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Citrulline synthesis in rat tissues ..

AB - High levels of both glutamine synthetase and a unique L-glutamine- and N-acetyl-L-glutamate-dependent carbamoyl phosphate synthetase are present in the mitochondria in livers of marine urea-retaining elasmobranchs (Casey, C. A., and Anderson, P. M. (1982) J. Biol. Chem. 257, 8449-8453). On the basis of these observations it has been suggested that in these species carbamoyl phosphate and, consequently, one of the nitrogen atoms of citrulline and, ultimately, urea, are derived directly from glutamine rather than from ammonia as occurs in mammalian ureotelic species. The purpose of this study was to obtain evidence for this role of glutamine. Isolated hepatic mitochondria from Squalus acanthias incubated with ammonia plus glutamate, ornithine, bicarbonate, inorganic phosphate, and succinate as an energy source were found to synthesize citrulline at a rate comparable to the rate of urea synthesis observed in vivo. Citrulline synthesis proceeds at maximal rates even when the ammonia concentration is as low as 0.05 mM and is stoichiometric with the amount of ammonia initially present. Synthesis from ammonia does proceed in the absence of glutamate, but a much higher concentration of ammonia (congruent to 4 mM) is required to achieve a half-maximal rate. Glutamine can substitute for ammonia plus glutamate as the nitrogen-donating substrate for citrulline synthesis. Selective inhibition of the glutamine-dependent activity of the carbamoyl phosphate synthetase in the isolated mitochondria completely inhibits the ability of the mitochondria to synthesize citrulline from glutamine or from ammonia plus glutamate, whereas selective inhibition of glutamine synthetase inhibits citrulline synthesis from ammonia plus glutamate, but not from glutamine. These observations provide direct evidence that ammonia assimilation for citrulline synthesis (and, therefore, urea synthesis) in these species involves intermediate formation of glutamine.

Nitric oxide (NO) is endogenously synthesized from L-arginine and L-citrulline.

L-Citrulline is a naturally occurring non-essential amino acid. Although L-Citrulline is not used in protein synthesis, it has several important functions with respect to amino acid and protein metabolism.

Citrulline synthesis in rat-liver mitochondria - …

Under all conditions used, citrulline synthesis was strictly correlated with the bulk intramitochondrial ATP/ADP ratio.

The curve relating citrulline synthesis and intramitochondrial ATP/ADP was shifted towards lower ATP/ADP ratios when the activity of carbamoyl-phosphate synthetase was enhanced by increasing the mitochondrial content of N-acetylglutamate.

Citrulline synthesis was used as an intramitochondrial ATP-utilizing system, and glucose-6-phosphate synthesis as an extramitochondrial ATP-utilizing system.

Citrulline: Better Muscle Pumps and Improved Protein Synthesis

L-Citrulline is involved in the formation of urea in the liver; and the synthesis and elimination of urea is essential for removing toxic protein metabolites from the body. In addition, L-Citrulline facilitates protein synthesis for muscle tissue retention and helps to maintain healthy protein balance.

N2 - High levels of both glutamine synthetase and a unique L-glutamine- and N-acetyl-L-glutamate-dependent carbamoyl phosphate synthetase are present in the mitochondria in livers of marine urea-retaining elasmobranchs (Casey, C. A., and Anderson, P. M. (1982) J. Biol. Chem. 257, 8449-8453). On the basis of these observations it has been suggested that in these species carbamoyl phosphate and, consequently, one of the nitrogen atoms of citrulline and, ultimately, urea, are derived directly from glutamine rather than from ammonia as occurs in mammalian ureotelic species. The purpose of this study was to obtain evidence for this role of glutamine. Isolated hepatic mitochondria from Squalus acanthias incubated with ammonia plus glutamate, ornithine, bicarbonate, inorganic phosphate, and succinate as an energy source were found to synthesize citrulline at a rate comparable to the rate of urea synthesis observed in vivo. Citrulline synthesis proceeds at maximal rates even when the ammonia concentration is as low as 0.05 mM and is stoichiometric with the amount of ammonia initially present. Synthesis from ammonia does proceed in the absence of glutamate, but a much higher concentration of ammonia (congruent to 4 mM) is required to achieve a half-maximal rate. Glutamine can substitute for ammonia plus glutamate as the nitrogen-donating substrate for citrulline synthesis. Selective inhibition of the glutamine-dependent activity of the carbamoyl phosphate synthetase in the isolated mitochondria completely inhibits the ability of the mitochondria to synthesize citrulline from glutamine or from ammonia plus glutamate, whereas selective inhibition of glutamine synthetase inhibits citrulline synthesis from ammonia plus glutamate, but not from glutamine. These observations provide direct evidence that ammonia assimilation for citrulline synthesis (and, therefore, urea synthesis) in these species involves intermediate formation of glutamine.

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Synthesis of citrulline from glutamine in pig enterocytes.

High levels of both glutamine synthetase and a unique L-glutamine- and N-acetyl-L-glutamate-dependent carbamoyl phosphate synthetase are present in the mitochondria in livers of marine urea-retaining elasmobranchs (Casey, C. A., and Anderson, P. M. (1982) J. Biol. Chem. 257, 8449-8453). On the basis of these observations it has been suggested that in these species carbamoyl phosphate and, consequently, one of the nitrogen atoms of citrulline and, ultimately, urea, are derived directly from glutamine rather than from ammonia as occurs in mammalian ureotelic species. The purpose of this study was to obtain evidence for this role of glutamine. Isolated hepatic mitochondria from Squalus acanthias incubated with ammonia plus glutamate, ornithine, bicarbonate, inorganic phosphate, and succinate as an energy source were found to synthesize citrulline at a rate comparable to the rate of urea synthesis observed in vivo. Citrulline synthesis proceeds at maximal rates even when the ammonia concentration is as low as 0.05 mM and is stoichiometric with the amount of ammonia initially present. Synthesis from ammonia does proceed in the absence of glutamate, but a much higher concentration of ammonia (congruent to 4 mM) is required to achieve a half-maximal rate. Glutamine can substitute for ammonia plus glutamate as the nitrogen-donating substrate for citrulline synthesis. Selective inhibition of the glutamine-dependent activity of the carbamoyl phosphate synthetase in the isolated mitochondria completely inhibits the ability of the mitochondria to synthesize citrulline from glutamine or from ammonia plus glutamate, whereas selective inhibition of glutamine synthetase inhibits citrulline synthesis from ammonia plus glutamate, but not from glutamine. These observations provide direct evidence that ammonia assimilation for citrulline synthesis (and, therefore, urea synthesis) in these species involves intermediate formation of glutamine.

Read L-Citrulline DL-Malate 2:1 Nutritional Information and Reviews.

We examined whether providing citrulline, a precursor for arginine and nitric oxide synthesis, would increase arterial blood flow, skeletal muscle microvascular perfusion, MPS, and signaling through mTORC1.

L-arginine and L-citrulline are amino acids

The present study determined the effectiveness of L-citrulline and/or GSH on markers indicative of NO synthesis in in vivo conditions with rodents and humans and also in an in vitro condition.

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