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首页> 外文期刊>FEBS Open Bio >Kinetic studies on the oxidation of semiquinone and hydroquinone forms of Arabidopsis cryptochrome by molecular oxygen
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Kinetic studies on the oxidation of semiquinone and hydroquinone forms of Arabidopsis cryptochrome by molecular oxygen

机译：分子氧氧化拟南芥隐色素半醌和对苯二酚形式的动力学研究

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Cryptochromes (crys) are flavoprotein photoreceptors present throughout the biological kingdom that play important roles in plant development and entrainment of the circadian clock in several organisms. Crys non-covalently bind flavin adenine dinucleotide (FAD) which undergoes photoreduction from the oxidised state to a radical form suggested to be active in signalling in vivo. Although the photoreduction reactions have been well characterised by a number of approaches, little is known of the oxidation reactions of crys and their mechanisms. In this work, a stopped-flow kinetics approach is used to investigate the mechanism of cry oxidation in the presence and absence of an external electron donor. This in vitro study extends earlier investigations of the oxidation of Arabidopsis cryptochrome1 by molecular oxygen and demonstrates that, under some conditions, a more complex model for oxidation of the flavin than was previously proposed is required to accommodate the spectral evidence (see P. Muller and M. Ahmad (2011) J. Biol. Chem. 286, 21033-21040 [1]). In the absence of an electron donor, photoreduction leads predominantly to the formation of the radical FADH^?. Dark recovery most likely forms flavin hydroperoxide (FADHOOH) requiring superoxide. In the presence of reductant (DTT), illumination yields the fully reduced flavin species (FADH^-). Reaction of this with dioxygen leads to transient radical (FADH^?) and simultaneous accumulation of oxidised species (FAD), possibly governed by interplay between different cryptochrome molecules or cooperativity effects within the cry homodimer.
机译：隐色染料（哭声）是整个生物界中存在的黄素蛋白感光体，它们在几种生物中的植物发育和昼夜节律的携带中起重要作用。 Crys非共价结合黄素腺嘌呤二核苷酸（FAD），该黄素腺嘌呤二核苷酸（FAD）经历了从氧化态到自由基形式的光还原，在体内信号传导中具有活性。尽管光还原反应已通过多种方法很好地表征，但对哭声的氧化反应及其机理知之甚少。在这项工作中，采用停流动力学方法研究在存在和不存在外部电子供体的情况下低温氧化的机理。这项体外研究扩展了对分子氧氧化拟南芥隐色素1的早期研究，并表明在某些条件下，需要比以前建议的更复杂的黄酮氧化模型来适应光谱证据（参见P.Muller和M.Ahmad（2011）J.Biol.Chem.286，21033-21040 [1]）。在没有电子给体的情况下，光还原主要导致自由基FADH 2+的形成。黑暗恢复很可能形成需要超氧化物的黄素氢过氧化物（FADHOOH）。在存在还原剂（DTT）的情况下，光照会产生完全还原的黄素类物质（FADH ^-）。其与双氧的反应导致瞬态自由基（FADH +）和氧化物质（FAD）的同时积累，这可能由不同的隐色染料分子之间的相互作用或cry均二聚体内的协同作用所决定。

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