uroporphyrin-III C-methyltransferase activity

Catalysis of the reaction: 2 S-adenosyl-L-methionine + uroporphyrin III = 2 S-adenosyl-L-homocysteine + precorrin-2.

CobA, CysG, S-adenosyl-L-methionine-dependent uroporphyrinogen III methylase activity, S-adenosyl-L-methionine:uroporphyrin-III C-methyltransferase activity, S-adenosyl-L-methionine:uroporphyrinogen-III C-methyltransferase activity, SUMT activity, SirA, adenosylmethionine-uroporphyrinogen III methyltransferase activity, urogen III methylase activity, uroporphyrin-III C-methyltransferase activity, uroporphyrinogen III methylase activity, uroporphyrinogen methyltransferase activity, uroporphyrinogen-III C-methyltransferase activity, uroporphyrinogen-III methylase activity, uroporphyrinogen-III methyltransferase activity