ABSTRACT
An amylase was purified from the culture filtrate of Termitomyces clypeatus by ammonium sulphate precipitation, DEAE-Sephadex chromatography and gel filtration on Bio-Gel P-200 column. The electrophoretically homogeneous preparation also exhibited hydrolytic activity (in a decreasing order) on amylose, xylan, amylopectin, glycogen, arabinogalactan and arabinoxylan. The enzyme had characteristically endo-hydrolytic activity on all the substrates tested and no xylose, glucose, arabinose or glucuronic acid could be detected even after prolonged enzymatic digestion of the polysaccharides. Interestingly the enzyme had similar pH optima (5·5), temperature optima (55°C), pH stability (pH 3-10) and thermal denaturation kinetics when acted on both starch and xylan (larch wood). Km values were found to be 2·63 mg/ml for amylase and 6·25 mg/ml for xylanase activity. Hill's plot also indicated that the enzyme contained a single active site for both activities. Hg2+ was found to be most potent inhibitor. Ca2+ , a common activator for amylase activity, appeared to be an inhibitor for this enzyme. Thus it appeared that the enzyme had multisubstrate specificity acting as α-amylase on starch and also acting as xylanase on side chain oligosaccharides of xylan containing α-linked sugars.