Ohyashiki T, Takeuchi M, Mohri T
J Biochem. 1984 Mar;95(3):881-6. doi: 10.1093/oxfordjournals.jbchem.a134681.
Cation specificity and effects of pH and temperature on membrane aggregation of porcine intestinal brush borders were studied in terms of the turbidity change of the membrane suspensions due to the addition of polyvalent cations. Monovalent cations (K+ and Na+) did not induce the membrane aggregation at 5 mM or below. Divalent and trivalent cations induced membrane aggregation even below 0.5 mM in the following orders of effectiveness: Hg2+ much greater than Cd2+ greater than Zn2+ greater than Mn2+ greater than Ca2+ greater than or equal to Ba2+ greater than Sr2+ greater than or equal to Mg2+ and Lu3+ greater than Yb3+ greater than Nd3+ = Er3+ = Tb3+ greater than Ce3+ greater than La3+, respectively. The aggregation of membranes induced by these polyvalent cations was reversible. Membrane aggregation induced by either divalent or trivalent cations followed saturation kinetics with increasing cation concentration and the apparent dissociation constants of these cations for the membranes were estimated to be at 4-6 mM for divalent cations (Ca2+, Mn2+, and Sr2+) and 1-2 mM for trivalent cations (Lu3+, Tb3+, and La3+). Cd2+ and Hg2+ had peculiarly much lower dissociation constants than any other divalent cations tested, being rather comparable to trivalent ones. The membrane aggregation induced by Ca2+, Mn2+, or Sr2+ was independent of pH in the range of 6.6 to 8.0, whereas that induced by Tb3+ or Cd2+ was linearly enhanced with increasing pH, very steeply above pH 7.0. The membrane aggregation induced by Cd2+, Hg2+, or Tb3+ was enhanced steadily with increasing temperature between 15 and 45 degrees C. On the other hand, Ca2+-induced aggregation showed a peak at around 30 degrees C in the temperature dependence profile, still being enhanced above 40 degrees C.
通过添加多价阳离子后膜悬浮液的浊度变化，研究了阳离子特异性以及pH值和温度对猪小肠刷状缘膜聚集的影响。单价阳离子（K⁺和Na⁺）在5 mM或更低浓度时不会诱导膜聚集。二价和三价阳离子即使在低于0.5 mM时也会诱导膜聚集，其有效性顺序如下：Hg²⁺远大于Cd²⁺大于Zn²⁺大于Mn²⁺大于Ca²⁺大于或等于Ba²⁺大于Sr²⁺大于或等于Mg²⁺，以及Lu³⁺大于Yb³⁺大于Nd³⁺ = Er³⁺ = Tb³⁺大于Ce³⁺大于La³⁺。这些多价阳离子诱导的膜聚集是可逆的。二价或三价阳离子诱导的膜聚集随阳离子浓度增加遵循饱和动力学，这些阳离子对膜的表观解离常数估计对于二价阳离子（Ca²⁺、Mn²⁺和Sr²⁺）为4 - 6 mM，对于三价阳离子（Lu³⁺、Tb³⁺和La³⁺）为1 - 2 mM。Cd²⁺和Hg²⁺的解离常数比所测试的任何其他二价阳离子都特别低，与三价阳离子相当。Ca²⁺、Mn²⁺或Sr²⁺诱导的膜聚集在6.6至8.0的pH范围内与pH无关，而Tb³⁺或Cd²⁺诱导的膜聚集随pH升高呈线性增强，在pH 7.0以上非常陡峭。Cd²⁺、Hg²⁺或Tb³⁺诱导的膜聚集在15至45摄氏度之间随温度升高而稳步增强。另一方面，Ca²⁺诱导的聚集在温度依赖性曲线中在约30摄氏度处出现峰值，在40摄氏度以上仍在增强。
