Heterologous expression, kinetic characterization and molecular modeling of a new sn-1,3-regioselective triacylglycerol lipase from Serratia sp. W3

A recombinant Serratia sp. W3 lipase (rSmL) was expressed in E. coli and purified to homogeneity. The kinetic properties, regio-selectivity, and interfacial performances of rSmL were compared with those of the native lipase (nSmL). rSmL has a molecular mass of 67 kDa and a specific activity of 3530 U mg(-1) which is around 12-fold higher than that of nSmL (300 U mg(-1)) when using olive oil as the substrate. Both rSmL and nSmL were able to hydrolyze the ester bond at the sn-1 and sn-3 positions but exhibited a clear regio-preference towards the sn-3 position of the surface-coated triglycerides (TG), which were esterified with alpha-eleostearic acid at the sn-1/3 position or dicaprin isomers spread as monomolecular films. Molecular modeling and docking of TG into the active site of rSmL indicated that this regio-preference may be due to steric hindrance, created by the residues Ile(308) and Trp(311), with distances between the sn-1 reactive carbon and the catalytic Serine residue ranging from 3.15 to 5.47 angstrom. In contrast, the sn-3 positioning within the enzyme catalytic pocket resulted in shorter distances, ranging from 2.79 to 4.15 angstrom, therefore facilitating the hydrolysis at the sn-3 position.

Automated summary

The recombinant Serratia sp. W3 lipase (rSmL) expressed in E. coli showed significantly higher specific activity compared to the native lipase (nSmL) when using olive oil as the substrate. Both rSmL and nSmL were capable of hydrolyzing ester bonds at sn-1 and sn-3 positions, however, exhibited a clear preference towards the sn-3 position of certain triglycerides due to steric hindrance within the enzyme's catalytic pocket.