Uroporphyrinogen III C methyltransferase

Uroporphyrinogen-III C-methyltransferase (EC 2.1.1.107, uroporphyrinogen methyltransferase, uroporphyrinogen-III methyltransferase, adenosylmethionine-uroporphyrinogen III methyltransferase, S-adenosyl-L-methionine-dependent uroporphyrinogen III methylase, uroporphyrinogen-III methylase, SirA, CysG, uroporphyrin-III C-methyltransferase, S-adenosyl-L-methionine:uroporphyrin-III C-methyltransferase) is an enzyme with systematic name S-adenosyl-L-methionine:uroporphyrinogen-III C-methyltransferase. This enzyme catalyses the following chemical reaction

2 S-adenosyl-L-methionine + uroporphyrinogen III ⇌ 2 S-adenosyl-L-homocysteine + precorrin-2 (overall reaction) (1a) S-adenosyl-L-methionine + uroporphyrinogen III ⇌ S-adenosyl-L-homocysteine + precorrin-1 (1b) S-adenosyl-L-methionine + precorrin-1 ⇌ S-adenosyl-L-homocysteine + precorrin-2

Uroporphyrinogen-III C-methyltransferase catalyses two methylation reactions, the first forming precorrin-1 and the second leading to the formation of precorrin-2.