Biosynthesis of Siroheme and Coenzyme F430

Abstract

The biosynthesis of siroheme from uropoprhyirnogen III in bacteria, yeasts and plants is described. The pathway requires the bis-methylation of uroporphyrinogen III to generate precorrin-2, which is then oxidised to sirohydrochlorin prior to its ferrochelation. A number of structures of the various biosynthetic enzymes have been elucidated and thus the overall process is known in molecular detail. In contrast, the biosynthesis of coenzyme F430, which is synthesized soley by methanogenic bacteria, is poorly understood. It is estimated that between 6 and 8 steps are required for the transformation of uroporphyrinogen III into coenzyme F430, yet none of the biosynthetic enzymes have been identified and only one potential intermediate has been isolated.