Reaction: S-adenosyl-L-methionine + L-tryptophan = S-adenosyl-L-homocysteine + L-2-methyltryptophan
Other name(s): tsrM (gene name); tryptophan 2-methyltransferase; S-adenosylmethionine:tryptophan 2-methyltransferase
Systematic name: S-adenosyl-L-methionine:L-tryptophan 2-C-methyltransferase
Comments: The enzyme, characterized from the bacterium Streptomyces laurentii, is involved in thiostrepton biosynthesis. It is a radical SAM enzyme that contains a [4Fe-4S] center and a cobalamin cofactor. The enzyme first transfers the methyl group from SAM to the bound cobalamin, followed by transfer from methylcobalamin to L-tryptophan, resulting in retention of the original methyl group configuration. The second transfer is likely to involve a CH3 radical species formed from methylcobalamin by the concerted action of a partially ligated radical SAM [4Fe-4S]2+/1+ center.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number: 126626-83-3
1. Frenzel, T., Zhou, P. and Floss, H.G. Formation of 2-methyltryptophan in the biosynthesis of thiostrepton: isolation of S-adenosylmethionine:tryptophan 2-methyltransferase. Arch. Biochem. Biophys. 278 (1990) 35-40. [PMID: 2321967]
2. Pierre, S., Guillot, A., Benjdia, A., Sandstrom, C., Langella, P. and Berteau, O. Thiostrepton tryptophan methyltransferase expands the chemistry of radical SAM enzymes. Nat. Chem. Biol. 8 (2012) 957-959. [PMID: 23064318]