Conversion into 8-aminolevulinic acid

Finally, it is widely known that Pb impairs the formation of red blood cells. The mechanism involved in the impairment is that Pb inhibits both 5-aminolevulinic acid dehydratase (ALA-D) (Hernberg et al. 1970) and ferrochelatase (Tephly et al. 1978). These are two key enzymes involved in heme biosynthesis. ALA-D catalyzes the conversion of 5-aminolevulinic acid into porphobilinogen (PBG), whereas ferrochelatase is responsible for catalyzing the incorporation of Fe2+ into protoporphyrin IX to form heme (Figure 9.1). Lead inhibition of the two enzymes appears to be due to its interaction with Zn and Fe required in the process. 

Kloek, J., Akkermans, W., and Beijersbergen van Henegouwen, G.M.J. (1998) Derivatives of 5-aminolevulinic acid for photodynamic therapy enzymatic conversion into protoporphyrin, Photochem. Photobiol., 67 150-154. 

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