scholarly journals The human Rad9 checkpoint protein stimulates the carbamoyl phosphate synthetase activity of the multifunctional protein CAD

2004 ◽  
Vol 32 (15) ◽  
pp. 4524-4530 ◽  
Author(s):  
L. A. Lindsey-Boltz
Keyword(s):  
Synthetase Activity ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Multifunctional Protein ◽  
Checkpoint Protein ◽  
Human Rad9

scholarly journals Altered Nitrogen Balance and Decreased Urea Excretion in Male Rats Fed Cafeteria Diet Are Related to Arginine Availability

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
David Sabater ◽  
Silvia Agnelli ◽  
Sofía Arriarán ◽  
José-Antonio Fernández-López ◽  
María del Mar Romero ◽  
...  
Keyword(s):  
Amino Acid ◽  
Urea Cycle ◽  
Cafeteria Diet ◽  
Nitrogen Excretion ◽  
Male Rats ◽  
Synthetase Activity ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Urea Excretion ◽  
Dietary Nitrogen

Hyperlipidic diets limit glucose oxidation and favor amino acid preservation, hampering the elimination of excess dietary nitrogen and the catabolic utilization of amino acids. We analyzed whether reduced urea excretion was a consequence of higherNOx; (nitrite, nitrate, and other derivatives) availability caused by increased nitric oxide production in metabolic syndrome. Rats fed a cafeteria diet for 30 days had a higher intake and accumulation of amino acid nitrogen and lower urea excretion. There were no differences in plasma nitrate or nitrite.NOxand creatinine excretion accounted for only a small part of total nitrogen excretion. Rats fed a cafeteria diet had higher plasma levels of glutamine, serine, threonine, glycine, and ornithine when compared with controls, whereas arginine was lower. Liver carbamoyl-phosphate synthetase I activity was higher in cafeteria diet-fed rats, but arginase I was lower. The high carbamoyl-phosphate synthetase activity and ornithine levels suggest activation of the urea cycle in cafeteria diet-fed rats, but low arginine levels point to a block in the urea cycle between ornithine and arginine, thereby preventing the elimination of excess nitrogen as urea. The ultimate consequence of this paradoxical block in the urea cycle seems to be the limitation of arginine production and/or availability.

scholarly journals Altered enzyme activities and citrulline synthesis in liver mitochondria from ornithine carbamoyltransferase-deficient sparse-furash mice

1989 ◽  
Vol 257 (1) ◽  
pp. 251-257 ◽  
Author(s):  
N S Cohen ◽  
C W Cheung ◽  
L Raijman
Keyword(s):  
Protein Interactions ◽  
Mitochondrial Protein ◽  
Normal Liver ◽  
Liver Mitochondria ◽  
Synthetase Activity ◽  
Single Mutation ◽  
Ornithine Carbamoyltransferase ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Citrulline Synthesis

Male mice carrying the spfash mutation have 5-10% of the normal activity of ornithine carbamoyltransferase, yet are only slightly hyperammonaemic and develop quite well. A study of liver mitochondria from normal and spfash males showed that they differ in important ways. (1) The spfash liver contains about 33% more mitochondrial protein per g than does normal liver. (2) The specific activities of carbamoyl-phosphate synthetase (ammonia) and glutamate dehydrogenase are about 15% lower than normal in mitochondria from spfash mice, whereas those of beta-hydroxybutyrate dehydrogenase and cytochrome oxidase are 22% higher and 30% lower respectively. (3) In the presence of 10 mM-ornithine and the substrates for carbamoyl phosphate synthesis, coupled and uncoupled mitochondria from spfash mice synthesize citrulline at unexpectedly high rates, about 25 and 44 nmol/min per mg respectively. Though these are somewhat lower than the corresponding rates obtained with normal mitochondria, the difference does not arise from the deficiency in ornithine carbamoyltransferase, but from the lower carbamoyl-phosphate synthetase activity of the mutant mitochondria. (4) At lower external [ornithine] (less than 2 mM), a smaller fraction of the carbamoyl phosphate synthesized is converted into citrulline in spfash than in normal mitochondria. These studies show that what appears to be a single mutation brings about major adaptations in the mitochondrial component of liver. In addition, they clarify the role of ornithine transport and of protein-protein interactions in citrulline synthesis in normal mitochondria.

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 Organization of a multifunctional protein in pyrimidine biosynthesis. A domain hypersensitive to proteolysis

1984 ◽  
Vol 217 (2) ◽  
pp. 435-440 ◽  
Author(s):  
P C Rumsby ◽  
P C Campbell ◽  
L A Niswander ◽  
J N Davidson
Keyword(s):  
Pyrimidine Biosynthesis ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Multifunctional Protein ◽  
Aggregation Site ◽  
Aspartate Carbamoyltransferase ◽  
Low Concentrations ◽  
Proteinase A

When the multifunctional protein that catalyses the first three steps of pyrimidine biosynthesis in hamster cells is treated with staphylococcal V8 proteinase, a single cleavage takes place. The activities of carbamoyl-phosphate synthetase (EC 6.3.5.5), aspartate carbamoyltransferase (EC 2.1.3.2) and dihydro-orotase (EC 3.5.2.3) and the allosteric inhibition by UTP are unaffected. One fragment, of Mr 182000, has the first and third enzyme activities, whereas the other fragment, of Mr 42000, has aspartate carbamoyltransferase activity and an aggregation site. A similar small fragment is observed in protein digested with low concentrations of trypsin. A similar large fragment is seen after digestion with trypsin and as the predominating form of this protein in certain mutants defective in pyrimidine biosynthesis. These results indicate that a region located adjacent to the aspartate carbamoyltransferase domain is hypersensitive to proteinase action in vitro and may also be sensitive to proteolysis in vivo.

scholarly journals Pyrimidine Biosynthetic Enzyme CAD: Its Function, Regulation, and Diagnostic Potential

2021 ◽  
Vol 22 (19) ◽  
pp. 10253
Author(s):  
Guanya Li ◽  
Dunhui Li ◽  
Tao Wang ◽  
Shanping He
Keyword(s):  
Metabolic Diseases ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Nucleotide Synthesis ◽  
Multifunctional Protein ◽  
The Past ◽  
Pyrimidine Nucleotide ◽  
Diagnostic Potential ◽  
Active Intermediates

CAD (Carbamoyl-phosphate synthetase 2, Aspartate transcarbamoylase, and Dihydroorotase) is a multifunctional protein that participates in the initial three speed-limiting steps of pyrimidine nucleotide synthesis. Over the past two decades, extensive investigations have been conducted to unmask CAD as a central player for the synthesis of nucleic acids, active intermediates, and cell membranes. Meanwhile, the important role of CAD in various physiopathological processes has also been emphasized. Deregulation of CAD-related pathways or CAD mutations cause cancer, neurological disorders, and inherited metabolic diseases. Here, we review the structure, function, and regulation of CAD in mammalian physiology as well as human diseases, and provide insights into the potential to target CAD in future clinical applications.

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