Lead poisoning in battery workers causes inhibition of which two specific enzymes, producing elevated urinary aminolaevulinic acid (ALA) and erythrocyte zinc protoporphyrin (ZPP) as biomarkers?

• A Delta-aminolaevulinic acid synthase (ALAS) and porphobilinogen deaminase
• B Uroporphyrinogen decarboxylase and coproporphyrinogen oxidase
• C Haem oxygenase and biliverdin reductase
• D ALA dehydratase (ALAD) and ferrochelatase ✓

Explanation

Lead inhibits two key haem synthesis enzymes: (1) ALA dehydratase (ALAD), which converts delta-ALA to porphobilinogen — its inhibition causes accumulation of urinary ALA; and (2) ferrochelatase (haem synthetase), which incorporates iron into protoporphyrin IX — its inhibition causes zinc to substitute for iron, producing zinc protoporphyrin (ZPP), a fluorescent biomarker detectable in erythrocytes. Both urinary ALA and erythrocyte ZPP are the most sensitive early biomarkers of lead exposure before overt toxicity occurs.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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