|Molar mass||836.795 g/mol|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Its biosynthetic precursor is the linear tetrapyrrole hydroxymethylbilane, which is converted to uroporphyrinogen III by the action of uroporphyrinogen-III synthase. If, however, uroporphyrinogen-III synthase is not present, the hydroxymethylbilane will spontaneously cyclise into uroporphyrinogen I. The difference between the uroporphyrinogen I and III is the arrangement of the four propionic acid ("P" groups) and the four acetic acid groups ("A" groups). Uroporphyrinogen I features in an AP-AP-AP-AP symmetry, whereas in uroporphyrinogen III one AP-group is reversed and hence an AP-AP-AP-PA arrangement.
Conversion to heme and sirohemes, etc.
In the biosynthesis of sirohemes, uroporphyrinogen III is converted by two methyl transferases to dihydrosirohydrochlorin, which is subsequently oxidized sirohydrochlorin, a precursor to the siroheme prosthetic group. In the biosynthesis of hemes and chlorophylls, uroporphyrinogen III is converted into coproporphyrinogen III by the enzyme uroporphyrinogen III decarboxylase.