scholarly journals The regulation of carbamoyl phosphate synthase activity in rat liver mitochondria

1976 ◽  
Vol 154 (2) ◽  
pp. 415-421 ◽  
Author(s):  
J D. McGivan ◽  
N M. Bradford ◽  
J Mendes-Mourão
Keyword(s):  
Protein Content ◽  
Nitrogen Source ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Urea Synthesis ◽  
Carbamoyl Phosphate ◽  
Citrulline Synthesis ◽  
Ornithine Transcarbamoylase ◽  
Phosphate Synthase

The rate at which isolated rat liver mitochondria synthesized citrulline with NH4C1 as nitrogen source was markedly dependent on the protein content of the diet. 2. Citrulline synthesis was not rate-limited by substrate concentration, substrate transport or ornithine transcarbamoylase activity under the conditions used. 3. The intramitochondrial content of an activator of carbamoyl phosphate synthase, assumed to be N-acetyl-glutamate, varied markedly with dietary protein content. The variation in the concentration of this activator was sufficient to account for the observed variation in the rates of citrulline synthesis if this synthesis were rate-limited by the activity of carbamoyl phosphate synthase. 4. The rates of urea formation from NH4Cl as nitrogen source in isolated liver cells showed variations in response to diet that closely paralleled the variations in the rates of citrulline synthesis observed in isolated mitochondria. 5. These results are consistent with the postulate that when NH4Cl plus ornithine are present in an excess, the rate of urea synthesis is regulated at the level of carbamoyl phosphate synthase activity.

scholarly journals Effect of pent-4-enoic acid, propionic acid and other short-chain fatty acids on citrulline synthesis in rat liver mitochondria

1976 ◽  
Vol 156 (2) ◽  
pp. 301-307 ◽  
Author(s):  
A M Glasgow ◽  
H P Chase
Keyword(s):  
Fatty Acids ◽  
Propionic Acid ◽  
Rat Liver ◽  
Short Chain Fatty Acids ◽  
Liver Mitochondria ◽  
Short Chain ◽  
Enoic Acid ◽  
Rat Liver Mitochondria ◽  
Carbamoyl Phosphate ◽  
Citrulline Synthesis

19 The effect of pent-4-enoic acid, propionic acid and several other short-chain fatty acids on citrulline synthesis in rat liver mitochondria was studied. 2. Pent-4-enoate at 1 mM inhibited mitochondrial citulline synthesis by about 80-90%. It is concluded that pent-4-enoate inhibits citrulline synthesis by interfering with some aspect of mitochondrial energy metabolism. This results in impairment of mitochondrial ornithine uptake or depletion of mitochondrial ATP, which, in turn, impairs carbamoyl phosphate synthesis or both. Evidence in support of this conclusion includes: pent-4-enoate has no effect on citrulline synthesis supported by succinate or exogenous ATP; pent-4-enoate lowers the medium plus mitochondrial ATP concentration; finally, when glutamate is the oxidizable substrate, pent-4-enoate decreases the carbamoyl phosphate concentration in mitochondria incubated without ornithine to minimize citrulline synthesis and impairs the mitochondrial uptake of ornithine, but it has neither effect when succinate is the oxidizable substrate. 4. Propionate, butyrate and crotonate also inhibit mitochondrial citrulline synthesis, but much less than pent-4-enoate. 5. Acetate, pentanoate, pent-2-enoate, hexanoate, octanoate, isovalerate, tiglylate and α-methylbutyrate have little or no effect on mitochondrial citrulline synthesis.

scholarly journals Adaptive changes in the capacity of systems used for the synthesis of citrulline in rat liver mitochondria in response to high- and low-protein diets

1974 ◽  
Vol 142 (2) ◽  
pp. 359-364 ◽  
Author(s):  
J. D. McGivan ◽  
Norah M. Bradford ◽  
J. B. Chappell
Keyword(s):  
Nitrogen Source ◽  
High Protein Diet ◽  
Liver Mitochondria ◽  
High Protein ◽  
Protein Diet ◽  
Rat Liver Mitochondria ◽  
Standard Diet ◽  
Adaptive Changes ◽  
Low Protein ◽  
Citrulline Synthesis

1. Citrulline synthesis was measured in mitochondria from rats fed on a standard diet, a high-protein diet, or on glucose. 2. With NH4Cl as the nitrogen source the rate of citrulline synthesis was higher in mitochondria from rats fed on a high-protein diet than in those from rats fed on a standard diet. When rats were fed solely on glucose the rate of synthesis of citrulline from NH4Cl was very low. 3. With glutamate as the nitrogen source the relative rates of citrulline synthesis were much lower than when NH4Cl was present, but similar adaptive changes occurred. 4. The activity of the mitochondrial glutamate-transporting system increased two to three times on feeding rats on a high-protein diet, but the Km for glutamate was unchanged. 5. Adaptive changes in certain intramitochondrial enzymes were also measured. 6. The results were interpreted to indicate that when an excess of substrate was present, citrulline synthesis from NH4Cl was rate-limited by the intramitochondrial concentration of N-acetyl-glutamate, but citrulline synthesis from glutamate was rate-limited primarily by the activity of the glutamate-transporting system.

scholarly journals Relationship between the Rate of Citrulline Synthesis and Bulk Changes in the Intramitochondrial ATP/ADP Ratio in Rat-Liver Mitochondria

1981 ◽  
Vol 113 (2) ◽  
pp. 295-302 ◽  
Author(s):  
Ron J. A. WANDERS ◽  
George M. WOERKOM ◽  
Ron F. NOOTEBOOM ◽  
Alfred J. MEIJER ◽  
Joseph M. TAGER
Keyword(s):  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Citrulline Synthesis

scholarly journals Energetics of citrulline synthesis by rat liver mitochondria.

1981 ◽  
Vol 256 (14) ◽  
pp. 7287-7297
Author(s):  
J.R. Williamson ◽  
R. Steinman ◽  
K. Coll ◽  
T.L. Rich
Keyword(s):  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Citrulline Synthesis

Effect of propionate and pyruvate on citrulline synthesis and ATP content in rat liver mitochondria

1979 ◽  
Vol 90 (1) ◽  
pp. 327-332 ◽  
Author(s):  
Liliane Cathelineau ◽  
Françoise P. Petit ◽  
François X Coudé ◽  
Pierre P. Kamoun
Keyword(s):  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Atp Content ◽  
Citrulline Synthesis

scholarly journals Inhibition of carbamoyl-phosphate synthase (ammonia) by Tris and Hepes. Effect on Ka for N-acetylglutamate

1987 ◽  
Vol 243 (1) ◽  
pp. 273-276 ◽  
Author(s):  
P Lund ◽  
D Wiggins
Keyword(s):  
Rat Liver ◽  
Phosphate Buffer ◽  
Active Enzyme ◽  
Urea Synthesis ◽  
Carbamoyl Phosphate ◽  
A Value ◽  
Phosphate Synthase

The apparent Ka for N-acetylglutamate of rat liver carbamoyl-phosphate synthase is 11 microM in phosphate buffer, a value 10-fold lower than reported in other buffer systems. Tris and Hepes inhibit competitively with N-acetylglutamate. The proportion of carbamoyl-phosphate synthase in the active enzyme-acetylglutamate complex in vivo may be higher than previous calculations suggest, which re-opens the question of the involvement of N-acetylglutamate in the regulation of urea synthesis.

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