The reactivity of hydrazine with photosystem II strongly depends on the redox state of the water oxidizing system

FEBS Letters

Renger, G.¹  Messinger, J.¹ 

[1] Max Volmer Institut für Biophysikalische und Physikalische Chemie der Technischen Universität, Straße des 17. Juni 135, D 1000 Berlin, Germany

关键词: Photosystem II;    Water oxidation;    Si-state lifetimes;    Hydrazine;    Hydroxylamine;   

DOI  :  10.1016/0014-5793(90)80829-8

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The decay kinetics of the redox states S₂ and S₃ of the water-oxidizing enzyme have been analyzed in isolated spinach thylakoids in the absence and presence of the exogenous reductant hydrazine. In control samples without NH₂NH₂ a biphasic decay is observed. The rapid decline of S₂ and S₃ with y_D as reductant exhibits practically the same kinetics with t _1/2 = 6-7 s at pH = 7.2 and 7°C. The slow reduction (order of 5-10 min at 7°C) of S₂ and S₃ with endogenous electron donors other than y_D is about twice as fast for S₂ as for S₃ under these conditions. In contrast, the hydrazine-induced reductive shifts of the formal redox states S_i (i = 0⋯3) are characterized by a totally different kinetic pattern: (a) at 1 mMNH₂NH₂ and incubation on ice the decay of S₂ is estimated to be at least 25 times faster (t _1/2⩽0.4 min) than the corresponding reaction of S₃ (t _1/2≈13 min); (b) the NH₂NH₂-induced decay of S₂ is even slower (about twice) than the transformation of S₁ into the formal redox state ‘S₋₁’ (t _1/2≈6 min), which gives rise to the two-digit phase shift of the oxygen-yield pattern induced by a flash train in dark adapted thylakoids. (c) the NH₂NH₂-induced transformation S₀→‘S₋₂’ [Renger, Messinger and Hanssum (1990) in: Curr. Res. Photosynth. (Baltscheffsky, M., ed). Vol. 1, pp. 845-848, Kluwer, Dordrecht] is about three times faster (t _1/2≈ min) than the reaction. Based on these results, the following dependence on the redox state S_i of the reactivity towards NH₂NH₂ is obtained: S₃ < S₁ < S₀ ⪡ S₂. The implications of this surprising order of reactivity are discussed.

【 授权许可】

Unknown