Rapid equilibrium steps resolving

In the example involving the binding of S3P and glyphosate, it was relatively easy to resolve the two-step reaction kinetics because of the separate concentration dependence for each step the first step depended on S3P and the second on glyphosate. Moreover, substrate trapping studies established that S3P dissociates at a very fast rate (i), justifying the rapid equilibrium assumption. With the... 

Iwatsubo and Pantaloni 121) demonstrated that the rate-limiting step in oxidation of glutamate is release of the reduced coenzyme, confirming an earlier conclusion based on steady-state measurements 315). Subsequently, Fisher et al. 322) and DiFranco and Iwatsubo 323) indicated that reduction of NADP can be resolved into a three-part process, a rapid, first-order burst followed by a slower, zero-order, second phase, then an approach to equilibrium. Fisher et al. 322) demonstrated that replacement of the a-hydrogen of the substrate by deuterium results in a significant slowing of the burst phase but has little effect on subsequent steps, thus indicating that hydride ion abstraction is involved in the burst. 

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