Exopeptidase

Part of speech: noun

Definitions

1. An enzyme responsible for catalyzing the hydrolysis of peptide bonds at the ends of protein chains
2. A type of protease that removes amino acids from the terminal end of peptides
3. A biochemical catalyst that facilitates the breakdown of peptides into individual amino acids by cleaving terminal peptide bonds

Etymology: The word is a technical coinage built from three parts, each with its own history. "Exo-" comes from the Greek "exō," meaning "outside" or "outward," and in chemistry it marks action at the outer end of a molecule. "Peptide" was coined in the late 19th century from the Greek "pepsis," meaning "digestion," on the model of "protein" and similar terms, to name short chains of amino acids linked by peptide bonds. The suffix "-ase," used for enzymes, was modeled on "diastase," the first enzyme identified, discovered in 1833 by Anselme Payen and Jean-François Persoz, whose name was itself shaped by the Greek "diastasis," meaning "separation." Put together, the parts describe the enzyme's job exactly: an "exopeptidase" works from the ends of a peptide chain, snipping off one amino acid at a time, rather than cutting the chain in its middle as an "endopeptidase" does. The name was assembled by biochemists working in the 20th century, so it is a modern construction from classical building blocks rather than a term used by the ancient Greeks.

Synonyms: peptidase, carboxypeptidase, aminopeptidase