Question

Phosphofructokinase (PFK) is an enzyme that converts fructose 6-phosphate to fructose 1,6-bisphosphate, by adding a phosphate group. This is the first committed step of the metabolic pathway of glycolysis, and thus it is very tightly regulated. AMP binds to PFK at a site distinct from the binding site for fructose 6-phosphate, and stimulates the formation of fructose 1,6-bisphosphate. ATP binds to PFK at a site distinct from the binding site for fructose 6-phosphate, and inhibits the formation of fructose 1,6-bisphosphate. There are other regulators of this enzyme as well. What is the role of AMP in this example?
A. Competitive inhibitor
B. Noncompetitive inhibitor
C. Allosteric inhibitor
D. Allosteric activator
E. Catalyst

Answer 1

Answer:

D. Allosteric activator

Explanation:

In an enzyme, the allosteric site is a site/motif different from the active site, (i.e., the site with catalytic activity) which is able to interact with regulatory effector molecules in order to activate or inhibit enzymatic activity by influencing the tridimensional (3D) structure of the enzyme. An allosteric activator is an effector molecule with the ability to bind to a specific enzyme at a different site than the active site, thereby modifying the shape of the enzyme and increasing the affinity of this enzyme for its substrate. Moreover, Adenosine monophosphate (AMP) is a nucleotide composed of a phosphate group, a sugar ribose, and an Adenine (A) base. This effector molecule (AMP) has shown to allosterically stimulate diverse enzymes in physiological conditions (e.g., AMP-activated protein kinase).