Protease

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A protease (also termed peptidase or proteinase) breaks down proteins. A protease is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein.

Contents

Classification

Standard

Proteases are currently classified into six broad groups:

The threonine and glutamic-acid proteases were not described until 1995 and 2004, respectively. The mechanism used to cleave a peptide bond involves making an amino acid residue that has the cysteine and threonine (proteases) or a water molecule (aspartic acid, metallo- and glutamic acid proteases) nucleophilic so that it can attack the peptide carboxyl group. One way to make a nucleophile is by a catalytic triad, where a histidine residue is used to activate serine, cysteine, or threonine as a nucleophile.

Within each of the broad groups proteases have been classified, by Rawlings and Barrett, into families of related proteases. For example within the Serine proteases families are labelled Sx where S denotes the serine catalytic type and the x denotes the number of the family, for example S1 (chymotrypsins). An up to date classification of proteases into families is found in the MEROPS database .[1] [2].

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