Question

What does it mean when you are told that "ATP is an allosteric inhibitor" of an enzyme? Your answer should address both allosteric and inhibitor.

Answer 1

Ans.

A compound when binds to the allosteric site of an enzyme changes the protein configuration of active site and therefore inactivate that enzyme, then it is called an allosteric inhibitor.

   "ATP is an allosteric inhibitor" of an enzyme means that the high concentration of ATP can inactive an enzyme by phosphorylating it and causes a conformational change of the enzyme in active site and inhibit the function of enzyme.

As for example, ATP is an allosteric inhibitor of pyruvate kinase in the process of glycolysis. In the last step of glycolysis pyruvate kinase helps to convert phosphoenol pyruvate (PEP) to pyruvate and transfer the phosphate group attached to the 2' carbon of PEP to the ADP, forming ATP. This ATP binds to the allosteric site of pyruvate kinase and change its conformation in active site.