Molecular basis of lipase stereoselectivity

Abstract

Lipases exhibit specific catalytic properties that make them attractive to biotechnological applications. Most important are the broad substrate specificity and the regio- and stereoselectivity of lipases. Despite mechanistic and structural similarities lipases differ significantly with respect to stereoselectivity toward natural and synthetic substrates. Models developed to describe and predict stereoselectivity toward certain types of synthetic substrates, e. g., secondary alcohols cannot be applied to natural acylglycerols, that are hydrolyzed by several animal and microbial lipases in a regioselective or stereoselective manner. Therefore, computer-aided molecular modeling studies were used in order to predict the stereopreference of lipases toward triradylglycerols. Lipase variants with modified stereoselectivity properties toward triacylglycerols were engineered by re-designing the recombinant enzyme. To understand the interactions governing lipase stereoselectivity towards natural substrates, knowledge of the structure of enzyme-substrate complexes at the atomic level is essential. Such information can be obtained by X-ray or NMR analysis of covalent enzyme-inhibitor complexes. The crystal structures of enzymes complexed with triacylglycerol analog inhibitors allowed the identification of distinct binding sites for the three hydrophobic chains of the inhibitor.