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The secretion of 1,4-beta-D-glucanases by the basidiomycete Schizophyllum commune in response to cellulose or cellobiose has been studied. The proteins were labeled with 35S, and the secretion of enzymes was measured by beta-glucosidase and carboxymethyl cellulase activities and by immunoprecipitation with specific antibodies. The antigen proteins used were a beta-glucosidase (Mr, 93,000), an avicelase (avicelase II; Mr, 64,000), and a carboxymethyl cellulose (carboxymethyl cellulase I; Mr 41,000). The beta-glucosidase was initially secreted as an Mr 110,000 form, which was followed later by lower-molecular-weight (88,000 to 93,000) forms. The avicelase II, which accounted for about 50% of the secreted labeled protein, had an Mr of 64,000. Secretion of the related avicelase I (Mr 61,000) followed later. The carboxymethyl cellulose I was secreted in two molecular weight forms, Mr 44,000 and 41,000. The evidence is consistent with the idea that three genes account for the secreted glucanase activities. Other species result from different glycosylation or proteolytic cleavage processing, which may occur during or after secretion. The beta-glucosidase secretion appears to be regulated differently than that of avicelase II or carboxymethyl cellulase I; the latter two were regulated coordinately under the conditions used in this work. No common immune determinants between the three antigens were observed.

Several mono-, di, tetra-, and polysaccharides were screened for their ability to induced cellulase production by the tetrapolar hymenomycete Schizophyllum commune. Out of 21 carbohydrates screened, 4 (thiocellobiose, carboxymethylcellulose, cellobiose, and xylan) induced all three enzymes tested (carboxymethylcellulase, beta-glucosidase, and xylanase). The inducing effect increased with rising concentrations of the inducers up to a certain value, beyond which there was either a leveling off or a decrease of the enzymatic activities. The most powerful inducer, thiocellobiose, showed the highest activity at 0.5 mM. Cellobiose, carboxymethylcellulose, and xylan showed their highest activities at 1 mM and 1%, respectively. Surprisingly, sophorose did not enhance enzyme production. The enzymatic activities were monitored over a period of 24 h. Thiocelloboise elicited a response immediately after incubation, but with all other inducers there was a latency period before their effect could be measured. High-performance liquid chromatography showed no hydrolysis of thiocellobiose when incubated in the presence of S. commune extracellular enzymes.