PURIFICATION AND CHARACTERIZATION OF 4 EXTRACELLULAR 1,3-BETA-GLUCANASES OF BOTRYTIS-CINEREA

The filamentous fungus Botrytis cinerea was found to produce four 1,3-beta-glucanases (Glu I, II, III, IV). These enzymes were visualized by activity-staining after separation by native polyacrylamide get electrophoresis (PAGE). During growth on glucose as the single carbon source, only Glu III was detectable in the culture supernatant of B. cinerea. After glucose was exhausted from the medium, the extracellular (1,3)(1,6)-beta-D-glucan (cinerean) capsule of the fungus was degraded. In this phase the other three enzymes became detectable and the amount of all four enzymes increased. The enzyme with the greatest activity was Glu II, which was purified to homogeneity by SDS-PAGE. Its M(r) was 75000 and its isoelectric point (pI) was 5-2. Glycosylation of Glu II was shown by the periodic acid/Schiff reaction after SDS-PAGE. Glu II cleaved cinerean and laminarin. Both substrates were degraded in an exo-manner as shown by product characterization, and by studying the viscosity decrease in comparison with the liberation of reducing groups. The concentration of substrate that gave half-maximal velocity (S0.5) for Glu II was 580 mug ml-1 for cinerean and 152 mug ml-1 for laminarin. For Glu III, also purified to homogeneity by SDS-PAGE, an M(r) of 84000 and a pl of 3.6 were determined. Glu III cleaved laminarin (S0.5 119 mug ml-1) but not cinerean. Glu I and Glu IV were purified by activity-stained native PAGE. Both enzymes cleaved cinerean and laminarin in an exo-manner. Glu I focused at pl 4.9; its S0.5 was 275 mug ml-1 with cinerean and 138 mug ml-1 with laminarin. The pI of Glu IV was 3.4; its S0.5 was 171 mug ml-1 for cinerean and 27 mug ml-1 for laminarin.