The Inhibitory Effect of Propranolol and Isoproterenol on Human Plasma Cholinesterase

Abstract

The effect of propranolol and isoproterenol on the hydrolysis of 4- nitrophenylbutyrate (PNPB) by the purified human plasma cholinesterase was studied. During the hydrolysis of PNPB, enzyme obeyed to Michaelis-Menten model. Propranolol was found to be a competitive inhibitor, and isoproterenol yielded a complex inhibition pattern. It could be explained that the inhibitory effect of propranolol shows noncooperativity between subunits of human plasma cholinesterase upon binding of PNPB. In contrast, isoproternol inhibitory effects indicate more than one type of binding sites on this enzyme.