Purification and characterization of sago starch-degrading glucoamylase from Acremonium sp endophytic fungus

A novel sage starch degrading glucoamylase which had a strong amylopectin-h ydrolyzing-activity was purified to homogeneity from a culture filtrate of Acremonium sp. isolated from forest trees. The purified enzyme was an oligo meric protein of two sub-units with molecular weights of 22 and 39 kDa. Opt imum temperature and pH for enzyme activity were around 55 degrees C and 5. 5, respectively. The enzyme was stable in a pH range of 3.0-7.0 and tempera tures up to 60 degrees C. The purified enzyme was strongly inhibited by EDT A. The enzyme catalyzed hydrolysis of amylose and amylopectin, showed appar ent K-m values of 10.0 and 3.8 mg/ml and V-max of 195 mu mol/ml/min and 391 mu mol/ml/min, respectively. Glucose was the sole product released by the hydrolysis, indicating that this enzyme displays an exo-action of starch-de grading activity. (C) 2000 Elsevier Science Ltd. All rights reserved.