Enzymatic synthesis of Acarviosyl-maltooligosaccharides using disproportionating enzyme 1

Acarbose is a pseudo-tetrasaccharide and one of the most effective inhibitors of glycoside hydrolases. Its derivatives, acarviosyl-maltooligosaccharides, which have longer maltooligosaccharide parts than the maltose unit of acarbose, were synthesized using a disproportionating enzyme partially purified from adzuki cotyledons. The enzyme was identified as a typical type-1 disproportionating enzyme (DPE1) by primary structure analysis. It produced six compounds from 100 mM acarbose and 7.5% (w/v) of maltotetraose-rich syrup. The masses of the six products were confirmed to accord with acarviosyl-maltooligosaccharides with the degrees of polymerization = 5-10 (AC5-AC10) by electrospray ionization mass spectrometry. (1)H and (13)C NMR spectra indicated that AC5-AC10 were α-acarviosyl-(1→4)-maltooligosaccharide, which have maltotriose-maltooctaose respectively in the maltooligosaccharide part. A predominance of AC7 in the products at the early stage of the reaction indicated that DPE1 catalyzes the transfer of the acarviosyl-glucose moiety from acarbose to the acceptors. ACn can be useful tools as new inhibitors of glycoside hydrolases.