Yanykin D V, Khorobrykh A A, Terentyev V V, Klimov V V
Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region, Russia, 142290.
Photosynth Res. 2017 Sep;133(1-3):129-138. doi: 10.1007/s11120-017-0373-z. Epub 2017 Mar 27.
Earlier the catalase-insensitive formation of organic hydroperoxides (via the interaction of organic radicals produced due to redox activity of P (or TyrZ) with molecular oxygen) has been found in Mn-depleted PS2 preparations (apo-WOC-PS2) by Khorobrykh et al. (Biochemistry 50:10658-10665, 2011). The present work describes a second pathway of the photoproduction of organic peroxides on the donor side of PS2. It was shown that illumination of CaCl-treated PS2 membranes (deprived of the PS2 extrinsic proteins without removal of the Mn-containing water-oxidizing complex) (CaCl-PS2) led to the photoproduction of highly lipophilic organic hydroperoxides (LP-OOH) (in amount corresponding to 1.5 LP-OOH per one reaction center of PS2) which significantly increased upon the addition of exogenous electron acceptor potassium ferricyanide (to 4.2 LP-OOH per one reaction center). Addition of catalase (200 U/ml) before illumination inhibited ferricyanide-induced photoproduction of hydroperoxides while no effect was obtained by adding catalase after illumination or by adding inactivated catalase before illumination. The hydroperoxide photoproduction was inhibited by the addition of exogenous electron donor for PS2, diphenylcarbazide or diuron (inhibitor of the electron transfer in PS2). The addition of exogenous hydrogen peroxide to the CaCl-PS2 led to the production of highly lipophilic organic hydroperoxides in the dark (3.2 LP-OOH per one reaction center). We suggest that the photoproduction of highly lipophilic organic hydroperoxides in CaCl-PS2 preparations occurs via redox activity of HO produced on the donor side of PS2.
此前，霍罗布里赫等人（《生物化学》50:10658 - 10665，2011年）在锰耗尽的光系统II制剂（脱辅基水氧化复合物 - 光系统II）中发现了有机氢过氧化物的过氧化氢酶不敏感形成（通过磷（或酪氨酸Z）的氧化还原活性产生的有机自由基与分子氧的相互作用）。本研究描述了光系统II供体侧有机过氧化物光生成的第二条途径。结果表明，用氯化钙处理的光系统II膜（去除了光系统II的外在蛋白但未去除含锰的水氧化复合物）（氯化钙 - 光系统II）受光照会导致生成高度亲脂性的有机氢过氧化物（LP - OOH）（其量相当于每个光系统II反应中心有1.5个LP - OOH），添加外源电子受体铁氰化钾后该量显著增加（达到每个反应中心4.2个LP - OOH）。光照前添加过氧化氢酶（200 U/ml）可抑制铁氰化物诱导的氢过氧化物光生成，而光照后添加过氧化氢酶或光照前添加失活的过氧化氢酶则无此效果。添加光系统II的外源电子供体二苯基卡巴肼或敌草隆（光系统II中电子转移的抑制剂）可抑制氢过氧化物的光生成。向氯化钙 - 光系统II中添加外源过氧化氢会在黑暗中导致生成高度亲脂性的有机氢过氧化物（每个反应中心3.2个LP - OOH）。我们认为，氯化钙 - 光系统II制剂中高度亲脂性有机氢过氧化物的光生成是通过光系统II供体侧产生的羟基自由基的氧化还原活性实现的。
