Villagers drinking water with very high fluoride content develop mottled enamel and later stiffness and calcification of spinal ligaments. Which glycolytic enzyme does fluoride directly inhibit, a property exploited in laboratory tubes used for glucose estimation?
- A Enolase ✓
- B Pyruvate kinase
- C Hexokinase
- D Glyceraldehyde-3-phosphate dehydrogenase
Correct answer: A. Enolase
Explanation
Fluoride forms a magnesium-fluorophosphate complex at the active site of enolase, the enzyme converting 2-phosphoglycerate to phosphoenolpyruvate. This inhibition blocks glycolysis below the phosphoenolpyruvate step, which is why sodium fluoride tubes preserve blood glucose by stopping ongoing erythrocyte glycolysis. Chronic excess fluoride causes dental fluorosis in children and skeletal fluorosis in adults. Hexokinase, pyruvate kinase, and GAPDH are not inhibited by fluoride in this manner.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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