Institution: | a ENSSPICAM, UMR 6516, “Synthèse, Catalyse et Chiralité”, avenue Escadrille Normandie-Niemen, F-13397 Marseille, Cedex 20, France b Laboratoire de Lipolyse Enzymatique, UPR 9025, IFR 1 du CNRS, 31, Chemin Joseph Aiguier, F-13402 Marseille, Cedex 20, France |
Abstract: | Enantiomerically pure alkylphosphonate compounds RR′P(O)PNP (R=CnH2n+1, R′=OY with Y=Cn′H2n′+1 with n=n′ or n≠n′; PNP=p-nitrophenoxy) noted (RY), mimicking the transition state occurring during the carboxyester hydrolysis were synthesized and investigated as potential inhibitors of human gastric lipase (HGL) and human pancreatic lipase (HPL). The inhibitory properties of each enantiomer have been tested with the monomolecular films technique in addition to an enyzme linked immunosorbent assay (ELISA) in order to estimate simultaneously the residual enzymatic activity as well as the interfacial lipase binding. With both lipases, no obvious correlation between the inhibitor molar fraction (50) leading to half inhibition, and the chain length, R or Y was observed. (R11Y16)s were the best inhibitor of HPL and (R10Y11)s were the best inhibitors of HGL. We observed a highly enantioselective discrimination, both with the pure enantiomeric alkylphosphonate inhibitors as well as a scalemic mixture. We also showed, for the first time, that this enantioselective recognition can occur either during the catalytic step or during the initial interfacial adsorption step of the lipases. These experimental results were analyzed with two kinetic models of covalent as well as pseudo-competitive inhibition of lipolytic enzymes by two enantiomeric inhibitors. |