IUBMB Enzyme Nomenclature


Accepted name: epoxyqueuosine reductase

Reaction: queuosine34 in tRNA + acceptor + H2O = epoxyqueuosine34 in tRNA + reduced acceptor

For diagram of reaction click here.

Glossary: queuine = base Q = 2-amino-5-({[(1S,4S,5R)-4,5-dihydroxycyclopent-2-en-1-yl]amino}methyl)-1,7-dihydropyrrolo[3,2-e]pyrimidin-4-one
epoxyqueine = base oQ

Other name(s): oQ reductase; queG (gene name); queH (gene name)

Systematic name: queuosine34 in tRNA:acceptor oxidoreductase

Comments: This enzyme catalyses the last step in the bacterial biosynthetic pathway to queuosine, the modified guanosine base in the wobble position in tRNAs specific for Tyr, His, Asp or Asn. Two types of enzymes are known to catalyse this activity. QueG enzymes are cobalamin-dependent, while QueH enzymes contain a [4Fe-4S] metallocluster along with an adjacent coordinated iron metal.

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


1. Miles, Z.D., McCarty, R.M., Molnar, G. and Bandarian, V. Discovery of epoxyqueuosine (oQ) reductase reveals parallels between halorespiration and tRNA modification. Proc. Natl. Acad. Sci. USA 108 (2011) 7368-7372. [PMID: 21502530]

2. Zallot, R., Ross, R., Chen, W.H., Bruner, S.D., Limbach, P.A. and de Crecy-Lagard, V. Identification of a novel epoxyqueuosine reductase family by comparative genomics. ACS Chem. Biol. 12 (2017) 844–851. [PMID: 28128549]

3. Li, Q., Zallot, R., MacTavish, B.S., Montoya, A., Payan, D.J., Hu, Y., Gerlt, J.A., Angerhofer, A., de Crecy-Lagard, V. and Bruner, S.D. Epoxyqueuosine reductase QueH in the biosynthetic pathway to tRNA queuosine is a unique metalloenzyme. Biochemistry 60 (2021) 3152-3161. [PMID: 34652139]

[EC created 2014]

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