Author(s): Rupa Singh
Proteases form a large group of enzymes belonging to the class of Hydrolases, ubiquitous in nature and occupy a major role with respect to their application in both physiological and commercial fields. They are molecules of relatively small size and are compact, spherical structures that catalyze the cleavage of peptide bonds in proteins. Based on the functional group present at the active site and their catalytic mechanism, proteases are classified into four groups: serine proteases, aspartic proteases, cysteine / thiol proteases, and metalloproteases (Jewell, 2000). Depending on their site of action, proteases are broadly divided into either exopeptidases or endopeptidases. Endopeptidases (like: trypsin, chymotrypsin, pepsin, papain) cleave the peptide bonds distant from the termini of a substrate, whereas exopeptidases (like: aminopeptidases, carboxypeptidases A) cleaves the peptide bond proximal to the amino or carboxy terminus of a substrate(Ryan, 1973).