EC - TRNA-guanine34 transglycosylase

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IntEnz Enzyme Nomenclature


Accepted name:
tRNA-guanine34 transglycosylase
Other names:
Q-insertase [ambiguous]
guanine insertion enzyme [ambiguous]
guanine, queuine-tRNA transglycosylase
queuine transfer ribonucleate ribosyltransferase
tRNA guanine34 transglycosidase
tRNA transglycosylase [ambiguous]
queuine tRNA-ribosyltransferase
transfer ribonucleate glycosyltransferase [ambiguous]
[tRNA]-guanine34:queuine tRNA-D-ribosyltransferase
transfer ribonucleic acid guanine34 transglycosylase
queuine34 transfer ribonucleate ribosyltransferase
Systematic name:
tRNA-guanine34:queuine tRNA-D-ribosyltransferase



Certain prokaryotic and eukaryotic tRNAs contain the modified base queuine at position 34. In eukaryotes queuine is salvaged from food and incorporated into tRNA directly via a base-exchange reaction, replacing guanine. In eubacteria, which produce queuine de novo, the enzyme catalyses the exchange of guanine with the queuine precursor preQ1, which is ultimately modified to queuine [4,5]. The eubacterial enzyme can also use an earlier intermediate, preQ0, to replace guanine in unmodified tRNATyr and tRNAAsn [2]. This enzyme acts after EC, preQ1 synthase, in the queuine-biosynthesis pathway.

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , DIAGRAM , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
Gene Ontology: GO:0008479
CAS Registry Number: 72162-89-1
UniProtKB/Swiss-Prot: (473) [show] [UniProt]


  1. Howes, N.K. and Farkas, W.R.
    Studies with a homogeneous enzyme from rabbit erythrocytes catalyzing the insertion of guanine into tRNA.
    J. Biol. Chem. 253: 9082-9087 (1978). [PMID: 721832]
  2. Okada, N., Noguchi, S., Kasai, H., Shindo-Okada, N., Ohgi, T., Goto, T. and Nishimura, S.
    Novel mechanism of post-transcriptional modification of tRNA. Insertion of bases of Q precursors into tRNA by a specific tRNA transglycosylase reaction.
    J. Biol. Chem. 254: 3067-3073 (1979). [PMID: 372186]
  3. Shindo-Okada, N., Okada, N., Ohgi, T., Goto, T. and Nishimura, S.
    Transfer ribonucleic acid guanine transglycosylase isolated from rat liver.
    Biochemistry 19: 395-400 (1980). [PMID: 6986171]
  4. Todorov, K.A. and Garcia, G.A.
    Role of aspartate 143 in Escherichia coli tRNA-guanine transglycosylase: alteration of heterocyclic substrate specificity.
    Biochemistry 45: 617-625 (2006). [PMID: 16401090]
  5. Boland, C., Hayes, P., Santa-Maria, I., Nishimura, S., Kelly, V. P.
    Queuosine formation in eukaryotic tRNA occurs via a mitochondria-localized heteromeric transglycosylase.
    J. Biol. Chem. 284: 18218-18227 (2009). [PMID: 19414587]

[EC created 1984, modified 2007, modified 2012]