chemical bond between the carbon and nitrogen atoms of each amide group is called a peptide bond. Some or all of the peptide bonds, which connect the consecutive triplets of atoms in the chain regarded as the backbone of the molecule, can be broken by partial or complete hydrolysis of the compound. This reaction, producing smaller peptides and finally the individual amino acids, is commonly used in studies of the composition and structure of peptides and proteins.

      The number of amino-acid molecules present in a peptide is indicated by a prefix: a dipeptide contains two amino acids; an octapeptide, eight; an oligopeptide, a few; a polypeptide, many. The distinction between a polypeptide and a protein is imprecise and largely academic; some authorities have adopted, as an upper limit on the molecular weight of a polypeptide, 10,000 (that of a peptide composed of about 100 amino acids).

Additional Reading

An overview of peptides is found in Donald Voet and Judith G. Voet, Biochemistry, 3rd ed. (2004); and Theodor Wieland and Miklos Bodanszky, The World of Peptides (1991). Peptide synthesis is covered in Miklos Bodanszky, Principles of Peptide Synthesis, 2nd rev. ed. (1993); and N. Leo Benoiton, Chemistry of Peptide Synthesis (2006).

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