Rate at which glutamine enters TCA cycle influences carbon atom fate in intestinal epithelial cells.
Rate at which glutamine enters TCA cycle influences carbon atom fate in intestinal epithelial cells.
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谷氨酰胺进入 TCA 循环的速率影响肠上皮细胞中碳原子的命运。
DOI：
10.1152/ajpgi.1998.275.6.g1299
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
Fleming,SE
中科院分区：
文献类型：
--
作者：
Quan,J;Fitch,MD;Fleming,SE
通过测量[1- 14 C]谷氨酰胺产生的CO2，评估了小肠上皮细胞中谷氨酰胺碳进入三羧酸（TCA）循环的情况，并将这些数据与[U-14 C]谷氨酰胺数据一起用于计算谷氨酰胺的部分氧化速率。从[1- 14 C]谷氨酰胺或[U-14 C]谷氨酰胺产生CO2显示饱和动力学，并且达到CO2产生的半最大速率所需的浓度分别为0.7和0.4 mmol/l。[1- 14 C]谷氨酰胺的最大速率是[U-14 C]谷氨酰胺的两倍。谷氨酰胺浓度的增加不会导致进入TCA循环的谷氨酰胺和谷氨酰胺氧化成比例增加。因此，谷氨酰胺的氧化分数随着谷氨酰胺浓度的增加而降低。分数氧化可以从谷氨酰胺碳进入TCA循环的速率来预测。氨基转移酶抑制剂（氨氧基）乙酸可减少谷氨酰胺进入TCA循环，并增加谷氨酰胺的氧化分数。谷氨酸碳进入TCA循环的速率约为谷氨酰胺衍生的谷氨酸碳的一半，并且当以与谷氨酰胺相等的浓度提供时具有更高的氧化分数。这些进入速率的差异可预测地解释了谷氨酰胺与谷氨酸碳的代谢命运的差异。
Glutamine carbon entry into the tricarboxylic acid (TCA) cycle was assessed in small intestinal epithelial cells by measuring CO2production from [1-14C]glutamine, and these data together with [U-14C]glutamine data were used to calculate fractional oxidation rates for glutamine. CO2production from either [1-14C]glutamine or [U-14C]glutamine showed saturation kinetics, and the concentration needed to achieve the half-maximal rate of CO2production was 0.7 and 0.4 mmol/l, respectively. Maximal rate for [1-14C]glutamine was twice that for [U-14C]glutamine. Increasing glutamine concentration did not cause proportional increases in glutamine entry into the TCA cycle and glutamine oxidation. Consequently, fractional oxidation of glutamine decreased with increasing glutamine concentration. Fractional oxidation could be predicted from the rate at which glutamine carbon entered the TCA cycle. (Aminooxy)acetic acid, an aminotransferase inhibitor, reduced entry of glutamine into the TCA cycle and increased fractional oxidation of glutamine. Glutamate carbon entered the TCA cycle at about one-half the rate of glutamine-derived glutamate carbon and had a higher fractional oxidation rate when provided at equivalent concentrations to glutamine. These differences in the rate of entry predictably account for the differences in the metabolic fate of glutamine vs. glutamate carbon.