Substrate-concentration dependences of the apparent, maximum-reaction rate and Michaelis-Menten constant in immobilized enzyme reactions

Expressions are proposed for the apparent-rate parameters V_m^app and K_m^app of an immobilized-enzyme reaction with diffusional and electrostatic effects, based on the equation for the tangent of the S_b/v-S_b curve. The validities of the expressions are demonstrated by comparing the expression for the apparent Michaelis constant K_m^app with two approximate expressions proposed elsewhere for an enzyme-catalyzed reaction with the enzyme immobilized on the surface of a nonporous support. Calculations showed that the effect of the substrate concentration of V_m^app and K_m^app was, fundamentally, different in a system where the catalyst was immobilized on the exterior surface of support, and in a system where it was immobilized on the surface of the pores.