Question

Which of the following is true of Gly-10 (pyruvate kinase), which converts phosphoenol pyruvate to pyruvate?

a. It is a highly endergonic reaction.
b. It is an example of substrate-level phosphorylation, producing ATP.
c. It is set up by Gly-9 (enolase), which converts a phosphoenol bond to a phosphoester bond.
d. It is readily reversible.

Answer 1

Pyruvate kinase catalyzes an exergonic and effectively irreversible reaction in glycolysis, converting phosphoenolpyruvate to pyruvate and producing ATP through substrate-level phosphorylation.

Step-by-step explanation:

The reaction catalyzed by the enzyme pyruvate kinase, which converts phosphoenolpyruvate (PEP) to pyruvate, is an important step in the glycolytic pathway. Contrary to an endergonic reaction, this step is highly exergonic, releasing energy that is utilized to convert ADP to ATP in a process known as substrate-level phosphorylation.

Therefore, the correct statement about this enzyme is that it is involved in substrate-level phosphorylation, producing ATP. Additionally, although many enzymatic reactions in glycolysis can proceed in both directions under certain conditions, the conversion of PEP to pyruvate by pyruvate kinase is highly exergonic and thus, under physiological conditions, is considered effectively irreversible.