A protease (additionally called a peptidase or proteinase) is an enzyme that catalyzes (increases the rate of) proteolysis, the breakdown of proteins into smaller polypeptides or unmarried amino acids. They do this by way of cleaving the peptide bonds inside proteins by means of hydrolysis, a response wherein water breaks bonds. Proteases are worried in many biological capabilities, which include digestion of ingested proteins, protein catabolism (breakdown of old proteins), and mobile signalling. Without additional supporting mechanisms, proteolysis would be very sluggish, taking masses of years. Proteases may be discovered in all kinds of life and viruses. They have independently evolved a couple of instances, and specific classes of protease can carry out the identical response through absolutely distinct catalytic mechanisms. Proteases had been first grouped into eighty four families in line with their evolutionary courting in 1993, and classified below four catalytic kinds: serine, cysteine, aspartic, and metallo proteases. The threonine and glutamic-acid proteases had been no longer described till 1995 and 2004 respectively. The mechanism used to cleave a peptide bond includes making an amino acid residue that has the cysteine and threonine (proteases) or a water molecule (aspartic acid, metallo- and acid proteases) nucleophilic so that it is able to attack the peptide carboxyl group. One way to make a nucleophile is through a catalytic triad, where a histidine residue is used to prompt serine, cysteine, or threonine as a nucleophile.