ABSTRACT
In Chapter 2 the overall initial velocity rate equation was discussed in terms of obtaining information on the kinetic mechanism of an enzyme-catalyzed reaction. The denominator of the rate equation was identified as providing information on the kinetic mechanism, while the numerator provides information on the thermodynamic driving force. The denominator of the rate equation represents a distribution of the enzyme among all the possible forms that could exist for a given enzyme-catalyzed reaction. Thus depending on the kinetic mechanism for an enzyme-catalyzed reaction, the overall rate equation will differ, and one attempts to determine what terms exist in the denominator of the rate equation to elucidate kinetic mechanism. In this chapter the general background for interpreting initial velocity data will be established by using initial velocity patterns in the absence of added inhibitors, exploiting differences that exist in the overall initial velocity rate equation, depending on the kinetic mechanism of the enzyme-catalyzed reaction. The Uni Bi mechanism is applicable to, among others, enzyme reactions such as those catalyzed by phosphatases like alkaline phosphatase and ammonia lyases such as aspartate ammonia-lyase. To illustrate the general procedure, two different Uni Bi kinetic mechanisms will be used, the 60Uni Bi steady-state ordered and Uni Bi rapid equilibrium random. The rate equation will be analyzed in the first section, and in the last section a procedure for collecting the initial velocity data will be outlined. Complete rate equations, in terms of rate constants and kinetic constants, along with distribution equations and Haldane relationships for a number of Uni-, Bi-, and Terreactant mechanisms, are provided in Appendix II.
