Stemler A, Jursinic P
Arch Biochem Biophys. 1983 Feb 15;221(1):227-37. doi: 10.1016/0003-9861(83)90139-x.
Inhibitors of carbonic anhydrase were tested for their effects on Photosystem II (PS II) activity in chloroplasts. We find that formate inhibition of PS II turnover rates increases as the pH of the reaction medium is lowered. Bicarbonate ions can inhibit PS II turnover rates. The relative potency of the anionic inhibitors N-3, I-, OA-c, and Cl- is the same for both carbonic anhydrase and PS II. The inhibitory effect of acetazolamide on PS II increases as light intensity decreases, indicating a lowering of quantum yields in the presence of the inhibitor. Imidazole inhibition of PS II increases with pH in a manner suggesting that the unprotonated form of the compound is inhibitory. Formate, bicarbonate, acetazolamide, and imidazole all inhibit DCMU-insensitive, silicomolybdate-supported oxygen evolution, indicating that the site(s) of action of the inhibitors is at, or before, the primary stable PS II electron acceptor, Q. This inhibitory effect of low levels of HCO-3 along with the known enhancement by HCO-3 of quinone-mediated electron flow suggests an antagonistic control effect on PS II photochemistry. We conclude that the responses of PS II to anions (formate, bicarbonate), acetazolamide, and imidazole are analogous to the responses shown by carbonic anhydrase. These findings suggest that the enzyme carbonic anhydrase may provide a model system to gain insight into the "bicarbonate-effect" associated with PS II in chloroplasts.
对碳酸酐酶抑制剂进行了测试，以研究其对叶绿体中光系统II（PS II）活性的影响。我们发现，随着反应介质pH值的降低，甲酸对PS II周转速率的抑制作用增强。碳酸氢根离子可抑制PS II周转速率。阴离子抑制剂N-3、I-、OA-c和Cl-对碳酸酐酶和PS II的相对效力相同。乙酰唑胺对PS II的抑制作用随光强降低而增强，表明在抑制剂存在下量子产率降低。咪唑对PS II的抑制作用随pH值升高而增强，这表明该化合物的未质子化形式具有抑制作用。甲酸、碳酸氢根、乙酰唑胺和咪唑均抑制DCMU不敏感、硅钼酸盐支持的放氧反应，这表明抑制剂的作用位点在初级稳定PS II电子受体Q处或之前。低水平HCO-3的这种抑制作用以及已知的HCO-3对醌介导的电子流的增强作用表明，其对PS II光化学具有拮抗控制作用。我们得出结论，PS II对阴离子（甲酸、碳酸氢根）、乙酰唑胺和咪唑的反应类似于碳酸酐酶的反应。这些发现表明，碳酸酐酶可能为深入了解叶绿体中与PS II相关的“碳酸氢根效应”提供一个模型系统。
