Endopeptidase or endoproteinase are peptidases that break peptide bonds within the molecule, in contrast to exopeptidases, which break peptide bonds from their end-pieces. Thus, endopeptidases cleave peptides.
They are usually very specific for certain amino acids.
Examples of endopeptidases include:
- Trypsin - cuts after Arg or Lys, unless followed by Pro. Very strict.
- Chymotrypsin - cuts after Phe, Trp, or Tyr, unless followed by Pro. Cuts more slowly after Asn, His, Met or Leu.
- Elastase - cuts after Ala, Gly, Ser, or Val, unless followed by Pro.
- Thermolysin - cuts before Ile, Met, Phe, Trp, Tyr, or Val, unless preceded by Pro. Sometimes cuts after Ala, Asp, His or Thr. Heat stable.
- Pepsin - cuts before Leu, Phe, Trp or Tyr, unless preceded by Pro. Also others, quite nonspecific; works best at pH 2.
- Endopeptidase V8 - cuts after Glu.