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-glucosidase were evaluated at pH 5.0 and 25 degrees C in relation to the subsite theory (K. Hiromi, Biochem. Biophys. Res. Commun., 40, 1-6, 1970). The value of k0/Km decreased monotonously with increasing degree of polymerization (DP) of the substrates (DP = 2-6). Also, the Km and k0 values for cellotriose were smaller than those for cellobiose. These DP dependencies differ from those of most amylases and glucosidases studied so far, to which the subsite theory has been successfully applied. The subsite parameters could not be consistently obtained, which suggests that one or both of the two basic assumptions of the subsite theory might not be applicable to the hydrolysis of cellooligosaccharides by the enzyme. That is, the intrinsic rate of the hydrolysis may depend on the DP and/or there may be interaction between subsites for binding the glucose residues of a substrate.
Tanaka
A
A
Faculty of Bioresources, Mie University, Tsu, Mie 514-8507, Japan.
Nakagawa
C
C
Kodaira
K
K
Senoo
K
K
Obata
H
H