Evidence of Tryptophan at or near Active Site of Glucoamylase I of Arthrobotrys amerospora

Arthrobotrysamerospora (ATCC 34468) produced glucoamylase in a semi-synthetic medium containing starch as a sole carbon source. Polyacrylamide gel electrophoresis of crude glucoamylase showed three isoenzymes. They were designated as glu I, glu II and glu III according to their electrophoretic mobility. These iso-glucoamylases were purified by column chromatography using DEAE-Sephadex A-50. The major fraction, namely glu I, was subjected to various group specific reagents like NEM, idoacetamide, PALP, DEP, Rose Bengal, NBS and acarbose. N-bromosuccinimide and acarbose totally inhibited glu I. Hg2+ ion did not inhibit glu I activity at 25 m mol concentration. Glu I also showed raw starch activity.