Levine R, Hirayama B, Wright E M
Biochim Biophys Acta. 1984 Jan 25;769(2):508-10. doi: 10.1016/0005-2736(84)90338-9.
The effect of anions on Na+-cotransport of succinate, lactate, glucose, and phenylalanine was studied under voltage clamped conditions in brush-border membrane vesicles prepared from rabbit renal cortex. The initial rate of succinate uptake varied by an order of magnitude depending on the anion: the highest rates were obtained with fluoride and gluconate, and the lowest with iodide. The anion sequence corresponded with the inverse of the anion hydration energies. The kinetics of succinate uptake were measured in the presence of fluoride and chloride. There was no difference in the maximal rates of uptake, but the Kt in fluoride (0.30 mM) was less than half that in chloride (0.70 mM), i.e. Cl- behaved as a competitive inhibitor of succinate transport with a Ki of 150 mM. The uptake of L-lactate, D-glucose and L-phenylalanine was less sensitive to anions, and there was no correlation with hydration energies. We conclude that the anion effects on sugar and amino acid uptakes measured under open-circuit conditions are largely due to variations in membrane potential, but in the case of the dicarboxylate transporter anions behave as weak competitive inhibitors. The specificity of the anion inhibition suggests that the dicarboxylate binding sites have a weak field strength relative to water.
在电压钳制条件下，对从兔肾皮质制备的刷状缘膜囊泡中，阴离子对琥珀酸、乳酸、葡萄糖和苯丙氨酸的钠协同转运的影响进行了研究。琥珀酸摄取的初始速率根据阴离子的不同而变化一个数量级：氟化物和葡萄糖酸盐的摄取速率最高，碘化物的最低。阴离子序列与阴离子水合能的倒数相对应。在氟化物和氯化物存在的情况下，测定了琥珀酸摄取的动力学。摄取的最大速率没有差异，但氟化物中的Kt（0.30 mM）小于氯化物中的一半（0.70 mM），即Cl-表现为琥珀酸转运的竞争性抑制剂，Ki为150 mM。L-乳酸、D-葡萄糖和L-苯丙氨酸的摄取对阴离子不太敏感，且与水合能无关。我们得出结论，在开路条件下测得的阴离子对糖和氨基酸摄取的影响主要是由于膜电位的变化，但就二羧酸转运体而言，阴离子表现为弱竞争性抑制剂。阴离子抑制的特异性表明，二羧酸结合位点相对于水具有较弱的场强。
