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Literature summary extracted from

  • Meister, A.
    Mechanism and regulation of the glutamine-dependent carbamyl phosphate synthetase of Escherichia coli (1989), Adv. Enzymol. Relat. Areas Mol. Biol., 62, 315-374.
    View publication on PubMed

Activating Compound

EC Number Activating Compound Comment Organism Structure
6.3.5.5 N-acetylglutamate carbamoyl-phosphate synthase III: requirement for N-acetylglutamate Squalus acanthias
6.3.5.5 N-acetylglutamate carbamoyl-phosphate synthase II: no requirement for N-acetylglutamate Mammalia
6.3.5.5 N-acetylglutamate carbamoyl-phosphate synthase II: no requirement for N-acetylglutamate Escherichia coli
6.3.5.5 NEM 250fold activation of glutaminase activity. Irreversible inactivation of synthetase activity Escherichia coli
6.3.5.5 Orn activates Escherichia coli
6.3.5.5 thiol required for Gln-dependent activity Escherichia coli

Cloned(Commentary)

EC Number Cloned (Comment) Organism
6.3.5.5
-
Escherichia coli

Protein Variants

EC Number Protein Variants Comment Organism
6.3.5.5 C269G Cys269Gly and Cys269Ser mutants bind significant amounts of Gln but do not hydrolyze Gln. The mutants are able to catalyze carbamoyl-phosphate formation with NH4+ as nitrogen donor, at a rate equal to that of the wild type enzyme. The mutant enzyme catalyzes ATP synthesis from ADP and carbamoyl phosphate at the usual rates. Substantial increase in bicarbonate-dependent ATPase Escherichia coli
6.3.5.5 C269S Cys269Gly and Cys269Ser mutants bind significant amounts of Gln but do not hydrolyze Gln. The mutants are able to catalyze carbamoyl-phosphate formation with NH4+ as nitrogen donor, at a rate equal to that of the wild type enzyme. The mutant enzyme catalyzes ATP synthesis from ADP and carbamoyl phosphate at the usual rates. Substantial increase in bicarbonate-dependent ATPase Escherichia coli

General Stability

EC Number General Stability Organism
6.3.5.5 treatment with 1 M potassium thiocyanate results in reversible dissociation into its subunits which retain catalytic activity Escherichia coli

Inhibitors

EC Number Inhibitors Comment Organism Structure
6.3.5.5 Alkyl hydrazines inhibits Gln-dependent activity, but not NH4+-dependent activity Escherichia coli
6.3.5.5 H2O2 0.2 mM, inhibits Gln-dependent activity. No effect on the activity with NH4+ in carbamoyl-phosphate synthase reaction Escherichia coli
6.3.5.5 hydroxylamine inhibits Gln-dependent activity, but not NH4+-dependent activity; the inhibitory effect is much greater at pH 9 than at pH 6 Escherichia coli
6.3.5.5 L-2-Amino-4-oxo-5-chloropentanoate selective inactivation of Gln-dependent activity Escherichia coli
6.3.5.5 NEM irreversible inactivation of synthetase activity. Increase of glutaminase activity Escherichia coli
6.3.5.5 potassium cyanate inhibits Gln-dependent activity, but not NH4+-dependent activity Escherichia coli
6.3.5.5 UMP
-
Escherichia coli

KM Value [mM]

EC Number KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
6.3.5.5 0.38
-
L-Gln
-
Escherichia coli
6.3.5.5 93
-
NH4+
-
Escherichia coli

Localization

EC Number Localization Comment Organism GeneOntology No. Textmining
6.3.5.5 cytosol
-
Mammalia 5829
-

Metals/Ions

EC Number Metals/Ions Comment Organism Structure
6.3.5.5 K+ required for maximal activity Escherichia coli
6.3.5.5 Mg2+ free Mg2+ is required in addition to MgATP2- Escherichia coli
6.3.5.5 Mn2+ maximal activity at concentration of Mn2+ approximately equal to the ATP concentration Escherichia coli
6.3.5.5 NH4+ can replace K+ in activation Escherichia coli

Molecular Weight [Da]

EC Number Molecular Weight [Da] Molecular Weight Maximum [Da] Comment Organism
6.3.5.5 40000
-
1 * 40000, subunit contains the binding site for glutamine, + 1 * 133000, subunit contains the binding sites for NH4+, HCO3-, ATP, and the allosteric effectors. The light and heavy subunits are encoded by the genetically linked car A and car B genes, respectively Escherichia coli
6.3.5.5 133000
-
1 * 40000, subunit contains the binding site for glutamine, + 1 * 133000, subunit contains the binding sites for NH4+, HCO3-, ATP, and the allosteric effectors. The light and heavy subunits are encoded by the genetically linked car A and car B genes, respectively Escherichia coli

Natural Substrates/ Products (Substrates)

EC Number Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
6.3.5.5 ATP + L-Gln + HCO3- Elasmobranchii functions in the synthesis of urea used in osmoregulation ?
-
?
6.3.5.5 ATP + L-Gln + HCO3- Mammalia catalyzes the first step of de novo pyrimidine biosynthesis ?
-
?

Organism

EC Number Organism UniProt Comment Textmining
6.3.5.5 Agaricus bisporus
-
-
-
6.3.5.5 Elasmobranchii
-
-
-
6.3.5.5 Escherichia coli
-
-
-
6.3.5.5 Fresh-water teleost
-
-
-
6.3.5.5 Mammalia
-
-
-
6.3.5.5 Squalus acanthias
-
-
-

Reaction

EC Number Reaction Comment Organism Reaction ID
6.3.5.5 2 ATP + L-glutamine + hydrogencarbonate + H2O = 2 ADP + phosphate + L-glutamate + carbamoyl phosphate mechanism, formation of enzyme-bound carboxy phosphate Escherichia coli

Substrates and Products (Substrate)

EC Number Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
6.3.5.5 2 ATP + L-Gln + HCO3-
-
Mammalia 2 ADP + phosphate + L-Glu + carbamoyl phosphate
-
?
6.3.5.5 2 ATP + L-Gln + HCO3-
-
Squalus acanthias 2 ADP + phosphate + L-Glu + carbamoyl phosphate
-
?
6.3.5.5 2 ATP + L-Gln + HCO3-
-
Elasmobranchii 2 ADP + phosphate + L-Glu + carbamoyl phosphate
-
?
6.3.5.5 2 ATP + L-Gln + HCO3-
-
Fresh-water teleost 2 ADP + phosphate + L-Glu + carbamoyl phosphate
-
?
6.3.5.5 2 ATP + L-Gln + HCO3-
-
Agaricus bisporus 2 ADP + phosphate + L-Glu + carbamoyl phosphate
-
?
6.3.5.5 2 ATP + L-Gln + HCO3- overall reaction is irreversible Escherichia coli 2 ADP + phosphate + L-Glu + carbamoyl phosphate
-
?
6.3.5.5 2 ATP + NH4+ + HCO3-
-
Escherichia coli 2 ADP + phosphate + carbamoyl phosphate
-
?
6.3.5.5 ATP + L-Gln + HCO3- functions in the synthesis of urea used in osmoregulation Elasmobranchii ?
-
?
6.3.5.5 ATP + L-Gln + HCO3- catalyzes the first step of de novo pyrimidine biosynthesis Mammalia ?
-
?

Subunits

EC Number Subunits Comment Organism
6.3.5.5 dimer 1 * 40000, subunit contains the binding site for glutamine, + 1 * 133000, subunit contains the binding sites for NH4+, HCO3-, ATP, and the allosteric effectors. The light and heavy subunits are encoded by the genetically linked car A and car B genes, respectively Escherichia coli
6.3.5.5 More
-
Mammalia
6.3.5.5 More enzyme can exist in different monomer conformations and states of association Escherichia coli

pH Optimum

EC Number pH Optimum Minimum pH Optimum Maximum Comment Organism
6.3.5.5 4.2
-
and a second optimum at pH 9.5, glutaminase activity Escherichia coli
6.3.5.5 7.8 8.2
-
Escherichia coli
6.3.5.5 9.5
-
and a second optimum at pH 4.2, glutaminase activity Escherichia coli

Cofactor

EC Number Cofactor Comment Organism Structure
6.3.5.5 IMP stimulates Escherichia coli