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Enzyme Nomenclature
Information on EC 6.3.4.20 - 7-cyano-7-deazaguanine synthase
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6.3.4.20 7-cyano-7-deazaguanine synthaseIUBMB Comments
Binds Zn2+. The reaction is part of the biosynthesis pathway of queuosine.
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The enzyme appears in viruses and cellular organisms
Reaction Schemes
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SYNONYM 
ORGANISM
UNIPROT
COMMENTARY 
LITERATURE
7-cyano-7-carbaguanine synthase
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preQ0 synthase
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queC
queC
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REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
7-carboxy-7-carbaguanine + NH3 + ATP = 7-cyano-7-carbaguanine + ADP + phosphate + H2O
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PATHWAY SOURCE
PATHWAYS
BRENDA
KEGG
MetaCyc
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SYSTEMATIC NAME
IUBMB Comments
7-carboxy-7-carbaguanine:ammonia ligase (ADP-forming)
Binds Zn2+. The reaction is part of the biosynthesis pathway of queuosine.
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CAS REGISTRY NUMBER
COMMENTARY
1256460-80-6
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SUBSTRATE
PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
7-carboxy-7-carbaguanine + NH3 + ATP
7-cyano-7-carbaguanine + ADP + phosphate + H2O
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?
7-carboxy-7-carbaguanine + NH3 + ATP
7-cyano-7-carbaguanine + ADP + phosphate + H2O
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dependent conversion of a carboxylic acid to a nitrile
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?
7-carboxy-7-carbaguanine + NH3 + ATP
7-cyano-7-carbaguanine + AMP + diphosphate + H2O
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?
7-carboxy-7-carbaguanine + NH3 + ATP
7-cyano-7-carbaguanine + AMP + diphosphate + H2O
the enzyme is involved in biosynthetic pathways towards deazapurine-containing compounds
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?
7-carboxy-7-carbaguanine + NH3 + ATP
7-cyano-7-carbaguanine + AMP + diphosphate + H2O
strict substrate specificity for 7-carboxy-7-carbaguanine. No ADP or phosphate is detected as product
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?
7-carboxy-7-carbaguanine + NH3 + ATP
7-cyano-7-carbaguanine + AMP + diphosphate + H2O
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?
7-carboxy-7-carbaguanine + NH3 + ATP
7-cyano-7-carbaguanine + AMP + diphosphate + H2O
the enzyme is involved in biosynthetic pathways towards deazapurine-containing compounds
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-
?
7-carboxy-7-carbaguanine + NH3 + ATP
7-cyano-7-carbaguanine + AMP + diphosphate + H2O
strict substrate specificity for 7-carboxy-7-carbaguanine. No ADP or phosphate is detected as product
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?
7-carboxy-7-carbaguanine + NH3 + ATP
7-cyano-7-carbaguanine + AMP + diphosphate + H2O
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?
7-carboxy-7-carbaguanine + NH3 + ATP
7-cyano-7-carbaguanine + AMP + diphosphate + H2O
the enzyme is involved in biosynthetic pathways towards deazapurine-containing compounds
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-
?
7-carboxy-7-carbaguanine + NH3 + ATP
7-cyano-7-carbaguanine + AMP + diphosphate + H2O
strict substrate specificity for 7-carboxy-7-carbaguanine. No ADP or phosphate is detected as product
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?
additional information
?
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no substrates: indole-3-carboxylic acid, cinnamic acid, pyrrole-2-carboxylic acid, benzoic acid, pyridine-2-carboxylic acid, 3-phenylpropionic acid, 2-methyl-4-oxo-4,5,6,7-tetrahydro-1H-indole-3-carboxylic acid, pyrrole-3-carboxylic acid, rac-mandelic acid, pyrazinecarboxylic acid
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?
additional information
?
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no substrates: indole-3-carboxylic acid, cinnamic acid, pyrrole-2-carboxylic acid, benzoic acid, pyridine-2-carboxylic acid, 3-phenylpropionic acid, 2-methyl-4-oxo-4,5,6,7-tetrahydro-1H-indole-3-carboxylic acid, pyrrole-3-carboxylic acid, rac-mandelic acid, pyrazinecarboxylic acid
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?
additional information
?
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no substrates: indole-3-carboxylic acid, cinnamic acid, pyrrole-2-carboxylic acid, benzoic acid, pyridine-2-carboxylic acid, 3-phenylpropionic acid, 2-methyl-4-oxo-4,5,6,7-tetrahydro-1H-indole-3-carboxylic acid, pyrrole-3-carboxylic acid, rac-mandelic acid, pyrazinecarboxylic acid
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?
additional information
?
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no substrates: indole-3-carboxylic acid, cinnamic acid, pyrrole-2-carboxylic acid, benzoic acid, pyridine-2-carboxylic acid, 3-phenylpropionic acid, 2-methyl-4-oxo-4,5,6,7-tetrahydro-1H-indole-3-carboxylic acid, pyrrole-3-carboxylic acid, rac-mandelic acid, pyrazinecarboxylic acid
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?
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NATURAL SUBSTRATE
NATURAL PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
7-carboxy-7-carbaguanine + NH3 + ATP
7-cyano-7-carbaguanine + ADP + phosphate + H2O
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?
7-carboxy-7-carbaguanine + NH3 + ATP
7-cyano-7-carbaguanine + AMP + diphosphate + H2O
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-
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?
7-carboxy-7-carbaguanine + NH3 + ATP
7-cyano-7-carbaguanine + AMP + diphosphate + H2O
the enzyme is involved in biosynthetic pathways towards deazapurine-containing compounds
-
-
?
7-carboxy-7-carbaguanine + NH3 + ATP
7-cyano-7-carbaguanine + AMP + diphosphate + H2O
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-
-
?
7-carboxy-7-carbaguanine + NH3 + ATP
7-cyano-7-carbaguanine + AMP + diphosphate + H2O
the enzyme is involved in biosynthetic pathways towards deazapurine-containing compounds
-
-
?
7-carboxy-7-carbaguanine + NH3 + ATP
7-cyano-7-carbaguanine + AMP + diphosphate + H2O
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-
-
?
7-carboxy-7-carbaguanine + NH3 + ATP
7-cyano-7-carbaguanine + AMP + diphosphate + H2O
the enzyme is involved in biosynthetic pathways towards deazapurine-containing compounds
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-
?
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COFACTOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
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METALS and IONS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
Mg2+
Zn2+
Zn2+
coordination of a zinc ion by the conserved C(x)8CxxCxxC motif in QueC, binding structure, overview
Zn2+
Zn2+ ion seems to be of mainly structural importance
Zn2+
the enzyme harbors Zn2+ and Mg2+ ions, coordinated by a cysteine-rich binding motive
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pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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pH RANGE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
8 - 10
pH 8.0: about 70% of maximal activity, pH 10.0: about 70% of maximal activity
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TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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pI VALUE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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ORGANISM
COMMENTARY
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
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GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
evolution
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the enzyme belongs to GAT-QueC, a two-domain family with an N-terminal glutamine amidotransferase class-II domain fused to a domain homologous to QueC, the enzyme that produces preQ0. Phylogenetic distribution of aTGT, ArcS, GAT-QueC, and QueF-like in the two archaeal phyla, overview. Most crenarchaeal genomes encode a fused GAT-QueC protein or a QueF-like protein
malfunction
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the expression of QueC from a plasmid-borne copy confers a Q+ phenotype to enzyme-deficient mutant strain Escherichia coli B105
metabolism
physiological function
metabolism
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the metabolic pathway includes the conversion of the biosynthetic intermediate, 6-carboxy-5,6,7,8-tetrahydropterin, to intermediate, 7-carboxy-7-deazaguanine, CDG, by an unusual transformation catalyzed by QueE, a member of the radical SAM enzyme superfamily. The carboxylate moiety on CDG is converted subsequently to a nitrile to yield preQ0 by QueC in an ATP-dependent reaction, in which ammonia serves as the nitrogen source. CDG may be the central precursor to all deazapurines, biosynthesis of deazapurine containing compounds in nature incorporates H2NTP, CPH4 and CDG as common intermediates
metabolism
the products of four genes, queC, queD, queE, and queF, are involved in preQ1 biosynthesis with GTP as the starting material. preQ1 is transformed to Q in tRNA
metabolism
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the queC (ybaX) gene product functions in the initial step of queuosine biosynthetic pathway in Escherichia coli, queuosine incorporation in tRNAs, overview
metabolism
the enzyme is involved in biosynthetic pathways towards deazapurine-containing compounds
metabolism
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the enzyme is involved in biosynthetic pathways towards deazapurine-containing compounds
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metabolism
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the enzyme is involved in biosynthetic pathways towards deazapurine-containing compounds
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physiological function
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involvement of QueC at a step leading to production of preQ0, intermediate in the pathway that utilizes GTP as the starting molecule to produce queuosine, overview
physiological function
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the enzyme QueC produces the G+ precursor, 7-cyano-7-deazaguanine, i.e. preQ0, which is inserted into tRNA by tRNA-guanine transglycosylase before conversion into G+ by archaeosine synthase, ArcS. Gat-QueC and QueF-like families can compensate for lack of ArcS, overview
Show AA Sequence and Transmembrane Helices (21673 entries)
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SUBUNIT
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
dimer or tetramer
the biologically relevant unit is likely to be a QueC homodimer, crystal structure. Monomer structure, overview. The Rossmann fold of the N-terminal part of QueC, in combination with the C-terminal zinc-binding motif, forms a cavity in QueC of substantial size, which is likely to be the location of substrate binding
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CRYSTALLIZATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
purified QueC, vapor diffusion method, 10 mg/ml protein is mixed with crystallization solution containing 25% PEG 6000, 100 mM NaCl, 10 mM 1,6 hexanediol, and 100 mM MES, pH 5.5, 1 week, X-ray diffraction structure determination and analysis at 2.95 A resolution
molecular modeling of QueC-AMP complex. Residues Q39, T119, R97, and N98 are most likely involved in ATP binding. CDG binding likely involves residues Y129 or Y187 for pi-stacking of the CDG substrate, and D125 or D131 in binding the primary and secondary amines of the substrate pyrimidine
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PROTEIN VARIANTS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
additional information
additional information
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in vitro preparation of the deazapurine nucleoside, preQ0, by the successive action of the four involved enzymes, i.e. Escherichia coli QueD, Bacillus subtilis QueE and QueC, and Streptomyces rimosus ToyM, cloning and expression in Escherichia coli strain BL21(DE3), overview
additional information
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the expression of QueC from a plasmid-borne copy confers a Q+ phenotype to enzyme-deficient mutant strain Escherichia coli B105, mapping of the transposon insertion site, overview. Generation of a knockout of queC in Escherichia coli strain JE10651, a queA mutant
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TEMPERATURE STABILITY
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
78.5
melting temperature in presence of 7-carboxy-7-carbaguanine
82
82
melting temperature, in the presence of ATP and substrate
82
melting temperature in presence of ATP and 7-carboxy-7-carbaguanine
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PURIFICATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
recombinant His-tagged QueC from Escherichia coli strain BL21(DE3) by nickel affinity chromatography and gel filtration
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recombinant QueC from Escherichia coli strain BL21(DE3) by anion exchange chromatography, hydrophobic interaction chromatography, and another different step of anion exchange chromatography, followed by gel filtration
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CLONED (Commentary)
ORGANISM
UNIPROT
LITERATURE
cloning of His-tagged QueC and expression in Escherichia coli strain BL21(DE3)
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expressed at high level in Escherichia coli, and the protein is expressed with an N-terminal His tag-target protein
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REF.
AUTHORS
TITLE
JOURNAL
VOL.
PAGES
YEAR
ORGANISM (UNIPROT)
PUBMED ID
SOURCE
Phillips, G.; Swairjo, M.A.; Gaston, K.W.; Bailly, M.; Limbach, P.A.; Iwata-Reuyl, D.; de Crecy-Lagard, V.
Diversity of archaeosine synthesis in crenarchaeota
ACS Chem. Biol.
7
300-305
2012
Crenarchaeota
brenda
McCarty, R.M.; Somogyi, A.; Lin, G.; Jacobsen, N.E.; Bandarian, V.
The deazapurine biosynthetic pathway revealed: in vitro enzymatic synthesis of PreQ(0) from guanosine 5-triphosphate in four steps
Biochemistry
48
3847-3852
2009
Bacillus subtilis
brenda
Gaur, R.; Varshney, U.
Genetic analysis identifies a function for the queC (ybaX) gene product at an initial step in the queuosine biosynthetic pathway in Escherichia coli
J. Bacteriol.
187
6893-6901
2005
Escherichia coli
brenda
Cicmil, N.; Huang, R.
Crystal structure of QueC from Bacillus subtilis: an enzyme involved in preQ1 biosynthesis
Proteins
72
1084-1088
2008
Bacillus subtilis (O31675)
brenda
Winkler, M.; Dokulil, K.; Weber, H.; Pavkov-Keller, T.; Wilding, B.
The nitrile-forming enzyme 7-cyano-7-deazaguanine synthase from Geobacillus kaustophilus A reverse nitrilase?
ChemBioChem
16
2373-2378
2015
Geobacillus kaustophilus (A0A0N9HMW6), Geobacillus kaustophilus, Geobacillus kaustophilus DSM-7263 (A0A0N9HMW6), Geobacillus kaustophilus NBRC 102445 (A0A0N9HMW6)
brenda
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