Question

Glucose is incubated with enzymes of glycolytic pathway (except pyruvate kinase), gamma \( ^{32}P \)-ATP and unlabeled inorganic phosphate. Which of the following products is/are formed? 

• A. (A)
• B. (B)
• C. (C)
• D. (D)

Hint:

In biochemical reactions involving ATP, the high-energy phosphate groups are transferred to intermediates in the pathway. These can be labeled using radioactive isotopes like \( ^{32}P \).

Answer 1

The Correct Option is A, B, D

Glycolysis pathway steps (relevant here):

1. Hexokinase: Glucose + ATP → Glucose-6-phosphate + ADP
2. Phosphoglucose isomerase: Glucose-6-phosphate → Fructose-6-phosphate
3. Phosphofructokinase: Fructose-6-phosphate + ATP → Fructose-1,6-bisphosphate + ADP
4. Aldolase: Fructose-1,6-bisphosphate → DHAP + G3P
5. Triose phosphate isomerase: DHAP ⟷ G3P
6. Glyceraldehyde-3-phosphate dehydrogenase: G3P + Pi + NAD⁺ → 1,3-BPG + NADH
7. Phosphoglycerate kinase: 1,3-BPG + ADP → 3-PG + ATP
8. Phosphoglycerate mutase: 3-PG → 2-PG
9. Enolase: 2-PG → PEP
10. Pyruvate kinase: PEP + ADP → Pyruvate + ATP (ABSENT)

Analyzing radioactive label incorporation:

(A) Glucose-6-phosphate with ³²P

From hexokinase reaction: Glucose + ³²P-ATP → Glucose-6-³²phosphate The γ-phosphate from ATP is transferred to glucose. Formed 

(B) Fructose-1,6-bisphosphate with ³²P

• Position 6: From ³²P-ATP via hexokinase → phosphoglucose isomerase
• Position 1: From ³²P-ATP via phosphofructokinase

Both phosphates come from ³²P-ATP. Formed 

(C) 1,3-Bisphosphoglycerate with ³²P

1,3-BPG is formed by glyceraldehyde-3-phosphate dehydrogenase:

• The phosphate at position 3 comes from G3P (originally from ³²P-ATP)
• The phosphate at position 1 (acyl phosphate) comes from unlabeled inorganic phosphate

So 1,3-BPG would have ³²P only at position 3, not at position 1. The structure shown in (C) suggests both positions are labeled, which is not fully correct. Not formed as shown 

(D) 3-Phosphoglycerate with ³²P

3-PG is formed from 1,3-BPG by phosphoglycerate kinase:

• The phosphate at position 3 comes from G3P (originally from ³²P-ATP)
• The acyl phosphate at position 1 is transferred to ADP

3-PG retains the ³²P at position 3. Formed 

Answer: (A), (B), and (D)