Differential Assay of Human Pancreatic and Salivaryα-Amylases withp-Nitrophenyl 65-O-β-D-Galacopyraosyl-α-maltopentaoside as the Substrate

Abstract

p-Nitrophenyl 65-O-β-D-galactopyraosyl-α-maltopentaoside (L6G5P) was synthesized by the sequential use of the transglycosylation and hydrolytic action of β-D-galactosidase from Bacillus circulans. The enzyme produced L6G5P (at a yield of 8.0% based on the amount of p-nitrophenyl α-maltopentaoside added) from lactose as the donor and p-nitrophenyl α-maltopentaoside as the acceptor. The frequency at which of human pancreatic α-amylase and salivary α-amylase catalyzed the cleavage of glycosidic linkages in L6G5P was calculated by analysis of the digests by high-pressure liquid chromatography. The modes of action of the two isozymes differed. Both hydrolyzed L6G5P and produced p-nitrophenyl α-maltoside and p-nitrophenyl α-D-glucopyranoside, but human pancreatic α-amylase produced more of the latter than human salivary α-amylase. Thus, L6G5P could be used to assay of the two enzymes differentially in serum.