What is allosteric inhibitor?

Jan 29, 2018

A non-competitive inhibitor which attaches to the enzyme at allosteric site i.e any place on enzyme except active site, is called allosteric inhibitor.

Explanation:

An allosteric inhibitor by binding to allosteric site alters the protein conformation in active site of enzyme which consequently changes the shape of active site. Thus enzyme no longer remains able to bind to its specific substrate. Hence enzyme is unable to perform it's catalytic activity i.e enzyme is now inactive. This process is called allosteric inhibition.

For example: $\text{ATP}$ act as allosteric inhibitor of enzyme pyruvate kinase during glycolysis. Pyruvate kinase speeds up the last step of glycolysis by transferring the phosphate from phosphoenol pyruvate$\left(\text{PEP}\right)$ to $\text{ADP}$ to form $\text{ATP}$. The formed $\text{ATP}$ itself distorts the shape of the active site by binding to the allosteric site of pyruvate kinase. Hence it actually act as allosteric inhibitor in this case.

Hope it helps...