碳酸氢盐在哺乳动物谷氨酰胺代谢调节中的作用。

A role for bicarbonate in the regulation of mammalian glutamine metabolism.

Baverel G, Lund P

Biochem J. 1979 Dec 15;184(3):599-606. doi: 10.1042/bj1840599.

Abstract

The concentration of HCO3- (independent of any change of pH) exerts different effects on glutamine metabolism in rat kidney-cortex tubules, hepatocytes and enterocytes.2. In kidney tubules HCO3- (10.5-50 MM) has no effect on glutaminase (EC 3.5.1.2), whereas glutamate dehydrogenase (EC 1.4.1.3) is inhibited as HCO3- concentration is increased. The result is that flux through the entire glutamate-to-glucose pathway is inhibited by increasing HCO3- concentrations. A large proportion (more than 30%) of the glutamine removed undergoes complete oxidation. 3. In hepatocytes, and to a smaller extent in enterocytes, HCO3- is an accelerator of glutaminase. Synthesis of glucose and urea from glutamine in hepatocytes increases as HCO3- concentration is increased. Calculations show that fumarate, formed via aspartate aminotransferase and arginino-succinate lyase, is the precursor of the glucose. There is no complete oxidation of the carbon skeleton of glutamine in hepatocytes. 4. Leucine at near-physiological concentrations (0.1-1 mM) is an accelerator of glutaminase in hepatocytes, but not in kidney tubules or in enterocytes. 5. The results are discussed in relation to regulation of acid/base balance in vivo.

摘要

碳酸氢根离子的浓度（与pH值的任何变化无关）对大鼠肾皮质肾小管、肝细胞和肠细胞中的谷氨酰胺代谢产生不同影响。2. 在肾小管中，碳酸氢根离子（10.5 - 50毫摩尔）对谷氨酰胺酶（EC 3.5.1.2）没有影响，而随着碳酸氢根离子浓度增加，谷氨酸脱氢酶（EC 1.4.1.3）受到抑制。结果是，随着碳酸氢根离子浓度增加，整个谷氨酸到葡萄糖途径的通量受到抑制。被去除的谷氨酰胺中有很大一部分（超过30%）发生完全氧化。3. 在肝细胞中，以及在较小程度上在肠细胞中，碳酸氢根离子是谷氨酰胺酶的促进剂。随着碳酸氢根离子浓度增加，肝细胞中由谷氨酰胺合成葡萄糖和尿素的过程增加。计算表明，通过天冬氨酸转氨酶和精氨琥珀酸裂解酶形成的延胡索酸是葡萄糖的前体。在肝细胞中谷氨酰胺的碳骨架没有完全氧化。4. 接近生理浓度（0.1 - 1毫摩尔）的亮氨酸是肝细胞中谷氨酰胺酶的促进剂，但在肾小管或肠细胞中不是。5. 结合体内酸碱平衡的调节对结果进行了讨论。