Some kinetic properties of the β- -glucosidase (cellobiase) in a commercial cellulase product from Penicillium funiculosum and its relevance in the hydrolysis of cellulose

Some kinetic parameters of the β- -glucosidase (cellobiase, β- -glucoside glucohydrolase, EC 3.2.1.21) component of Sturge Enzymes CP cellulase see 1,4-(1,3;1,4)-β- -glucan 4-glucanohydrolase, EC 3.2.1.4] from Penicillium funiculosum have been determined. The Michaelis constants (K_m) for 4-nitrophenyl β- -glucopyranoside (4NPG) and cellobiose are 0.4 and 2.1 mM, respectively, at pH 4.0 and 50°C. -Glucose is shown to be a competitive inhibitor with inhibitor constants (K_i) of 1.7 mM when 4NPG is the substrate and 1 mM when cellobiose is the substrate. Cellobiose, at high concentrations, exhibits a substrate inhibition effect on the enzyme. -Glucono-1,5-lactone is shown to be a potent inhibitor (K_i = 8 μM; 4NPG as substrate) while -fructose exhibits little inhibition. Cellulose hydrolysis progress curves using Avicel or Solka Floc as substrates and a range of commercial cellulase preparations show that CP cellulase gives the best performance, which can be attributed to the activity of the β- -glucosidase in this preparation in maintaining the cellobiose at low concentrations during cellulose hydrolysis.