Peptide - Notes On Terminology

Notes On Terminology

Length:

• A polypeptide is a single linear chain of amino acids.
• A protein is one or more polypeptides more than about 50 amino acids long.
• An oligopeptide (or simply a peptide) is a polypeptide less than 30-50 amino acids long.

Number of amino acids:

• A monopeptide has one amino acid.
• A dipeptide has two amino acids.
• A tripeptide has three amino acids.
• A tetrapeptide has four amino acids.
• A pentapeptide has five amino acids.
• A hexapeptide has six amino acids.
• A heptapentide has seven amino acids.
• An octapeptide has eight amino acids (e.g., angiotensin II).
• A nonapeptide has nine amino acids (e.g., oxytocin).
• A decapeptide has ten amino acids (e.g., gonadotropin-releasing hormone & angiotensin I).
• An undecapeptide (or monodecapeptide) has eleven amino acids, a dodecapeptide (or didecapeptide) has twelve amino acids, a tridecapeptide has thirteen amino acids, and so forth.
• An icosapeptide has twenty amino acids, a tricontapeptide has thirty amino acids, a tetracontapeptide has forty amino acids, and so forth.

Function:

• A neuropeptide is a peptide that is active in association with neural tissue.
• A lipopeptide is a peptide that has a lipid connected to it, and pepducins are lipopeptides that interact with GPCRs.
• A peptide hormone is a peptide that acts as a hormone.
• A proteose is a mixture of peptides produced by the hydrolysis of proteins. The term is somewhat archaic.