Amidases: versatile enzymes in nature.

Amidases are ubiquitous enzymes and biological functions of these enzymes vary widely. In past five decades, they turned out to be an attractive tool in industries for the synthesis of wide variety of carboxylic acids, hydroxamic acids and hydrazide, which find applications in commodity chemicals synthesis, pharmaceuticals agrochemicals and waste water treatments etc. Their proteins structures revealed that aliphatic amidases share the typical α/β hydrolase fold (like nitrilase superfamily) and signature amidases are evolutionary related to aspartic proteinases. They hydrolyse wide variety of amides (short chain aliphatic amides, mid-chain amides, arylamides, α-aminoamides and α-hydroxyamides) and can be grouped on the basis of their catalytic site and preferred substrate. They resist denaturation at extreme of pH and temperature because of their strong and compact multimeric structures. Inhibition studies and three-dimensional analysis of the structures identified a Glu59, Lys134, Cys166 catalytic triad and follow “Bi-bi Ping-Pong” mechanism reaction for amide hydrolysis and acyl transferase reactions. Many recombinant amidases have been expressed in Escherichia coli as well as in Brevibacterium lactofermentum. [ABSTRACT FROM AUTHOR]