Which enzyme of the ones shown below generates the first intermediate compound with a high phosphoryl‑transfer potential that is not ATP

Question

Which enzyme of the ones shown below generates the first intermediate compound with a high phosphoryl‑transfer potential that is not ATP

BlackTom AI · Accepted Answer

To determine which enzyme generates the first intermediate with high phosphoryl-transfer potential that is not ATP, we need to trace glycolytic steps and the nature of the high-energy intermediates formed.
Option 1: aldolase. This enzyme splits fructose-1,6-bisphosphate into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. While it is a key glycolytic enzyme, the reaction does not produce a high-energy phosphate compound itself; it simply cleaves a fructose-bisphosphate to generate triose phosphates. Therefore this option does not describe the generation of a high-energy phosphorylated intermediate.
Option 2: hexokinase. This enzyme catalyzes the phosphorylation of glucose to glucose-6-phosphate using one ATP molecule, introducing a phosphate and consuming ATP. The product is glucose-6-phosphate, which is a phosphorylated sugar, but it is not characterized by a high phosphoryl‑transfer potential intermediate formed in the subsequent steps; furthermore, the question asks for the first intermediate with high phosphoryl-transfer potential that is not ATP, which points to a later step after the initial ATP investment.
Option 3: glyceraldehyde 3-phosphate dehydrogenase. This enzyme oxidizes glyceraldehyde-3-phosphate and adds an inorganic phosphate to form 1,3-bisphosphoglycerate. This reaction produces a high-energy acyl-phosphate intermediate (1,3-bisphosphoglycerate) with a high phosphoryl-transfer potential and, importantly, it is not ATP itself. The appearance of this intermediate represents the first instance in glycolysis of a high-energy phosphate-bearing compound that is not ATP, aligning with the question’s specification.
Option 4: phosphoglucose isomerase. This enzyme converts glucose-6-phosphate to fructose-6-phosphate, an isomerization step. It does not generate any high-energy phosphate-containing intermediate; it merely rearranges the carbonyl and hydroxyl positions. Consequently, it does not meet the criterion of forming a high-energy phosphoryl-transfer intermediate.
In summary, among the listed enzymes, the step catalyzed by glyceraldehyde 3-phosphate dehydrogenase uniquely generates 1,3-bisphosphoglycerate, a high-energy phosphoryl-transfer intermediate that is not ATP, whereas the other options either do not generate such an intermediate or are involved in earlier ATP-dependent phosphorylation or non-energetic rearrangements.

Which enzyme of the ones shown below generates the first intermediate compound with a high phosphoryl‑transfer potential that is not ATP

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