Clarification of Hydrolysis of An Ester on LipA: (2)Reaction Analysis Based on FMO and MOPAC PM6 methods

Abstract

Lipase A from Bacillus subtilis 168 (LipA) shows enantioselectivity on ester hydrolysis reactions producing (R)-IPG (1,2-O-isopropylidene-sn-glycerol) more than (S)-IPG from the racemate. In order to investigate the reaction mechanism, we estimated interaction energy between residues in LipA and the substrate-Ser77 complex by using Gamess/FMO method. Then, selecting five residues playing important role on the hydrolysis reaction, the energies of three states of Michaelis Complexes (MC), Transition States (TS), and Tetrahedral Intermediates (TI) for two crystals of 1R50 (producing (R)-IPG) and 1R4Z (producing (S)-IPG) were calculated with MOPAC PM6. The initial stage of the possible hydrolysis mechanism has become to be clarified qualitatively.