The substrate specificity and mode of action of the four pure P-D-glucosidase enzymes (EC 3.2.1.21) from Sclerotium rolfiii were studied and their contribution to cellulolysis is discussed. The enzymes are specific for substrates having the p-D configuration.
The specificity of the enzymes is not restricted to the p-~-(1-+4) linkage, as all four P-D-glucosidases hydrolyzed substrates having p-~-(1+6)-, (l-3) and -(l-+2) linkages. The enzymes require strictly a D-gluco configuration for activity. The /!?-D-glucosidases had no action on highly ordered cellulose, such as Avicel, but slowly hydrolyzed disordered cellulose (phosphoric acid-swollen Avicel) and carboxymethylcellulose, and rapidly cellodextrins, removing D-ghCOSe residues from the nonreducing end. The pure enzymes behaved rather as exo-p-Dglucan glucohydrolase.
The K,,, values of all four P-D-glucosidases decreased with increase in the chain length of cellodextrins.
Cellopentaose was the preferred substrate for all four enzymes. The major route of D-ghCOSe formation from cellulose by hydrolysis with S. rolfsii /3-D-glucosidases proceeds through higher-molecularweight cellodextrins.
*NCL Communication
No. 2730.