Structural investigations of the regio- and enantioselectivity of lipases

Abstract

Although lipases are widely applied for the stereospecific resolution of racemic mixtures of esters, the atomic details of the factors that are responsible for their stereospecificity are largely obscure. We determined the X-ray structures of Pseudomonas cepacia lipase in complex with two enantiopure triglyceride analogues, that closely mimic natural substrates. This allowed an unambiguous view of how the two wings of the boomerang-shaped active site accommodate the acyl and alcohol parts of the triglyceride. The binding groove for the hydrophobic sn-3 fatty acid chain is large and hydrophobic. The cleft for the alcohol moiety is divided in two parts, one tightly binding the sn-2 acyl chain with hydrophilic and hydrophobic interactions, the other more weakly binding the sn-1 fatty acid. The enantioselectivity of Pseudomonas cepacia lipase seems therefore to be predominantly determined by the size and interactions of the sn-2 chain and by the size of the sn-3 chain.