Purification and characterization of a new type of α-glucosidase from Paecilomyces lilacinus that has transglucosylation activity to produce α-1,3- and α-1,2-linked oligosaccharides

A fungus producing an α-glucosidase that synthesizes α-1,3- and α-1,2-linked glucooligosaccharides by transglucosylation was isolated and identified as Paecilomyces lilacinus. The cell-bound enzyme responsible for the synthesis was extracted by suspension of mycelia with 0.1 M phosphate buffer (pH 8.0), and the extract was purified. The molecular weight and the isoelectric point were estimated to be 54,000 and 9.1, respectively. The enzyme was most active at pH 5.0 and 65°C. The enzyme hydrolyzed maltose, nigerose, and kojibiose. The enzyme also hydrolyzed soluble starch and amylose with the rate toward maltose. p-Nitrophenyl α-glucoside and isomaltose were not good substrates. The enzyme had high transglucosylation activity to synthesize oligosaccharides containing α-1,3- and α-1,2-linkages. At an early stage of the reaction, considerable maltotriose, 4-O-α-nigerosyl-D-glucose, and 4-O-α-kojibiosyl-n-glucose were synthesized. Afterwards, nigerose and kojibiose were accumulated gradually with glucose as an acceptor.