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.
See also: IUPAC numerical multiplier

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.

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