Glycolysis: the committed step and its regulation
Which glycolytic enzyme catalyzes the committed step of the pathway and is allosterically inhibited by ATP and citrate?
Answer B: explanation for every choice
Hexokinase catalyzes the first step, but glucose-6-phosphate can still enter glycogen synthesis or the pentose phosphate pathway, so it is not committed. It is inhibited by its product, G6P.
Correct. PFK-1 converts fructose-6-phosphate to fructose-1,6-bisphosphate, the first step unique to glycolysis. It is inhibited by ATP and citrate and activated by AMP and fructose-2,6-bisphosphate.
Pyruvate kinase is a regulated, irreversible step, but it comes last. It is feed-forward activated by fructose-1,6-bisphosphate and is not the committed step.
GAPDH generates NADH and is not a major allosteric control point.
Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID bb2.