In erythrocytes, 2,3-bisphosphoglycerate (2,3-BPG) binds to deoxyhemoglobin and reduces its oxygen affinity. The Rapoport-Luebering shunt that produces 2,3-BPG diverts which glycolytic intermediate away from ATP generation?

• A Glucose-6-phosphate
• B Fructose-1,6-bisphosphate
• C Phosphoenolpyruvate
• D 1,3-Bisphosphoglycerate ✓

Explanation

The Rapoport-Luebering shunt converts 1,3-BPG to 2,3-BPG via bisphosphoglycerate mutase, bypassing phosphoglycerate kinase (which would generate ATP). 2,3-BPG is then converted to 3-phosphoglycerate by 2,3-BPG phosphatase, also without ATP generation. Thus one ATP per glucose is sacrificed to produce 2,3-BPG. Option D correctly identifies the diverted intermediate.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

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