CELLULASE (BETA-I,4-GLUCAN 4-GLUCANOHYDROLASE) FROM WOOD-DEGRADING FUNGUS POLYPORUS SCHWEINITZII FR .2. CHARACTERIZATION

1. 1. Some properties of an endocellulase (β-1,4-glucan 4-glucanohydrolase, EC 3.2.1.4), previously isolated from culture filtrates of the wood degrading fungus Polyporus schweinitzii Fr. have been investigated. 2. 2. The cellulase is stable between pH 2.6 and 7.5. Using a viscosimetric test with CM-cellulose as the substrate, an optimum activity was found at about pH 4.0, although only a very slight fall was observed at a lower pH. With an increasing pH above 4.0, the activity decreased sharply, and the enzyme is almost inactive above pH 6.0. 3. 3. The cellulase has an optimum activity at about 60° and is almost completely stable up to this temperature; at higher temperatures it is rapidly denatured. 4. 4. The molecular weight was determined on a calibrated Sephadex G-100 column and was found to be 45 000 ± 4 500. 5. 5. Dewaxed cotton cellulose is practically unattacked by the cellulase both before and after purification and after the addition of a mycelium extract, whereas a regenerated cellulose was readily degraded; the amorphous regions are preferentially attacked. 6. 6. It was found that hydroxyethylcellulose was more easily degraded than a CM cellulose with a similar degree of substitution and, in limited experiments with hydroxyethylcelluloses, that susceptibility to enzymatic attack is inversely proportional to the degree of substitution. 7. 7. The results are compared with those for cellulases from other sources and are discussed in relation to the behavior of P. schweinitzii in vivo. © 1969.