2 KINDS OF NOVEL ALPHA-GLUCOSIDASES FROM ASPERGILLUS-AWAMORI KT-11 - THEIR PURIFICATIONS, PROPERTIES AND SPECIFICITIES

Two glucose-forming enzymes were purified to an electrophoretically pu re state from the extract of koji culture of Aspergillus awamori KT-11 using wheat bran. Both the enzymes hydrolyzed maltotriitol to produce an alpha-anomeric form of glucose and maltitol, and were identified a s alpha-glucosidases (named alpha-G I and alpha-G II). The molecular w eights were determined to be 108,000 for alpha-G I and 106,000 for alp ha-G II by fast protein liquid chromatography, but their amino acid co mpositions were almost the same. The molecular weights of the subunits were estimated by sodium dodecyl sulfate-polyacrylamide gel electroph oresis (SDS-PAGE) to be 62,000 and 31,000 for the former and 59,000 an d 31,000 for the latter. The optimum pH for bath enzymes was 5.2. The action pattern of these enzymes was almost the same, namely, hydrolysi s of maltotetraose, isopanose, maltotriose, maltotriitol, panose, malt opentaose, maltose, maltohexaose, isomaltose, maltoheptaose in order o f the initial reaction velocity, and their action was very weak on nig erose, maltitol and amylose to produce only glucose on a relatively lo w concentration of the substrates. However, neither acted on trehalose and sucrose. On the other hand, both strongly catalyzed the transfer action of a dense concentration of maltose to produce isomaltose, pano se and other maltooligosaccharides with higher molecular weights than panose. The best conditions for the production of panose by the transf er action of alpha-G I were at pH 6.7 (yield, 31.0%), temperature 27 d egrees C (yield, 34.3%) and 60% (w/v) of substrate concentration (yiel d 32.5%). From the results, both alpha-G I and alpha-G II were conclud ed to be novel enzymes.