Kinetic study on maltal binding site of sweet potato β-amylase

Sweet potato β -amylase catalyzes two different kinds of reactions: hydrolysis of amylose, etc. and hydration of maltal (α-D-gluco- pyranosyl-(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 Glul87 were done using 4-O- α -D-glucopyranosyl-(1→4)-l-deoxy- nojirimycin (GDN) as an inhibitor. As GDN showed competitive inhibition with the same Ki for these reactions, it was concluded that both the reactions occur at the same catalytic site.