Chapter 19, Problem 19.45QP

Interpretation Introduction

Interpretation:

The lock and key model for the enzyme-substrate binding have to be determined.

Concept Introduction:

In an enzyme-catalyzed reaction first the enzyme and substrate approaches, form an enzyme-substrate complex that undergoes some transformation to form enzyme product and finally the enzyme is removed from the substrate. 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 as follows:

  $\begin{array}{l}\text{ ES }\stackrel{\text{Step 2}}{\rightleftarrows }{\text{ ES}}^{*}\stackrel{\text{Step 3}}{\rightleftarrows }\text{ EP}\\ \left[\text{Enzyme-substrate}\right]\text{ Transition state }\left[\text{Enzyme-product}\right]\end{array}$

Finally, the enzyme product complex decomposes to give product and the enzyme is liberated.

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