PRODUCTION, PURIFICATION, AND CHARACTERIZATION OF AN EXTRACELLULAR ENDO-BETA-1,3-GLUCANASE FROM A MONOKARYON OF SCHIZOPHYLLUM-COMMUNE ATCC-38548 DEFECTIVE IN EXO-BETA-1,3-GLUCANASE FORMATION

Production of extracellular beta-1,3-glucanase activity by a monokaryo tic Schizophyllum commune strain was monitored and results indicated t hat the beta-glucanase activity consisted of an endo-beta-1,3-glucanas e activity, besides a negligible amount of beta-1,6-glucanase and beta -glucosidase activity. Unlike the beta-1,3-glucanase production of the dikaryotic parent strain S. commune ATCC 38548, the beta-1,3-glucanas e formation of the monokaryon was not regulated by catabolite repressi on. The endo-beta-1,3-glucanase of the monokaryon was purified from th e culture filtrate by lyophilization, anion exchange chromatography on Mono Q, and gel filtration on Sephacryl S-100. It appeared homogeneou s on SDS-PAGE with a molecular mass of 35.5 kDa and the isoelectric po int was 3.95. The enzyme was only active toward glucans containing bet a-1,3-linkages, including lichenan, a beta-1,3-1,4-D-glucan. It attack ed laminarin in an endo-like fashion to form laminaribiose, laminaritr iose, and high oligosaccharides. While the extracellular beta-glucanas es from the dikaryotic S. commune ATCC 38548 degraded significant amou nts of schizophyllan, the endo-beta-1,3-glucanase from the monokaryon showed greatly reduced activity toward this high molecular mass beta-1 ,3-/beta-1,6-glucan. The K-m of the endoglucanase, using laminarin as substrate, was 0.28 mg/mL. Optimal pH and temperature were 5.5 and 50 degrees C, respectively. The enzyme was stable between pH 5.5 and 7.0 and at temperatures below 50 degrees C. The enzyme was completely inhi bited by 1 mM Hg2+. Growth of the monokaryotic S. commune strain was n ot affected by its constitutive endo-beta-1,3-glucanase formation.