IUBMB Enzyme Nomenclature


Accepted name: tRNA carboxymetyluridine synthase

Reaction: acetyl-CoA + uridine34 in tRNA + S-adenosyl-L-methionine + H2O = CoA + 5-(carboxymethyl)uridine34 in tRNA + L-methionine + 5'-deoxyadenosine

Other name(s): elongator complex; ELP3

Systematic name: acetyl-CoA:tRNA uridine carboxymethyltransferase

Comments: The enzyme, found in eukaryotes, most archaea, and some bacteria, catalyses the first step in modification of the wobble uridine base of certain tRNAs. In eukaryotes the enzyme is a complex of six conserved subunits, with ELP3 being the catalytic subunit. In archaea and bacteria the enzyme consists of a single subunit, homologous to ELP3. The enzyme contains an [4Fe-4S] cluster and uses radical chemistry. A 5'-deoxyadenosyl radical generated in the radical AdoMet (SAM) domain attacks the acetyl-CoA donor, activating its methyl group, which forms a C-C bond with C5 of the uridine moiety.

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


1. Paraskevopoulou, C., Fairhurst, S.A., Lowe, D.J., Brick, P. and Onesti, S. The Elongator subunit Elp3 contains a Fe4S4 cluster and binds S-adenosylmethionine. Mol. Microbiol. 59 (2006) 795-806. [PMID: 16420352]

2. Selvadurai, K., Wang, P., Seimetz, J. and Huang, R.H. Archaeal Elp3 catalyzes tRNA wobble uridine modification at C5 via a radical mechanism. Nat. Chem. Biol. 10 (2014) 810-812. [PMID: 25151136]

3. Lin, T.Y., Abbassi, N.EH., Zakrzewski, K., Chramiec-Glabik, A., Jemiola-Rzeminska, M., Rozycki, J. and Glatt, S. The Elongator subunit Elp3 is a non-canonical tRNA acetyltransferase. Nat. Commun. 10 (2019) 625. [PMID: 30733442]

[EC created 2022]

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