Staphylococcal lipases stereoselectively hydrolyse the sn-2 position of monomolecular films of diglyceride analogs. Application to sn-2 hydrolysis of triolein.

Using the monomolecular film technique, a kinetic study on the stereoselectivity of nine staphylococcal lipase forms was carried out with three pairs of enantiomers from diglyceride analogs (didecanoyl-deoxyamino-O-methyl glycerol, DDG) containing a single hydrolysable decanoyl ester group and two lipase-resistant groups. Our results show that the kinetic profiles of the wild type, the recombinant untagged and the recombinant tagged forms of staphylococcal lipases are significantly different. As with most of the lipases investigated so far, these staphylococcal lipases showed higher catalytic rates with primary esters than with secondary esters. However, it is noteworthy that all these staphylococcal lipases were found to significantly hydrolyse the secondary ester group of diglyceride analogs, with a strong preference for the R configuration. This stereopreference, which was predicted on the basis of Kazlauskas' rule, was comparable to that of Candida rugosa and Pseudomonas glumae lipases. As was to be expected, all the staphylococcal lipases tested efficiently hydrolysed triolein at the sn-2 position. This hydrolytic activity was quantified by performing thin-layer chromatography to analyse the hydrolytic products of triolein. From the qualitative point of view, the sn-2 preferences observed with triolein and diglyceride analogs bearing a secondary ester function were in good agreement. Diglyceride analogs might therefore provide useful initial screening tools for use in future searches for strictly sn-2 specific lipases.