Insights into the molecular basis for fatty acyl specificities of lipases from Geotrichum candidum and Candida rugosa.

Despite immense progress in our comprehension of lipase structure and function during the past decade, the basis for lipase acyl specificities has remained poorly understood. This review summarizes some recent advances in the understanding at the molecular-level of substrate acyl recognition by two members in a group of large (Mw approximately 60 kDa) microbial lipases. Two aspects of acyl specificity will be focused upon. (i) The unique preference of a fungal Geotrichum candidum lipase for long-chain cis (delta-9) unsaturated fatty acid moieties in the substrate. Mutational analysis of this lipase identified residues essential for its anomalous acyl preference. This information highlighted for the first time parts in the lipase molecule involved in substrate acyl differentiation. These results are discussed in the context of the 3D-structure of a G. candidum lipase isoenzyme and structures of the related Candida rugosa lipase in complex with inhibitors. (ii) The mechanism by which the yeast C. rugosa lipase discriminates between enantiomers of a substrate with a chiral acyl moiety. Molecular modeling in combination with substrate engineering and kinetic analyses, identified two alternative substrate binding models. This allowed for the proposal of a molecular mechanism explaining how long-chain alcohols can act as enantioselective inhibitors of this enzyme. A picture is thus beginning to emerge of the interplay between lipase structure and fatty acyl specificity.