ABSTRACTA hydrophobic, redox-active component with a molecular mass of 538 Da was isolated from lyophilized membranes ofMethanosarcina mazeiGö1 by extraction with isooctane. After purification on a high-performance liquid chromatography column, the chemical structure was analyzed by mass spectroscopy and nuclear magnetic resonance studies. The component was called methanophenazine and represents a 2-hydroxyphenazine derivative which is connected via an ether bridge to a polyisoprenoid side chain. Since methanophenazine was almost insoluble in aqueous buffers, water-soluble phenazine derivatives were tested for their ability to interact with membrane-bound enzymes involved in electron transport and energy conservation. The purified F420H2dehydrogenase fromM. mazeiGö1 showed highest activity with 2-hydroxyphenazine and 2-bromophenazine as electron acceptors when F420H2was added. Phenazine-1-carboxylic acid and phenazine proved to be less effective. TheKmvalues for 2-hydroxyphenazine and phenazine were 35 and 250 μM, respectively. 2-Hydroxyphenazine was also reduced by molecular hydrogen catalyzed by an F420-nonreactive hydrogenase which is present in washed membrane preparations. Furthermore, the membrane-bound heterodisulfide reductase was able to use reduced 2-hydroxyphenazine as an electron donor for the reduction of CoB-S-S-CoM. Considering all these results, it is reasonable to assume that methanophenazine plays an important role in vivo in membrane-bound electron transport ofM. mazeiGö1.
摘要:通过异辛烷萃取,从冻干的Methanosarcina mazeiGö1 膜中分离出一种疏水性氧化还原活性成分,其分子质量为 538 Da。经高效液相色谱柱纯化后,通过质谱和核磁共振研究分析了其化学结构。这种成分被称为甲吩嗪,是一种 2-羟基吩嗪衍生物,通过醚桥与多异戊烯侧链相连。由于甲基吩嗪几乎不溶于水性缓冲液,因此我们测试了水溶性吩嗪衍生物与参与电子传递和能量守恒的膜结合酶相互作用的能力。从 M. mazeiGö1 中纯化的 F420H2 脱氢酶在加入 2-羟基吩嗪和 2-溴吩嗪作为电子受体时显示出最高的活性。酚嗪-1-羧酸和酚嗪的活性较低。2- 羟基哒嗪和吩嗪的 Km 值分别为 35 μM 和 250 μM。2- 羟基哒嗪也在一种 F420 非反应性氢化酶的催化下被分子氢还原,这种氢化酶存在于洗膜制备物中。此外,膜结合的杂二硫还原酶能够利用还原的 2-羟基哒嗪作为电子供体,还原 CoB-S-S-CoM。考虑到所有这些结果,我们有理由推测甲氧苄肼在马泽Gö1的膜结合电子传递过程中发挥了重要作用。