초록
<P><B>Highlights</B></P><P>► Development of kinetic model based on inactivation of adsorbed cellulase. ► Model predicts within 10% of experimental results for two substrates. ► <I>V</I><SUB>max</SUB> decreases with time as adsorbed cellulases become inactivated. ► An undefined rate-limiting step likely exists during cellulose hydrolysis.</P> <P><B>Abstract</B></P><P>Enzymatic hydrolysis involves complex interaction between enzyme, substrate, and the reaction environment, 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 <I>V</I><SUB>max</SUB> decreases as a function of time due to loss of total available enzyme as adsorbed cellulases become inactivated. Rate constants for product formation and enzyme inactivation were comparable to values reported elsewhere. A value of <I>k</I><SUB>2</SUB>/<I>K</I><SUB>m</SUB> 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.</P>