Dorando F C, Crane R K
Biochim Biophys Acta. 1984 May 30;772(3):273-87. doi: 10.1016/0005-2736(84)90144-5.
The Na+-dependent D-glucose transport reaction in rabbit jejunal brush-border vesicles was studied. Initial rate data were obtained by fitting a polynomial equation to progress curves at different D-glucose concentrations and extracting the slope of the tangent at zero-time. Kinetic replots of the initial rate values produced biphasic Hofstee patterns indicative of two pathways for transport distinguished by their Km values for glucose. Neither was dependent on the presence of a membrane potential. Both were dependent on Na+ and both were inhibited by phlorizin. Increasing external sodium was found to elevate the apparent Vmax for both pathways. Internal sodium was inhibitory. Pulsed progress curve analysis indicated that the effect of internal sodium was best characterized as carrier sequestration by a sodium-carrier binary complex. Inhibition by internal sodium was completely reversed by the presence, internally, of D-glucose. The presence of two pathways and the kinetic constants for these pathways do not agree with the conclusions of Hopfer and Groseclose (1980) J. Biol. Chem. 255, 4453-4462). Experiments are presented which bear on the reason for the disagreement.
对兔空肠刷状缘小泡中依赖 Na⁺的 D-葡萄糖转运反应进行了研究。通过将多项式方程拟合到不同 D-葡萄糖浓度下的进程曲线，并提取零时间处切线的斜率来获得初始速率数据。初始速率值的动力学重绘产生双相霍夫施泰模式，表明存在两种转运途径，以它们对葡萄糖的 Km 值区分。两者均不依赖于膜电位。两者均依赖于 Na⁺，且均受根皮苷抑制。发现增加细胞外钠会提高两种途径的表观 Vmax。细胞内钠具有抑制作用。脉冲进程曲线分析表明，细胞内钠的作用最适合描述为钠-载体二元复合物对载体的隔离。细胞内存在 D-葡萄糖可完全逆转细胞内钠的抑制作用。两种途径的存在以及这些途径的动力学常数与霍普费尔和格罗斯克洛斯（1980 年，《生物化学杂志》255 卷，4453 - 4462 页）的结论不一致。本文给出了一些实验，这些实验与产生分歧的原因有关。
