Overview Of The Tetrapyrrole Biosynthesis Pathway

The heme biosynthetic pathway together with the bifurcation points for the synthesis of the other modified tetrapyrroles is outlined in Figure 1. This chapter is structured around the various enzymes highlighted in the diagram, and considers the synthesis of the following compounds:

5-aminolevulinic acid porphobilinogen preuroporphyrinogen uroporphyrinogen III, using multiple enzymes precorrin-2, sirohydrochlorin and siro-

heme from uroporphyrinogen III coproporphyrinogen III protoporphyrinogen IX protoporphyrin IX from copropor-phyrinogen III, using multiple enzymes protoheme

Figure 1. Biosynthesis of heme from ALA. The figure also highlights uroporphyrinogen III as the branchpoint for siroheme and cobalamin synthesis. Abbreviations used: A, acetate side chain; p, propionate side chain.
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