Protein hydrolyzing enzymes are known as protease. About.com Chemistry specifically defines protease as an enzyme that initiates the hydrolysis of a peptide bond to form polypeptide chains. A protease is also known as a peptidase or proteinase.
Occurring naturally in all organisms, proteases are involved in physiological reactions. They aid in simple digestion of food proteins and create blood-clotting cascades and apoptosis pathways. Proteases can break individual peptide bonds or a complete peptide down to amino acids.
Proteases are classified into groups: serine, threonine, cysteine, aspartic acid, glutamic acid and metalloproteases. Threonine was not chronicled until 1995. Glutamic acid was not specified until 2004.