鼠肝线粒体呼吸链质子泵高能质子流向膜表面及其在能量偶联中的作用

HIGH ENERGY PROTONS ON MITOPLAST MEMBRANE INTERFACE UPON SUCCINATE OXIDATION AND ITS SIGNIFICANCE IN ENERGY COUPLING FUNCTION

利用面 △ψ感的荧光探针Ｒｈｏｄａｍｉｎｅ１２３，测定了琥珀酸脉冲引起的鼠肝线粒体内膜体 △ψ 时相的变化，同时用高精度ｐＨ电极测定了相应体系介质ｐＨ时相的变化。结果表明：线粒体跨膜电位的变化速率，快于介质ｐＨ的变化速率，并发现琥珀酸氧化时建立的 △ψ 所维持的时间，短于介质酸化所维持的时间，后者是个缓慢的回复过程，这两者之间存在有时间差。随着温度、Ｋ＋浓度和线粒体蛋白浓度的降低及琥珀酸浓度的增加，此两者的时间差亦相应增大。提示：线粒体内膜表面在能化时存在有被束缚的高能质子。利用铁氰化钾脉冲法证明线粒体内膜体呼吸链复合体（Ⅱ＋Ⅲ）的Ｈ＋／２ｅ比随着温度、Ｋ＋浓度及线粒体蛋白浓度的增高而降低，也支持上述观点。与此同时，线粒体内膜体的呼吸控制率随温度的下降而升高，说明膜表面质子对干线粒体的能量偶联具有更为重要的作用。

The△ψ of rat liver mitoplast was measured by using Rhodamine 123 fluorescence quenching method and the changes of the medium PH was measured with high sensitive PH electrode. There is a time difference between the △ψ of the mitoplast and the changes of medium PH induced by succinate pulse. This time difference increases with the increase of succinate concentration and decreases with the increase of the temperature. mitoplast protein concentration as well as the K+ concentration. This means that the protons ejected by redox enzyme of respiratory chain are retained at first on the interface of mitoplast membrane upon the energization. Besides, the H+/2e ratio of complex (Ⅱ +Ⅲ ) of rat liver mitoplast was obeserved to increase upon the increases of incubation temperature, mitoplast protein concentration or K+ concentration by using ferricynide pulse method. It also supports the idea mentioned above. Furthermore, the RCR was obeserved to increase upon the decrease of temperature. this set of experiment are considered to support the idea that the membrane surface protons may have some importance in the energy coupling process of mitoplast.