Formation of 6-O-alpha-maltosylcyclomalto-oligosaccharides by transfer action of three debranching enzymes.
O-Maltosylcyclomaltohexaoses (G2-cG6) were formed in yields of 24.3 and 23.2 mmol from 40 mmol of alpha-maltosyl fluoride (alpha-G2F) and 90 mmol of cyclomaltohexaose (cG6) by the transfer action of pullulanase from Aerobacter aerogenes (A-pullulanase) and isoamylase from Pseudomonas amyloderamosa, respectively. These yields were three times that given by pullulanase from Bacillus acidopullulyticus (B-pullulanase). The yields of O-maltosylcyclomalto-oligosaccharides were changed according to the origin of the enzymes and the kind of cyclomalto-oligosaccharide (cG6, cG7, or cG8) used as the acceptor. By the reaction with 40 mmol of alpha-G2F and 90 mmol of cG6, 20 mmol of alpha-G2F and 30 mmol of cG7, or 40 mmol of alpha-G2F and 90 mmol of cG8, the amounts of O-maltosylcyclomalto-oligosaccharides produced and the transfer ratios of alpha-G2F to the acceptors were as follows. By A-pullulanase, 24.3 mmol of G2-cG6 was produced in a 60.8% transfer ratio, whereas the yields of G2-cG7 and G2-cG8 were 1.7 mmol (8.5%) and 8.4 mmol (21.0%), respectively. The yields of G2-cG6, G2-cG7, and G2-cG8 by B-pullulanase were 8.8 mmol (22.0%), 1.2 mmol (6.0%), and 11.7 mmol (29.3%), respectively. In the case of isoamylase, G2-cG7 (9.2 mmol, 46.0%) and G2-cG8 (20.9 mmol, 52.3%) were produced, as much as for G2-cG6 (23.2 mmol, 58.0%). It was suggested that the difference in the amounts of G2-cG6 produced by these three debranching enzymes is based on the difference in the mode of action on the alpha-G2F used as the substrate, either a transfer action or a hydrolytic action.