Purification and Properties of a Thermoactive Glucoamylase from Clostridium thermosaccharolyticum

Abstract

A bacterial glucoamylase was purified from the anaerobic thermophilic bacterium Clostridium thermosaccharolyticum and characterized. The enzyme, which was purified 63-fold, with a yield of 36%, consisted of a single subunit with an apparent molecular mass of 75 kDa. The purified enzyme was able to attack alpha-1,4- and alpha-1,6-glycosidic linkages in various alpha-glucans, liberating glucose with a beta-anomeric configuration. The purified glucoamylase, which was optimally active at 70 degrees C and pH 5.0, attacked preferentially polysaccharides such as starch, glycogen, amylopectin, and maltodextrin. The velocity of oligosaccharide hydrolysis decreased with a decrease in the size of the substrate. The K(m) values for starch and maltose were 18 mg/ml and 20 mM, respectively. Enzyme activity was not significantly influenced by Ca, EDTA, or alpha- or beta-cyclodextrins.