Effect of Temperature and External pH on the Cytoplasmic pH of Chara corallina
Effect of Temperature and External pH on the Cytoplasmic pH of Chara corallina
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温度和外部pH值对珊瑚轮胞质pH值的影响
DOI：
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发表时间：
1978
期刊：
影响因子：
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通讯作者：
F. A. Smith
中科院分区：
文献类型：
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作者：
J. Raven;F. A. Smith
测量珊瑚轮藻的细胞质 pH (pHc)（根据 f14C]DMO 分布）作为外部 pH (pH0) 和温度的函数。 pHc接近7，25℃时pHc为7-80； pHc 增加 0-005 个 pH 单位 °C_1 温度降低，即 5 °C 时 pHc 为 7-90。当 pH0 接近 5-5 时，pHc 随着温度降低而增加，在 25 到 15 °C 之间为 0-015 个单位 °C-1，但在 15 到 5 °C 之间为 0-005 个单位 °C_1。这意味着与 25 °C 相比，在 5 或 15 °C 时可以更精确地调节 pHc 和 pH0 的变化。观察到的 dpHJdT 通常小于维持恒定 H+/OH" 所需的 -0-017 单位 °C-1，或蛋白质中组氨酸随温度变化的恒定分数电离所需的值。它更接近于维持磷酸化化合物或 COj-HCOj 的分数电离所需的值。dpHjdT 的值对细胞代谢的几个调节方面具有重要影响。这些包括（全部作为温度的函数）酶反应速率、 A//H+（在质膜处（以及因此可用于共转运过程的能量），以及通过控制质膜处双向 H+ 通量来调节 pHc 的机制。
Cytoplasmic pH (pHc) in Chara corallina was measured (from f14C]DMO distribution) as a function of external pH (pH0) and temperature. With pHc near 7, pHc at 25 °C is 7-80; pHc increases by 0-005 pH units °C_1 temperature decrease, i.e. pHc at 5 °C is 7-90. With pH0 near 5-5, the increase in pHc with decreasing temperature is 0-015 units °C-1 between 25 and 15 °C, but 0-005 units °C_1 between 15 and 5 °C. This implies a more precise regulation of pHc with variations in pH0 at 5 or 15 °C compared with 25 °C. The observed dpHJdT is generally smaller than the -0-017 units °C-1 needed to maintain a constant H+/OH", or a constant fractional ionization of histidine in protein, with variation in temperature. It is closer to that needed to maintain the fractional ionization of phosphorylated compounds or of COj-HCOj. The value of dpHjdT has important implications for several regulatory aspects of cell metabolism. These include (all as a function of temperature) the rates of enzyme reactions, the A//H+ (at the plasmalemma (and hence the energy available for cotransport processes), and the mechanism for pHc regulation by the control of bidirectional H+ fluxes at the plasmalemma.