Enzyme inhibition by p-cresol and lacticacid in lipase-mediated synthesis of p-cresyl acetate and stearoyl lactic acid: a kinetic study

Abstract

A detailed kinetic study was carried out to investigate the porcine pancreatic lipase-catalysed esterification reactions of p-cresol–acetic acid and lactic acid–stearic acid. The kinetic data were in agreement with a Ping Pong Bi–Bi mechanism being followed by the enzyme, where inhibition is indicated in the presence of p-cresol and lactic acid in the respective reactions. Mathematical analyses of experimentally observed initial rates yielded various kinetic parameters, K m(p-cresol) = 0.1, K m(acetic acid) = 0.54, K m(lactic acid) = 0.059 M, K m(stearic acid) = 0.04 M, V max(p-cresol–acetic acid) = 13.2(h−1), V max(lactic acid–stearic acid) = 0.00163 M/h, K i(p-cresol) = 0.59 and K i(lactic acid) = 0.079 M. The K m and K i values of p-cresol and lactic acid observed in the respective reactions showed both the competitive nature of binding between the substrates p-cresol and acetic acid on the one hand and lactic acid and stearic acid on the other and the inhibitory nature of p-cresol and lactic acid.