Transport and processing of the precursors of mitochondrial carbamoyl phosphate synthetase I and ornithine transcarbamoylase

1984 ◽  
Vol 12 (3) ◽  
pp. 377-378 ◽  
Author(s):  
PHILIP P. COHEN
Keyword(s):  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Ornithine Transcarbamoylase

Arginine synthesis by hepatomas in vitro. I. The requirements for cell growth in medium containing ornithine in place of arginine and the isolation and characterization of variant hepatomas auxotrophic for arginine

1984 ◽  
Vol 68 (1) ◽  
pp. 285-303 ◽  
Author(s):  
S.J. Goss
Keyword(s):  
Cell Growth ◽  
The Other ◽  
Gene Products ◽  
Carbamoyl Phosphate Synthetase ◽  
Arginine Biosynthesis ◽  
Carbamoyl Phosphate ◽  
Isolation And Characterization ◽  
Ornithine Transcarbamoylase

Cell growth in ‘ornithine-medium’ requires the expression of two liver-specific genes, those for ornithine transcarbamoylase (OTC) and carbamoyl phosphate synthetase I (CPS-I). CPS-II appears unable to replace CPS-I in this system. The need for N-acetylglutamate (to activate CPS-I) can be met, at least in part, by providing it in the medium. The other gene products involved in arginine biosynthesis are probably all ubiquitous (i.e. not tissue-specific). In an attempt to study the factors responsible for the expression of liver-specific genes, variant hepatomas are isolated that have lost the ability to grow in ornithine-medium. Two classes of ‘orn-’ variants are identified: unstable variants that require dexamethasone for adequate CPS-I production, and ‘stable’ variants that have lost many liver-specific traits. Studies on one stable variant show that it can revert (though rarely), and that it regains its various liver-specific traits in a non-coordinate fashion.

scholarly journals Inhibition of ureagenesis by valproate in rat hepatocytes. Role of N-acetylglutamate and acetyl-CoA

1983 ◽  
Vol 216 (1) ◽  
pp. 233-236 ◽  
Author(s):  
F X Coude ◽  
G Grimber ◽  
P Parvy ◽  
D Rabier ◽  
F Petit
Keyword(s):  
Rat Hepatocytes ◽  
Urea Synthesis ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Acetyl Coa ◽  
Isolated Rat Hepatocytes ◽  
Cellular Concentration ◽  
Acetylglutamate Synthase ◽  
Ornithine Transcarbamoylase

Valproate (0.5-5 mM) strongly inhibited urea synthesis in isolated rat hepatocytes incubated with 10 mM-alanine and 3 mM-ornithine. Valproate at the same concentrations markedly decreased concentrations of N-acetylglutamate, an essential activator of carbamoyl-phosphate synthetase I (EC 6.3.4.16), in parallel with the inhibition of urea synthesis by valproate. This compound also lowered the cellular concentration of acetyl-CoA, a substrate of N-acetylglutamate synthase (EC 2.3.1.1); glutamate, aspartate and citrulline were similarly decreased. Valproate in a dose up to 2 mM did not significantly affect the cellular concentration of ATP and had no direct effect on N-acetylglutamate synthesis, carbamoyl-phosphate synthetase I and ornithine transcarbamoylase (EC 2.1.3.3) activities.

scholarly journals Pyrimidine nucleotide biosynthesis in Phaseolus aureus. Enzymic aspects of the control of carbamoyl phosphate synthesis and utilization

1972 ◽  
Vol 129 (3) ◽  
pp. 583-593 ◽  
Author(s):  
B. L. Ong ◽  
J. F. Jackson
Keyword(s):  
Inhibitory Effect ◽  
Aspartate Transcarbamoylase ◽  
Synthetase Activity ◽  
Carbamoyl Phosphate Synthetase ◽  
Phaseolus Aureus ◽  
Carbamoyl Phosphate ◽  
Purine Nucleotides ◽  
Nucleotide Biosynthesis ◽  
Pyrimidine Nucleotide ◽  
Ornithine Transcarbamoylase

1. Carbamoyl phosphate synthetase activity of Phaseolus aureus extracts was assayed by coupling it to the catalytic subunit of Escherichia coli aspartate transcarbamoylase and determining the [14C]carbamoylaspartate so formed. The stability of the activity was improved by the addition of ornithine and dimethyl sulphoxide to the extraction medium. 2. The synthetase activity was found to utilize either glutamine or ammonia as amino donor, the Michaelis constants being 0.17±0.03mm and 6.1±1.0mm respectively. N-Acetylglutamate did not significantly alter the rate with either substrate, and azaserine inhibited the reaction with both amino donors to the same extent. 3. Ornithine was shown to stimulate the activity, and to counteract inhibition by UMP. The purine nucleotides IMP and GMP enhanced carbamoyl phosphate formation, whereas AMP had an inhibitory effect. 4. The Michaelis constant for carbamoyl phosphate was determined in concentrated extracts for both aspartate transcarbamoylase and ornithine transcarbamoylase activities, and was 0.13±0.03mm and 1.58±0.16mm respectively. The ratio of the activities of these two enzymes, determined at near-saturating substrate concentrations, was 1:3 (aspartate transcarbamoylase/ornithine transcarbamoylase). 5. It is concluded that in this plant tissue there is one enzyme, carbamoyl phosphate synthetase, supplying carbamoyl phosphate to both the pyrimidine and arginine pathways, that the pyrimidine pathway claims most of the available carbamoyl phosphate (depending on the concentration of the nucleotide effectors) when this intermediate is present at low concentrations; and that when the carbamoyl phosphate concentration is increased, possibly by ornithine stimulation, a larger proportion can be taken up by the arginine pathway.

scholarly journals Product inhibition studies on bovine liver carbamoyl phosphate synthetase

1974 ◽  
Vol 141 (3) ◽  
pp. 817-824 ◽  
Author(s):  
Keith R. F. Elliott ◽  
Keith F. Tipton
Keyword(s):  
Inorganic Phosphate ◽  
Substrate Binding ◽  
Inorganic Ions ◽  
Bovine Liver ◽  
Product Inhibition ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Product Release ◽  
Proposed Model ◽  
Inhibition Studies

A study of the product-inhibition patterns of carbamoyl phosphate synthetase from bovine liver is reported. Inhibition by adenosine, AMP and inorganic ions is also reported. The results are in agreement with the previously proposed model in which the order of substrate binding is ATPMg, followed by HCO3−, ATPMg and NH4+. The order of product release on the basis of the reported results is carbamoyl phosphate, followed by ADPMg, ADPMg and inorganic phosphate.

Inactivation by acivicin of carbamoyl-phosphate synthetase II of human colon carcinoma

1985 ◽  
Vol 34 (1) ◽  
pp. 97-100 ◽  
Author(s):  
Judith S. Sebolt ◽  
Takashi Aoki ◽  
John N. Eble ◽  
John L Glover ◽  
George Weber
Keyword(s):  
Colon Carcinoma ◽  
Human Colon ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Human Colon Carcinoma

Spatial relationships among the active and allosteric sites of carbamoyl-phosphate synthetase

1985 ◽  
Vol 13 (2) ◽  
pp. 98-109 ◽  
Author(s):  
Philip G. Kasprzyk ◽  
Eric Whalen-Pederson ◽  
Paul M. Anderson ◽  
Joseph J. Villafranca
Keyword(s):  
Spatial Relationships ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Allosteric Sites
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