Hydrophobic-hydrophilic interaction in lipase catalytic triad and possibility of a cofactor mediated catalysis

Lipases are ubiquitous acyl-hydrolases possessing , canonical folds within their tertiary structures. They all have SerAsp/Glu-His catalytic triad with apparently a cofactor-independent behaviour in their catalysis. The , -hydrolase lipases take part in interfacial catalysis at the lipid-water interface by extending the hydrophobic surface of the catalytic site through a peptide lid or flap. The catalytic triad, the peptide lid and an oxyanion hole together form the active site of the enzyme. The catalytic serine residue functions as a nucleophile and is deeply buried inside the -sheets and exhibits less involvement in developing the triad in the native state of the enzyme. The reversible hydrolysis-esterification reaction involves conformational changes in the protein. A peptide colipase isolated from pancreatic lipase of mammals and from birds has activating effect on the enzyme. Expression of lipA gene of Pseudomonas aeruginosa (TE3285) into E. coli host revealed the requirement for a calcium-binding protein LipB which literally serves as activator of TE3285 lipase. Calcium ion has significant role in stabilizing the ligand between the LipB and the TE3285 protein. Lipase activity is lost by scavenging action of EDTA and is regained by addition of bivalent calcium into the reaction mixture. The serine residue of lipase catalytic triad differs from that of the serine proteases to a great extent. Water molecule penetrating inside the catalytic site of lipase has limited role in charge distribution at the interface unlike phospholipases. Water once trapped within the catalytic site, is released back into a hydrophobic environment in the transition state of lipase catalysis. Lipases have wide range of industrial applications due to their regiospecificity leading to generation of minimum byproducts. Edible oils and fats can be modified by lipases for specific applications in food industry. © 2014 Universal Research Publications. All rights reserved