Chapter 19, Problem 19.58QP

Interpretation Introduction

Interpretation:

The term transition state of the reaction has to be described.

Concept Introduction:

In an enzyme-catalyzed reaction firstly the enzyme and substrate approach to form an enzyme-substrate complex that undergoes some transformation to form enzyme product and finally the enzyme is removed from the substrate and the product formed is released off.

The key steps of an enzyme-catalyzed reaction can be illustrated as follows:

  $\begin{array}{l}\text{E}+\text{S }\stackrel{\text{Step }1}{\rightleftarrows }\text{ ES}\\ \left(\text{Enzyme-substrate}\right)\end{array}$

This enzyme-substrate thus formed undergoes a transformation to form a transition state as follows:

  $\begin{array}{l}\text{ ES }\stackrel{\text{Step 2}}{\rightleftarrows }{\text{ ES}}^{*}\\ \left[\text{Enzyme-substrate}\right]\text{ Transition state}\end{array}$

${\text{ES}}^{*}$ enables the transformation of the substrate to the desired product as indicated in step 3 below:

  $\begin{array}{l}{\text{ ES}}^{*}\stackrel{\text{Step 3}}{\rightleftarrows }\text{ EP}\\ \text{Transition state }\left[\text{Enzyme-product}\right]\end{array}$

Finally, the enzyme-product complex decomposes to give product, and the enzyme is liberated as illustrated below:

  $\text{EP}\stackrel{\text{Step 4}}{\rightleftarrows }\text{E}+\text{P}$