Delta-aminolevulinic acid, the precursor of all porphyrins, is formed by the condensation of which two substrates?

• A Succinyl-CoA and alanine
• B Alpha-ketoglutarate and glycine
• C Acetyl-CoA and serine
• D Succinyl-CoA and glycine ✓

Explanation

In the mitochondrion, ALA synthase condenses succinyl-CoA (from the TCA cycle) with glycine to form delta-aminolevulinic acid, releasing CO2. The TCA link explains why hepatic ALAS1 is induced when heme demand rises for cytochrome P450 synthesis. Alanine, alpha-ketoglutarate, acetyl-CoA and serine participate in other pathways and are standard distractors for this well-examined first step.

Reference: Lippincott's Illustrated Reviews: Biochemistry, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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