The inhibition of β‐glucosidase activity in <i>Trichoderma reesei</i> C30 cellulase by derivatives and isomers of glucose

Abstract

Abstract The inhibition of β‐glucosidase in Trichoderma reesei C30 cellulase by D ‐glucose, its isomers, and derivatives was studied using cellobiose and ρ‐nitrophenyl‐β‐glucoside (PNPG) as substrates for determining enzyme activity. The enzymatic hydrolysis of both substrates was inhibited competitively by glucose with approximate K i values of 0.5m M and 8.7m M for cellobiose and PNPG as substrate, respectively. This inhibition by glucose was maximal at pH 4.8, and no inhibition was observed at pH 6.5 and above. The α anomer of glucose inhibited β‐glucosidase to a greater extent than did the β form. Compared with D ‐glucose, L ‐glucose, D ‐glucose‐6‐phosphate, and D ‐glucose‐1‐phosphate inhibited the enzyme to a much lesser extent, unlike D ‐glucose‐ L ‐cysteine which was almost as inhibitory as glucose itself when cellobiose was used as substrate. Fructose (2−100m M ) was found to be a poor inhibitor of the enzyme. It is suggested that high rates of cellobiose hydrolysis catalyzed by β‐glucosidase may be prolonged by converting the reaction product glucose to fructose using a suitable preparation of glucose isomerase.