Reaction: (1) [tRNA]-guanine + queuine = [tRNA]-queuine + guanine
(2) [tRNA]-guanine + 7-aminomethyl-7-carbaguanine = [tRNA]-7-aminomethyl-7-carbaguanine + guanine
For diagram click here.
Glossary: preQ1 = 7-aminomethyl-7-carbaguanine
preQ0 = 7-cyano-7-carbaguanine
queuine = base Q = 22-amino-5-({[(1S,4S,5R)-4,5-dihydroxycyclopent-2-en-1-yl]amino}methyl)-1,7-dihydropyrrolo[3,2-e]pyrimidin-4-one
Other name(s): guanine insertion enzyme; tRNA transglycosylase; Q-insertase; queuine transfer ribonucleate ribosyltransferase; transfer ribonucleate glycosyltransferase; tRNA guanine transglycosidase; guanine, queuine-tRNA transglycosylase; queuine tRNA-ribosyltransferase; TGT; [tRNA]-guanine:queuine tRNA-D-ribosyltransferase; transfer ribonucleic acid guanine transglycosylase
Systematic name: tRNA-guanine:queuine tRNA-D-ribosyltransferase
Comments: In eukaryotes, queuine is incorporated into tRNA directly via a base-exchange reaction (replacing guanine) whereas in eubacteria, the queuine precursor preQ1 is incorporated and ultimately modified to queuine [4]. In eubacteria, preQ0 can also be incorporated into undermodified tRNATyr and tRNAAsn containing normal guanine instead of queuine in the first position of the anticodon [2]. This enzyme acts after EC 1.7.1.13, preQ1 synthase, in the queuine-biosynthesis pathway.
Links to other databases: BRENDA, EXPASY, KEGG, PDB, CAS registry number: 72162-89-1
References:
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 (1978) 9082-9087. [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 (1979) 3067-3073. [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 (1980) 395-400. [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 (2006) 617-625. [PMID: 16401090]