Extreme Environments: Goldmine of Industrially Valuable Alkali-stable Proteases

Proteases are a complex group of enzymes which have immense physiological as well as commercial importance as they possess both degradative and synthetic properties. They differ substantially in their origin, catalytic mechanism, substrate specificity and active site. Proteases are broadly divided as exopeptidases and endopeptidases depending on their sites of action. If the enzyme cleaves the peptide bond proximal to the amino or carboxy terminus of the substrate, they are classified as exopeptidases. If the enzyme cleaves peptide bonds distant from the terminus of a substrate, they are classified as endopeptidases. Further, on the basis of functional group(s) present at the active site and enzymes’ catalytic mechanism, proteases are categorized into four groups: serine-, cysteine-, asparticand metalloproteases. Proteases are universally present in animals, plants and microorganisms. However, microbes are a goldmine of proteases and represent the preferred source of enzymes [1].