Question

1. Use the following information to answer the question below.
   
   A series of enzymes catalyze the reaction X → Y → Z → A.  Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme.
   
   
   With respect to the enzyme that converts X to Y, substance A is  best described as being what?

   		a feedback inhibitor
   		a noncompetive inhibitor
   		cooperative
   		a competitive inhibitor

Answer 1

The correct option is 'A feedback inhibitor'.

Feedback inhibition is a form of allosteric regulation in which the final product of a sequence of enzymatic reactions, when accumulates in abundance, binds to an allosteric site on the first enzyme in the series of reactions to inhibit its activity.

The competitive inhibitor binds to the active site and prevents the substrate from binding there. The non-competitive inhibitor binds to a different site on the enzyme, without blocking substrate binding. It can cause other changes in the enzyme so that it can no longer function efficiently. Cooperativity is an ability of the enzymes that have multiple binding sites, where the affinity of the binding sites for a substrate is either increased or decreased upon the binding of a substrate to a binding site.