Wolff C, Büchel K H, Renger G
Z Naturforsch C Biosci. 1975 Mar-Apr;30(2):172-82. doi: 10.1515/znc-1975-3-407.
The effect of alpha-bromo-alpha-benzylmalodinitril (BBMD) on the oxygen evolution and on the absorption changes at 515 nm and 704 nm has been investigated in spinach chloroplasts. It has been found: 1. Under repetitive flash excitation conditions, where the back reaction around system II is practically excluded for kinetical reasons, BBMD does not resotre the 515 nm absorption change in DCMU poisoned chloroplasts. 2. Under single flash excitation conditions, where the back reaction around system II becomes prominent in the presence of DCMU, BBMD moderately inhibits this back reaction. The deleterious effect is pronounced by preillumination with short flashes during the BBMD incubation period of the chloroplasts in the absence of DCMU. 3. Incubation of the chloroplasts with BBMD leads to an activity loss of oxygen evolution which increases with the time td between the repetitive short excitation flashes and with the dark incubation time. Preillumination during the incubation period with tbbmd significantly enhances the effect. 4. In the absence of artificial electron acceptors BBMD suppresses in DCMU poisoned chloroplasts the 704 nm absorption change reflecting an internal cyclic electron flow around system I. On the other hand the linear electron transport at system I mediated by DCIP plus ascorbate as electron donor couple and benzylviologen as electron acceptor is not distrubed by BBMD. 5. BBMD incubation of chloroplasts accelerates the decay rate of the field indicating 515 nm absorption change. Based on these experimental findings the conclusion has been drawn, that -- in contrast to the assumption of Brandon and Elgersma (Biochim. Biophys. Acta 292, 753--762 [1973]) -- BBMD does not accept electrons from the primary electron acceptor X 320 of system II in DCMU poisoned chloroplasts. BBMD rather acts as a system I electron acceptor. Furthermore, BBMD exerts deleterious effects on the center of photosystem II, accompanied by a weak ADRY-effect on the water-splitting enzyme system Y. As a tentative explanation of the BBMD-action on system II it is assumed that BBMD transforms the photochemical centers of system II into dissipative energy sinks.
研究了α-溴-α-苄基丙二腈（BBMD）对菠菜叶绿体中氧气释放以及515nm和704nm处吸收变化的影响。结果发现：1. 在重复闪光激发条件下，由于动力学原因系统II周围的反向反应实际上被排除，BBMD不能恢复被二氯苯基二甲基脲（DCMU）毒害的叶绿体中515nm处的吸收变化。2. 在单次闪光激发条件下，在存在DCMU时系统II周围的反向反应变得显著，BBMD适度抑制这种反向反应。在没有DCMU的情况下，在叶绿体的BBMD孵育期间用短闪光预照明显加剧了这种有害作用。3. 叶绿体与BBMD孵育导致氧气释放活性丧失，其随着重复短激发闪光之间的时间td以及暗孵育时间增加。在孵育期间用tbbmd预照显著增强了这种效应。4. 在没有人工电子受体的情况下，BBMD在被DCMU毒害的叶绿体中抑制反映围绕系统I的内部循环电子流的704nm吸收变化。另一方面，由二氯靛酚（DCIP）加抗坏血酸作为电子供体对和苄基紫精作为电子受体介导的系统I处的线性电子传递不受BBMD干扰。5. 叶绿体的BBMD孵育加速了指示515nm吸收变化的电场衰减速率。基于这些实验结果得出结论，即——与布兰登和埃尔格斯马的假设（生物化学与生物物理学报292, 753 - 762 [1973]）相反——在被DCMU毒害的叶绿体中，BBMD不从系统II的初级电子受体X 320接受电子。BBMD反而充当系统I的电子受体。此外，BBMD对光系统II的中心产生有害影响，同时对水裂解酶系统Y有微弱的ADRY效应。作为对BBMD对系统II作用的初步解释，假定BBMD将系统II的光化学中心转化为耗散能量的汇。
