Microbial lipases

Lipases (triacylglycerol acylhydrolases, EC 3.1.1.3) are enzymes that catalyze the reversible hydrolysis of triacylglycerols (TAGs) under natural conditions. Widely distributed in animals, plants, and microbes, lipases differ from other esterases and are unique in that their activity is greatest against water-insoluble substrates and is enhanced at the substrate (oil)-water interface; that is, they exhibit “interfacial activation.” Optimum activities are obtained in systems such as emulsions, where high surface areas of the substrate can be obtained. Lipases are active not only in normal-phase emulsions where the substrate is emulsified into an aqueous system (oil-in-water) but also, often more active, in invert (waterin- oil) emulsions and in reverse micelle systems containing an organic solvent solution of the substrate. Furthermore, lipases are exceedingly versatile in that they can also catalyze transesterification reactions and the stereospecific synthesis of esters, and they can act on a broad range of substrates. Major advances have been made in our understanding of lipolytic enzymes over the past few years through solving the crystal structures of lipases from several sources. Knowledge of their structures has given insight into the mechanism of action, interfacial activation, specificity, and the nature of the active site. The high current interest in lipases, shown by the large volume of recent scientific literature on the topic, is driven by the great potential in a diversity of commercial applications for these enzymes. This chapter gives an overview of lipases and their properties, with a focus on the topics of current research interest such as lipase structure and its implications in interfacial activation and selectivity. The emphasis is on microbial lipases, particularly from fungi, with references to human pancreatic lipase for comparison.