The Enzyme Database

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Accepted name: preQ1 synthase
Reaction: 7-aminomethyl-7-carbaguanine + 2 NADP+ = 7-cyano-7-carbaguanine + 2 NADPH + 2 H+
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): YkvM; QueF; preQ0 reductase; preQ0 oxidoreductase; 7-cyano-7-deazaguanine reductase; queuine synthase (incorrect as queuine is not the product); queuine:NADP+ oxidoreductase (incorrect as queuine is not the product)
Systematic name: 7-aminomethyl-7-carbaguanine:NADP+ oxidoreductase
Comments: The reaction occurs in the reverse direction. This enzyme catalyses one of the early steps in the synthesis of queuosine (Q-tRNA), and is followed by the action of EC, tRNA-guanosine34 transglycosylase. Queuosine is found in the wobble position of tRNAGUN in Eukarya and Bacteria [2] and is thought to be involved in translational modulation. The enzyme is not a GTP cyclohydrolase, as was thought previously based on sequence-homology studies.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 1256460-80-6
1.  Van Lanen, S.G., Reader, J.S., Swairjo, M.A., de Crécy-Lagard, V., Lee, B. and Iwata-Reuyl, D. From cyclohydrolase to oxidoreductase: discovery of nitrile reductase activity in a common fold. Proc. Natl. Acad. Sci. USA 102 (2005) 4264–4269. [DOI] [PMID: 15767583]
2.  Yokoyama, S., Miyazawa, T., Iitaka, Y., Yamaizumi, Z., Kasai, H. and Nishimura, S. Three-dimensional structure of hyper-modified nucleoside Q located in the wobbling position of tRNA. Nature 282 (1979) 107–109. [PMID: 388227]
3.  Kuchino, Y., Kasai, H., Nihei, K. and Nishimura, S. Biosynthesis of the modified nucleoside Q in transfer RNA. Nucleic Acids Res. 3 (1976) 393–398. [DOI] [PMID: 1257053]
4.  Okada, N., Noguchi, S., Nishimura, S., Ohgi, T., Goto, T., Crain, P.F. and McCloskey, J.A. Structure determination of a nucleoside Q precursor isolated from E. coli tRNA: 7-(aminomethyl)-7-deazaguanosine. Nucleic Acids Res. 5 (1978) 2289–2296. [DOI] [PMID: 353740]
5.  Noguchi, S., Yamaizumi, Z., Ohgi, T., Goto, T., Nishimura, Y., Hirota, Y. and Nishimura, S. Isolation of Q nucleoside precursor present in tRNA of an E. coli mutant and its characterization as 7-(cyano)-7-deazaguanosine. Nucleic Acids Res. 5 (1978) 4215–4223. [DOI] [PMID: 364423]
6.  Swairjo, M.A., Reddy, R.R., Lee, B., Van Lanen, S.G., Brown, S., de Crécy-Lagard, V., Iwata-Reuyl, D. and Schimmel, P. Crystallization and preliminary X-ray characterization of the nitrile reductase QueF: a queuosine-biosynthesis enzyme. Acta Crystallogr. F Struct. Biol. Cryst. Commun. 61 (2005) 945–948. [DOI] [PMID: 16511203]
[EC created 2006]
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, 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]
Accepted name: S-adenosylmethionine:tRNA ribosyltransferase-isomerase
Reaction: S-adenosyl-L-methionine + 7-aminomethyl-7-carbaguanosine34 in tRNA = L-methionine + adenine + epoxyqueuosine34 in tRNA
For diagram of queuine biosynthesis, click here
Glossary: 7-aminomethyl-7-carbaguanine = preQ1 = 7-aminomethyl-7-deazaguanine
epoxyqueosine = oQ
Other name(s): QueA enzyme; queuosine biosynthesis protein QueA
Systematic name: S-adenosyl-L-methionine:7-aminomethyl-7-deazaguanosine ribosyltransferase (ribosyl isomerizing; L-methionine, adenine releasing)
Comments: The reaction is a combined transfer and isomerization of the ribose moiety of S-adenosyl-L-methionine to the modified guanosine base in the wobble position in tRNAs specific for Tyr, His, Asp or Asn. It is part of the queuosine biosynthesis pathway.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
1.  Slany, R.K., Bosl, M., Crain, P.F. and Kersten, H. A new function of S-adenosylmethionine: the ribosyl moiety of AdoMet is the precursor of the cyclopentenediol moiety of the tRNA wobble base queuine. Biochemistry 32 (1993) 7811–7817. [PMID: 8347586]
2.  Slany, R.K., Bosl, M. and Kersten, H. Transfer and isomerization of the ribose moiety of AdoMet during the biosynthesis of queuosine tRNAs, a new unique reaction catalyzed by the QueA protein from Escherichia coli. Biochimie 76 (1994) 389–393. [DOI] [PMID: 7849103]
3.  Kinzie, S.D., Thern, B. and Iwata-Reuyl, D. Mechanistic studies of the tRNA-modifying enzyme QueA: a chemical imperative for the use of AdoMet as a "ribosyl" donor. Org. Lett. 2 (2000) 1307–1310. [PMID: 10810734]
4.  Van Lanen, S.G. and Iwata-Reuyl, D. Kinetic mechanism of the tRNA-modifying enzyme S-adenosylmethionine:tRNA ribosyltransferase-isomerase (QueA). Biochemistry 42 (2003) 5312–5320. [DOI] [PMID: 12731872]
5.  Mathews, I., Schwarzenbacher, R., McMullan, D., Abdubek, P., Ambing, E., Axelrod, H., Biorac, T., Canaves, J.M., Chiu, H.J., Deacon, A.M., DiDonato, M., Elsliger, M.A., Godzik, A., Grittini, C., Grzechnik, S.K., Hale, J., Hampton, E., Han, G.W., Haugen, J., Hornsby, M., Jaroszewski, L., Klock, H.E., Koesema, E., Kreusch, A., Kuhn, P., Lesley, S.A., Levin, I., Miller, M.D., Moy, K., Nigoghossian, E., Ouyang, J., Paulsen, J., Quijano, K., Reyes, R., Spraggon, G., Stevens, R.C., van den Bedem, H., Velasquez, J., Vincent, J., White, A., Wolf, G., Xu, Q., Hodgson, K.O., Wooley, J. and Wilson, I.A. Crystal structure of S-adenosylmethionine:tRNA ribosyltransferase-isomerase (QueA) from Thermotoga maritima at 2.0 Å resolution reveals a new fold. Proteins 59 (2005) 869–874. [DOI] [PMID: 15822125]
6.  Grimm, C., Ficner, R., Sgraja, T., Haebel, P., Klebe, G. and Reuter, K. Crystal structure of Bacillus subtilis S-adenosylmethionine:tRNA ribosyltransferase-isomerase. Biochem. Biophys. Res. Commun. 351 (2006) 695–701. [DOI] [PMID: 17083917]
[EC created 2012]

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