Heme synthesis

80% of heme biosynthetic production occurs in the bone marrow, where in combines with globin to form erythroid cells.

The remainder of the heme is produced in the liver and in cells outside the liver to make cytochrome P450 enzymes and other proteins.

Heme synthesis begins in the mitochondria with succinyl-CoA and glycine. 

Heme synthesis involves eight steps, each with a unique enzyme that advances the precursor products along the pathway. 

The enzyme that initiates the synthesis pathway, delta-aminolevulinic  acid synthase differs in the liver and bone marrow as does the regulatory feedback control. 

Disruptions in the pathway resulting from enzyme deficiencies cause precursors to accumulate.

The accumulation of porphyrin precursors delta aminolevulanic acid, porrphobilinogen, or porphyrins, uroporphyrin, coproporhyrin leads the clinical features of porphyria.

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