无机磷影响叠氮钠对ATP合成酶合成活性的抑制

利用ADP和放射性磷直接合成ATP的方法，研究了无机磷(P_i)和叠氮钠对猪心线粒体ATP合成酶（F₁F_O-ATPase）ATP合成活性的影响.结果发现无机磷除作为合成ATP的底物参与F₁F_O-ATPase的合成反应外，还对F₁F_O-ATPase的合成活性呈现抑制作用，在1 mmol/L ADP存在时，随着P_i浓度由0.01～10 mmol/L增加,抑制合成作用越来越强.与叠氮钠在低浓度时(小于1 mmol/L)只抑制ATP水解,不影响ATP合成的观点不同.实验结果显示0.1 mmol/L叠氮钠表观激活F₁F_O-ATPase的ATP合成活性，且激活程度与反应体系中所加P_i的浓度呈负相关.当固定P_i浓度（0.1 mmol/L）后，随着叠氮钠浓度的增加表观激活程度也在变化，叠氮钠与磷浓度相等时表观激活程度最大，直至叠氮钠浓度接近0.5 mmol/L时，开始呈现表观抑制现象，叠氮钠浓度高于1 mmol/L之后，就出现解偶联现象.

The Effects of Pi on the Inhibition of ATP Synthesis Activity of F1FO-ATPase by Azide

Using ATP directly synthetical method with ADP and radiophosphate, the effects of azide and inorganic phosphate on the ATP synthesis of F 1F O ATPase from pig heart mitochondria are investigated. It is found that P i not only takes an active part in ATP synthesis as a substrate, but also has an inhibition effect on ATP synthesis of F 1F O ATPase. In the presence of 1 mmol/L ADP the inhibition increases with the increase of P i concentration from 0 01 mmol/L to 10 mmol/L. The viewpoint is different from that azide only inhibites ATP hydrolysis but not affects the ATP synthesis at low concentration (<1 mmol/L). The results indicate that 0 1 mmol/L azide apparently activates ATP synthesis of F 1F O ATPase. The activation is negatively related to the concentration of P i in the reaction system. When the concentration of P i is kept at 0 1 mmol/L , with the increase of azide concentration, the apparent activation degree of ATP synthesis by azide is changed. When the concentrations of azide and P i are equal, the apparent activation by azide is the biggest. The apparent inhibition of ATP synthesis by azide would not begin until the concentration of azide reaches near 0 5 mmol/L. After the concentration of azide is higher than 1 mmol/L, the uncoupling of F 1F O ATPase appears. The mechanism of the roles of azide and P i is discussed.