The Enzyme Database

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Accepted name: tRNA-guanosine34 preQ1 transglycosylase
Reaction: guanine34 in tRNA + 7-aminomethyl-7-carbaguanine = 7-aminomethyl-7-carbaguanine34 in tRNA + guanine
For diagram of queuine biosynthesis, click here
Glossary: 7-aminomethyl-7-carbaguanine = preQ1 = 7-aminomethyl-7-deazaguanine
7-cyano-7-carbaguanine = preQ0 = 7-cyano-7-deazaguanine
Other name(s): guanine insertion enzyme (ambiguous); tRNA transglycosylase (ambiguous); Q-insertase (ambiguous); transfer ribonucleate glycosyltransferase (ambiguous); tRNA guanine34 transglycosidase (ambiguous); TGT (ambiguous); transfer ribonucleic acid guanine34 transglycosylase (ambiguous)
Systematic name: tRNA-guanosine34:7-aminomethyl-7-deazaguanine tRNA-D-ribosyltransferase
Comments: Certain prokaryotic and eukaryotic tRNAs contain the modified base queuine at position 34. In eubacteria, which produce queuine de novo, the enzyme catalyses the exchange of guanine with the queuine precursor preQ1, which is ultimately modified to queuosine [5]. The enzyme can also use an earlier intermediate, preQ0, to replace guanine in unmodified tRNATyr and tRNAAsn [1]. This enzyme acts after EC, preQ1 synthase, in the queuine-biosynthesis pathway. cf. EC, tRNA-guanosine34 queuine transglycosylase.
Links to other databases: BRENDA, EXPASY, Gene, KEGG, MetaCyc, PDB, CAS registry number: 72162-89-1
1.  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 (1979) 3067–3073. [PMID: 372186]
2.  Noguchi, S., Nishimura, Y., Hirota, Y. and Nishimura, S. Isolation and characterization of an Escherichia coli mutant lacking tRNA-guanine transglycosylase. Function and biosynthesis of queuosine in tRNA. J. Biol. Chem. 257 (1982) 6544–6550. [PMID: 6804468]
3.  Chong, S., Curnow, A.W., Huston, T.J. and Garcia, G.A. tRNA-guanine transglycosylase from Escherichia coli is a zinc metalloprotein. Site-directed mutagenesis studies to identify the zinc ligands. Biochemistry 34 (1995) 3694–3701. [DOI] [PMID: 7893665]
4.  Goodenough-Lashua, D.M. and Garcia, G.A. tRNA-guanine transglycosylase from E. coli: a ping-pong kinetic mechanism is consistent with nucleophilic catalysis. Bioorg. Chem. 31 (2003) 331–344. [DOI] [PMID: 12877882]
5.  Todorov, K.A. and Garcia, G.A. Role of aspartate 143 in Escherichia coli tRNA-guanine transglycosylase: alteration of heterocyclic substrate specificity. Biochemistry 45 (2006) 617–625. [DOI] [PMID: 16401090]
[EC created 1984, modified 2007, modified 2012, modified 2020]

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