Kinetic Study on Maltal Binding Site of Sweet Potato β-Amylase

Abstract

Sweet potato β-amylase catalyzes two different kinds of reactions:hydrolysis of amylose, etc. and hydration of maltal (α-D-glucopyranosyl-(1→4)-2-deoxy-D-glucal). To investigate whether both the reactions are catalyzed at the same catalytic site or not, an inhibition study on both the reactions and an affinity-labeling of Glu187 were done using 4-O-α-D-glucopyranosyl-(1→4)-1-deoxy-nojirimycin (GDN) as an inhibitor. As GDN showed competitive inhibition with the same K_i for these reactions, it was concluded that both the reactions occur at the same catalytic site.