Two ligands, A and B, bind to two different conformations of the enzyme X. The ligand A is the enzyme's substrate, whereas ligand B binds to a remote allosteric site. Which of the following is a consequence of this arrangement?
A) Binding of A to X does not affect the affinity of X for binding to B.
B) Binding of B to X does not affect the rate of reaction catalyzed by X.
C) Binding of A to X increases the affinity of X for B.
D) Binding of B to X decreases the affinity of X for A.
E) Binding of B to X has a large effect on the binding of A to X, but binding of A to X has a small effect on X-B binding.

Question

Quizplus · Accepted Answer

Due to the negative "linkage" between the two binding events, binding of each of the two ligands to the enzyme reduces the affinity of the enzyme for the other ligand, and this effect is quantitatively reciprocal as well.

Two Ligands, a and B, Bind to Two Different Conformations