Carbamoyl phosphate and ureagenesis are not involved in amino-acid-stimulated glycogenesis.
Amino acids are known to stimulate glycogen synthesis via an increase in cell volume [Baquet, A., Hue, L., Meijer, A. J., van Woerkom, G. M. & Plomp, P. J. A. M. (1990) J. Biol. Chem. 265, 955-959]. It has recently been postulated, however, that carbamoyl phosphate, an intermediate of ureagenesis, can function as a substrate for glucose phosphorylation via carbamoyl-phosphate:glucose phosphotransferase activity of the glucose-6-phosphatase system. This hypothesis would account for the stimulation of glycogenesis by amino acids such as glutamine and proline [Bode, A. M. & Nordlie, R. C. (1993) J. Biol. Chem. 268, 16298-16301]. To further examine the role carbamoyl phosphate may play in glycogenesis, isolated hepatocytes were incubated under a variety of conditions to manipulate ureagenesis, glycogenesis and carbamoyl-phosphate levels. Our data indicate that carbamoyl-phosphate levels do not correlate with amino-acid-stimulated glycogenesis and that ureagenesis and glycogenesis are not competing metabolic pathways.
Gustafson
L A
LA
E. C. Slater Institute, University of Amsterdam, The Netherlands.
Romp
N
N
van Woerkom
G M
GM
Meijer
A J
AJ
D000596:Amino Acids / Q000494:pharmacology; D000641:Ammonia / Q000378:metabolism*; D000818:Animals; D002221:Carbamyl Phosphate / Q000378:metabolism*; D002478:Cells, Cultured; D005947:Glucose / Q000378:metabolism; D006003:Glycogen / Q000096:biosynthesis*; D007038:Hypotonic Solutions / Q000494:pharmacology; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008297:Male; D009952:Ornithine / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D010848:Picolinic Acids / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D014508:Urea / Q000378:metabolism*
D000596:Amino Acids; D007038:Hypotonic Solutions; D010848:Picolinic Acids; D002221:Carbamyl Phosphate; D000641:Ammonia; C008363:3-mercaptopicolinic acid; D014508:Urea; D006003:Glycogen; D009952:Ornithine; D005947:Glucose