Gustafson L A, Romp N, van Woerkom G M, Meijer A J
E. C. Slater Institute, University of Amsterdam, The Netherlands.
Eur J Biochem. 1994 Jul 15;223(2):553-6. doi: 10.1111/j.1432-1033.1994.tb19024.x.
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.
已知氨基酸可通过增加细胞体积来刺激糖原合成[巴凯，A.，于埃，L.，梅杰，A. J.，范沃科姆，G. M. & 普洛姆普，P. J. A. M.（1990）《生物化学杂志》265，955 - 959]。然而，最近有人提出，尿素生成的中间产物氨基甲酰磷酸可通过葡萄糖 - 6 - 磷酸酶系统的氨基甲酰磷酸：葡萄糖磷酸转移酶活性作为葡萄糖磷酸化的底物。这一假设可以解释谷氨酰胺和脯氨酸等氨基酸对糖原生成的刺激作用[博德，A. M. & 诺德利，R. C.（1993）《生物化学杂志》268，16298 - 16301]。为了进一步研究氨基甲酰磷酸在糖原生成中可能发挥的作用，将分离的肝细胞在各种条件下孵育，以控制尿素生成、糖原生成和氨基甲酰磷酸水平。我们的数据表明，氨基甲酰磷酸水平与氨基酸刺激的糖原生成无关，并且尿素生成和糖原生成不是相互竞争的代谢途径。
