Dark-operative protochlorophyllide reductase and nitrogenase: common mechanism for reduction of stable multiple-bonds

暗操作原叶绿素酯还原酶和固氮酶：稳定多重键还原的常见机制

• 批准号: 23370020
• 负责人: FUJITA Yuichi
• 金额: $ 11.73万
• 依托单位: Nagoya University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2011
• 资助国家: 日本
• 起止时间: 2011-04-01 至 2014-03-31
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-23370020/
• 关键词: ラジカル酵素; 鉄硫黄クラスター; クロロフィル生合成; 酵素反応; 電子伝達; プロトン移動; 電子スピン共鳴; ニトロゲナーゼ; ラジカル酵素; 鉄硫黄クラスター; クロロフィル生合成; 酵素反応; 電子伝達; プロトン移動; 電子スピン共鳴; ニトロゲナーゼ

In final stages of biosynthesis of Chlorophylls (Chls), dark-operative protochlorophyllide (Pchlide) oxidoreductase (DPOR), a nitrogenase-like enzyme, reduces the C17=C18 double bond of Pchlide to form chlorophyllide, the direct precursor of Chl a. Crystallographic structure of DPOR suggested that the spatial arrangement of the proton donors determines the stereospecificity of the Pchlide reduction. In this study, reaction intermediates were trapped by blocking the proton transfer and they were detected by absorption and electron spin resonance spectroscopies. We proposed that the DPOR reaction consists of 1) generation of a Pchlide anion radical by a single electron transfer reaction from a [4Fe-4S]-cluster to Pchlide, 2) a second Pchlide neutral radical is formed by a single proton transfer, 3) a second electron transfer eliminates the Pchlide radical, and 4) a second proton transfer completes the reaction. DPOR is a unique radical enzyme with a structure common to nitrogenase.

在叶绿素（CHLS）生物合成的最后阶段，深色术原型氯叶酸酯（Pchlide）氧化还原酶（DPOR），一种硝基酶样酶，降低了C17 = C17 = C18双键的C18双键形成氯酸酯的双键，Chlyllide，Chl of Chl a chl a。 DPOR的晶体学结构表明，质子供体的空间排列决定了Pchlide还原的立体特异性。在这项研究中，通过阻断质子转移来捕获反应中间体，并通过吸收和电子自旋共振光谱检测到它们。我们提出，DPOR反应由1）通过单个电子转移反应从[4FE-4S] - 簇到Pchlide的单个电子转移反应，2）第二个Pchlide中性自由基由单个质子传递形成，3）第二电子转移消除了Pchlide自由子的反应。 DPOR是一种独特的自由基酶，其结构是氮气共同的结构。