Figure 1.
Effect of lead on heme synthesis. Lead inhibits (┤) 5-aminolevulic acid dehydratase, coproporphyrinogen oxidase, and ferrochelatase. Inhibition of ferrochelatase increases free protophorphyrin IX which chelates with zinc and forms zinc protoporphyrin within the erythroctes, a marker of lead exposure within the past 3 months.