InterPro domain: IPR006366

SUMT, an enzyme of the cobalamin and siroheme biosynthetic pathway, catalyses the transformation of uroporphyrinogen III into precorrin-2. It transfers two methyl groups from S-adenosyl-L-methionine to the C-2 and C-7 atoms of uroporphyrinogen III to yield precorrin-2 via the intermediate formation of precorrin-1. SUMT is the first enzyme committed to the biosynthesis of siroheme or cobalamin (vitamin B12), and precorrin-2 is a common intermediate in the biosynthesis of corrinoids such as vitamin B12, siroheme and coenzyme F430 [ 1 , 2 ].

In some organisms, the SUMT domain is fused to the precorrin-2 oxidase/ferrochelatase domain to form siroheme synthase or to uroporphyrinogen-III synthase to form bifunctional uroporphyrinogen-III methylase/uroporphyrinogen-III synthase.

1. Structure/function studies on a S-adenosyl-L-methionine-dependent uroporphyrinogen III C methyltransferase (SUMT), a key regulatory enzyme of tetrapyrrole biosynthesis. J. Mol. Biol. 344, 419-33
2. Structure of a closed-form uroporphyrinogen-III C-methyltransferase from Thermus thermophilus. Acta Crystallogr. D Biol. Crystallogr. 61, 913-9