Protease

Protease (also known as a proteolytic enzyme, peptidase or proteinase) is a type of enzyme that performs proteolysis, protein catabolism by hydrolysis of peptide bonds. Proteases have evolved multiple times, and different classes of protease can perform the same reaction by completely different catalytic mechanisms. Proteases can be found in all forms of life and viruses. They are involved in a multitude of physiological reactions from simple digestion of food proteins to highly regulated cascades (e.g., the blood-clotting cascade, the complement system, apoptosis pathways, and the invertebrate prophenoloxidase-activating cascade). Some viruses, such as HIV, depend on proteases in their reproductive cycle. Consequently, proteases are the target of numerous medical and agricultural research programs and are used in various industrial applications.

Classification

Proteases can be classified into seven broad groups:

1. Serine proteases
2. Threonine proteases
3. Cysteine proteases
4. Aspartic proteases
5. Metalloproteases
6. Glutamic proteases
7. Asparagine peptide lyases

The threonine and glutamic-acid proteases were not described until 1995 and 2004 respectively.

Function

Proteases are involved in digesting long protein chains into shorter fragments by splitting the peptide bonds that link amino acid residues. Some detach the terminal amino acids from the protein chain; others attack internal peptide bonds of a protein.

Medical and commercial use

Proteases are used medically and in industry. Their commercial applications include their use in detergents, food, and in the leather industry. Some proteases are considered virulence factors in some microorganisms, contributing to pathogenesis. Proteases are also used in research to remove proteins from experimental samples.

See also

• Enzyme
• Peptide bond
• Amino acid
• Serine proteases
• Threonine proteases
• Cysteine proteases
• Aspartic proteases
• Metalloproteases
• Glutamic proteases
• Asparagine peptide lyases

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