Inhibition of reduced DP18-maltodextrin and amylose hydrolysis by acarbose: kinetic studies

Abstract

Kinetics of inhibition of porcine pancreatic alpha-amylase by acarbose were performed using maltodextrin and amylose as substrates. Similar Lineweaver-Burk primary plots were obtained. Two mixed non-competitive models are proposed. X-ray crystallographic data (Qian, M., Buisson, G., Duée, E., Haser, R. and Payan, F. Biochemistry, 1994; 33: 6284-6294) are in support of the mixed non-competitive inhibition model which involves abortive complexes. Secondary plots are different indicating that in the maltodextrin hydrolysis, one molecule of acarbose is bound per amylase molecule, while using amylose as substrate two molecules of acarbose are bound. These two kinetically determined binding sites might correspond to the two surface sites shown by X-ray crystallography (Qian, M., Haser, R. and Payan, F. Protein Science 1995; 4: 747-755).