BIOCHEMICAL-CHARACTERIZATION OF GLUCOAMYLASE FROM THE HYPERPRODUCER EXO-1 MUTANT STRAIN OF NEUROSPORA-CRASSA

The Neurospora crassa exo-l mutant produced maximum extracellular gluc oamylase activity in media supplemented with starch as the sole carbon source. The apparent molecular mass of the enzyme was 82 kDa (SDS-PAG E and gel filtration). The enzyme was a glycoprotein with 5.1% carbohy drate content and exhibited a temperature optimum of 60 degrees C. The pH optima were 5.4 and 5.0 for glucoamylase and maltase activities, r espectively. Cu2+ inhibited maltase activity while Mn2+ stimulated glu coamylase activity. The purified enzyme hydrolyzed branched substrates more efficiently than linear substrates. Starch was the best substrat e utilized and amylose was hydrolyzed faster than maltose. Kinetic exp eriments suggested that maltose and starch were hydrolyzed at the same catalytic site.