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 functions as
A) a coenzyme.
B) an allosteric inhibitor.
C) the substrate.
D) an intermediate.
E) a competitive inhibitor.

Question

Quizplus · Accepted Answer

Substance A binds to the enzyme at a site remote from the active site, causing a conformational change that decreases the enzyme's activity. This behavior is characteristic of an allosteric inhibitor. A coenzyme is a small molecule that binds near the active site and is required for enzyme activity. The substrate is the molecule that the enzyme acts upon, and intermediate is a molecule formed during the reaction but is not a final product. A competitive inhibitor binds to the active site and competes with the substrate for binding.

A Series of Enzymes Catalyze the Reaction X → Y