Question

How does a noncompetitive inhibitor decrease the rate of an enzyme-catalyzed reaction?A) by binding to the active site of the enzyme, thus preventing binding of the normal substrateB) by binding to an allosteric site, thus changing the shape of the active site of the enzymeC) by decreasing the free-energy change of the reaction catalyzed by theenzymeD) by binding to the substrate, thus changing its shape so that it no longerbinds to the active site of the enzyme

Answer 1

The right answer is B.

A noncompetitive inhibitor is an enzyme inhibitor that acts by binding, with equal affinity, both to the enzyme whose active site is free and to the complex formed by the enzyme and its substrate (unlike a competitive inhibitor which binds only to an enzyme whose active site is free); if this inhibitor has a higher affinity for the enzyme alone or for the enzyme-substrate complex, it is a mixed inhibitor.

Non-competitive inhibitors are allosteric, that is, they bind to other than the active site of the enzyme.