Basic subsite theory assumptions may not be applicable to hydrolysis of cellooligosaccharides by almond beta-glucosidase

Steady-state kinetic parameters for the hydrolysis of cellooligosaccharides by almond beta-glucosldase were evaluated at pH 5.0 and 25 degrees C in re lation to the subsite theory (K. Hiromi, Biochem. Biophys. Res. Commun., 40 , 1-6, 1970). The value of k(0)/K-m decreased monotonously with increasing degree of polymerization (DP) of the substrates (DP =2-6). Also, the K-m an d k(0) values for cellotriose were smaller than those for cellobiose. These DP dependencies differ from those of most amylases and glucosidases studie d so far, to which the subsite theory has been successfully applied. The su bsite parameters could not be consistently obtained, which suggests that on e or both of the two basic assumptions of the subsite theory might not be a pplicable to the hydrolysis of cellooligosaccharides by the enzyme. That is , the intrinsic rate of the hydrolysis may depend on the DP and/or there ma y be interaction between subsites for binding the glucose residues of a sub strate.