IUBMB Enzyme Nomenclature


Accepted name: tRNA (N6-L-threonylcarbamoyladenosine37-C2)-methylthiotransferase

Reaction: N6-L-threonylcarbamoyladenine37 in tRNA + sulfur-(sulfur carrier) + 2 S-adenosyl-L-methionine + reduced electron acceptor = 2-(methylsulfanyl)-N6-L-threonylcarbamoyladenine37 in tRNA + S-adenosyl-L-homocysteine + (sulfur carrier) + L-methionine + 5'-deoxyadenosine + electron acceptor (overall reaction)
(1a) N6-L-threonylcarbamoyladenine37 in tRNA + sulfur-(sulfur carrier) + S-adenosyl-L-methionine + reduced electron acceptor = 2-thio-N6-L-threonylcarbamoyladenine37 in tRNA + (sulfur carrier) + L-methionine + 5-deoxyadenosine + electron acceptor
(1b) S-adenosyl-L-methionine + 2-thio-N6-L-threonylcarbamoyladenine37 in tRNA = S-adenosyl-L-homocysteine + 2-(methylsulfanyl)-N6-L-threonylcarbamoyladenine37 in tRNA

For diagram of reaction click here.

Glossary: N6-L-threonylcarbamoyladenine37 = t6A37
2-thio-N6-L-threonylcarbamoyladenine37 = ms2t6A37

Other name(s): MtaB; methylthio-threonylcarbamoyl-adenosine transferase B; CDKAL1 (gene name); tRNA (N6-L-threonylcarbamoyladenosine37):sulfur-(sulfur carrier),S-adenosyl-L-methionine C2-methylthiotransferase

Systematic name: tRNA (N6-L-threonylcarbamoyladenosine37):sulfur-(sulfur carrier),S-adenosyl-L-methionine C2-(methylsulfanyl)transferase

Comments: The enzyme, which is a member of the S-adenosyl-L-methionine-dependent radical (radical AdoMet) enzymes superfamily, binds two [4Fe-4S] clusters as well as the transferred sulfur. The sulfur donor is believed to be one of the [4Fe-4S] clusters, which is sacrificed in the process, so that in vitro the reaction is a single turnover. The identity of the electron donor is not known.

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:


1. Arragain, S., Handelman, S.K., Forouhar, F., Wei, F.Y., Tomizawa, K., Hunt, J.F., Douki, T., Fontecave, M., Mulliez, E. and Atta, M. Identification of eukaryotic and prokaryotic methylthiotransferase for biosynthesis of 2-methylthio-N6-threonylcarbamoyladenosine in tRNA. J. Biol. Chem. 285 (2010) 28425-28433. [PMID: 20584901]

[EC created 2014, modified 2015]

Return to EC 2.8.4 home page
Return to EC 2.8 home page
Return to EC 2 home page
Return to Enzymes home page
Return to IUBMB Biochemical Nomenclature home page