Purification and Characterization of an Amyloglucosidase from <i>Termitomyces clypeatus</i> That Liberates Glucose From Xylan

Abstract

Abstract An amyloglucosidase was purified to homogeneity from the culture filtrate of Termitomyces clypeatus , using the following steps: ammonium sulfate fractionation, DEAE‐Sephadex chromatography, and HP‐GPLC on an Ulstropac TSK‐G3000 SWG column. The enzyme was a glycoprotein with a minimum molecular weight of 56 000. It had appreciable activity on glycogen and amylopectin, moderate activity on maltose, and little activity on panose. The enzyme, unlike fungal amyloglucosidase ( Aspergillus niger ), could liberate glucose from xylans. The enzyme had K m = 1.81 mg/mL and V m = 82.1 μ mol/min/mg for starch hydrolysis and K m = 4.36 mg/mL and V m = 57.7 μ mol/min/mg for the hydrolysis of larch wood xylan. Among the different inhibitors, NBS and CDTA were the most potent. Previously the enzyme was shown [Khowala, S.; et al . Appl. Microbiol. Technol . 1992 , 37 , 287–292] to have synergistic activity on xylan hydrolysis similar to other xylanolytic enzymes: α‐arabinofuranosidase or α ‐glucuronidase. Since the amyloglucosidase was not active on cellulose, arabinogalactan, or β‐glucans, which may be present as contaminants in xylan, the probable liberation of glucose directly from xylan by the enzyme was indicated.