Proteases: Introduction and Application
Author: Sumit Kumar Dubey

Enzymes are efficient catalysts to speed up biochemical reactions at ambient conditions by lowering the activation energy. Enzymes are classified into six groups namely oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases. Among different groups, the hydrolase enzymes e.g. protease, amylase, lipase and cellulase are extensively studied due to their wide variety of application in food processing, pharmaceuticals, detergents additives, waste treatment, animal feed additives, digestive supplements, bio-energy (bio-fuel and bio-gas), bioremediation, textile and beverages.

Present article deals with the proteases enzyme that performs proteolysis. Proteases (proteolytic enzymes) could be produced/or recovered by plants, animals and microbes (e.g. bacteria, fungi and viruses). Various literatures support the fact that microorganisms are an excellent source of protease production at commercial scale. A large number of microbes belonging to bacteria and fungi are known to produce significant amount of proteases via fermentation. Serine proteases usually produced by microorganisms belonging to the Bacillus sp., Aspergillus sp. and Streptomyces sp. Microbial proteases account for 40% (approx) of the total worldwide sales of industrial enzymes. Alkaline proteases are more preferable for industrial purpose as compared to acidic proteases. Alkaline protease has wide applications in detergent formulations. Usually microbial strains produce extracellular proteases that could easily be recovered from the fermentation broth.

There are various types of classification of proteases has been published.

  • On the basis of pH – acidic protease, neutral protease and alkaline protease.
  • On the basis of peptide bond specificity endo- peptidases and exo- peptidases.
  • On the basis of functional group at active site – serine protease, cysteine protease, aspartic protease and metallo-proteases.

    Two mechanism of action of proteases have been reported. First mechanism depends on nucleophilic attack on the peptide bond. Aspartic, glutamic and metallo- proteases activate a water molecule which performs a nucleophilic attack on the peptide bond to hydrolyze it. Second mechanism is based on the action of catalytic triad (nucleophilic residue) that performs a nucleophilic attack to covalently link the protease to the substrate protein, releasing, the first half of the product. This covalent acylenzyme intermediate is then hydrolysed by activated water to complete catalysis by releasing the second half of the product and regenerating the free enzyme.

    The protease inhibitor is also plays important role in molecular biology e.g. tumor protease inhibitor could be used to suppress tumor. Protease inhibitor could be used in antiretroviral therapy, especially against HIV which depends on proteases for reproductive cycle.

    Possible research area for new researcher –

About Author / Additional Info:
Faculty, Department of Biotechnology, D.L.S. PG. College, Bilaspur 495001, India