Enzymatic hydrolysis involves complex interaction between enzyme, substrate, and the reaction environ-
ment, and the complete mechanism is still unknown. Further, glucose release slows significantly as the
reaction proceeds. A model based on Langmuir binding kinetics that incorporates inactivation of
adsorbed cellulase was developed that predicts product formation within 10% of experimental results
for two substrates. A key premise of the model, with experimental validation, suggests that Vmax
decreases as a function of time due to loss of total available enzyme as adsorbed cellulases become inac-
tivated. Rate constants for product formation and enzyme inactivation were comparable to values
reported elsewhere. A value of k2/Km that is several orders of magnitude lower than the rate constant
for the diffusion-controlled encounter of enzyme and substrate, along with similar parameter values
between substrates, implies a common but undefined rate-limiting step associated with loss of enzyme
activity likely exists in the pathway of cellulose hydrolysis.