Exoprotease

Part of speech: noun

Definitions

1. An enzyme that catalyzes the removal of amino acids from the ends of protein chains; a biological catalyst that breaks peptide bonds at the terminal regions of polypeptides; a protein-degrading agent that specifically cleaves amino acids outward from the ends of proteins
2. A type of enzyme functioning to cleave amino acids from the terminal ends of protein molecules; a catalytic protein that hydrolyzes peptide bonds at protein extremities; a biochemical agent that digests proteins starting from their ends rather than internal sections
3. An enzyme responsible for sequential cleavage of amino acids from protein termini; a proteolytic enzyme that acts on the end portions of polypeptides to release amino acids; a protein enzyme that targets peptide bonds at the outermost ends of protein chains for hydrolysis

Etymology: Exoprotease is a plain technical compound: "exo-", from Greek "exo" meaning "outside" or "outward", joined to "protease", an enzyme that breaks down proteins by cutting the peptide bonds between their amino acids. Together the word names the subset of these enzymes that work only at the ends of a protein chain, snipping off one residue at a time from the terminus rather than cutting through the middle. The contrast with "endoprotease" makes the prefix meaningful. Endoproteases, from Greek "endo" meaning "within", attack internal bonds, while exoproteases nibble from the outside in. Biochemists use the pair to classify enzymes by where they act on a chain, and aminopeptidases and carboxypeptidases are the usual examples of exoproteases, distinguished by which end of the chain they attack.

Synonyms: extracellular protease, secreted protease