Lead and the terminal mitochondrial enzymes of haem biosynthesis.
Lead exposure causes increases in urinary coproporphyrin excretion and the accumulation of zinc protoporphyrin in red cells. In the conventional view of the effect of lead on haem biosynthesis, the accumulation of these metabolites results from lead inhibition of two of the mitochondrial enzymes of haem biosynthesis, coproporphyrinogen oxidase (EC 1.3.3.3) and ferrochelatase (EC 4.99.1.1). This review critically assesses the evidence for the inhibition of these enzymes. We consider this evidence to be inconclusive and alternative explanations for the increased concentrations of coproporphyrin and zinc protoporphyrin are proposed.
Rossi
E
E
Clinical Biochemistry Department, Queen Elizabeth II Medical Centre, Nedlands, W.A., Australia.
Taketani
S
S
Garcia-Webb
P
P
D000818:Animals; D003304:Coproporphyrinogen Oxidase / Q000037:antagonists & inhibitors; D005294:Ferrochelatase / Q000037:antagonists & inhibitors; D006418:Heme / Q000096:biosynthesis*; D006801:Humans; D007854:Lead / Q000633:toxicity*; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology*
D007854:Lead; D006418:Heme; D003304:Coproporphyrinogen Oxidase; D005294:Ferrochelatase