Chapter 19, Problem 7MCP

Interpretation Introduction

Interpretation:

The step in the following pathway that must be regulated has to be explained.

Concept Introduction:

Feedback inhibition serves as an effective metabolic on-off switch mechanism to regulate the activity of an enzyme. The key role in feedback inhibition is played by the allosteric enzymes

The feedback regulation can be understood from the synthetic pathway given as follows:

  $\text{A}\stackrel{{\text{E}}_{\text{1}}}{\to }\text{B}\stackrel{{\text{E}}_{\text{2}}}{\to }\text{C}\stackrel{{\text{E}}_{\text{3}}}{\to }\text{D}\stackrel{{\text{E}}_{\text{4}}}{\to }\text{E}\stackrel{{\text{E}}_{\text{5}}}{\to }\text{F}$

When the concentration of the final product F exceeds the desired concentration than the cycle is automatically shut off. So, here the product $\text{F}$ serves as the negative allosteric effector for the enzymes that start this synthetic pathway. Consequently, the activity of the enzyme ${\text{E}}_{\text{1}}$ is inhibited. With the inactivation of this enzyme that is required in the first of the synthetic steps the entire sequence of reaction ceases.