Enzymatic Synthesis of p-Nitrophenyl α-Maltoheptaoside by Transglycosylation of Maltohexaose-forming Amylase

An extracellular maltohexaose-forming amylase [EC 3.2.1.98] from Klebsiella pneumoniae mutant is a normal hydrolytic enzyme that hydrolyzes short-chain amylose to give about 40 % maltohexaose. Transglycosylation from maltoheptaose to the 4-position of p-nitrophenyl α-glucoside was efficiently induced through the use of maltohexaose-forming amylase in an aqueous methanol solution. The enzyme specifically produced p-nitrophenyl α-maltoheptaoside (13 % of the p-nitrophenyl α-glucoside) from maltoheptaose as a donor and p-nitrophenyl α-glucoside as an acceptor. The yield of p-nitrophenyl α-maltoheptaoside depended on the concentration of methanol solvent, the pH, and temperature. Furthermore, the use of the aqueous methanol system in the reaction not only improved the solubility of p-nitrophenyl α-glucoside but also greatly increased the formation of p-nitrophenyl α-maltoheptaoside, which is a useful substrate for assay of human amylase in serum and urine.