Location and kinetic properties of the cellulase system of Acetivibrio cellulolyticus

Abstract

The cellulose-solubilizing and carboxymethylcellulase activities of Acetivibrio cellulolyticus were observed to exist largely in a soluble form whereas β-glucosidase activity was cell associated. Reducing agents significantly enhanced cellulose-solubilizing activity, and thiol-binding agents at micromolar concentrations resulted in almost total inhibition of this activity. Carboxymethylcellulase activity was also inhibited by these agents but to a lesser degree. Cellulose-solubilizing activity was strongly stimulated by Mg²⁺ and Ca²⁺ but these ions had a negligible effect on carboxymethylcellulase activity. Cellulase activity was not inhibited by glucose and only slightly by cellobiose. A strong preference for p-nitrophenylglucoside over cellobiose by β-glucosidase activity was observed.