Siebert Anke, Schubert Torsten, Engelmann Tina, Studenik Sandra, Diekert Gabriele
Institut für Mikrobiologie, FSU Jena, Lehrstuhl für Angewandte und Okologische Mikrobiologie, Philosophenweg 12, 07743 Jena, Germany.
Arch Microbiol. 2005 Sep;183(6):378-84. doi: 10.1007/s00203-005-0001-8. Epub 2005 Oct 13.
The anaerobic veratrol O-demethylase mediates the transfer of the methyl group of the phenyl methyl ether veratrol to tetrahydrofolate. The primary methyl group acceptor is the cobalt of a corrinoid protein, which has to be in the +1 oxidation state to bind the methyl group. Due to the negative redox potential of the cob(II)/cob(I)alamin couple, autoxidation of the cobalt may accidentally occur. In this study, the reduction of the corrinoid to the superreduced [Co(I)] state was investigated. The ATP-dependent reduction of the corrinoid protein of the veratrol O-demethylase was shown to be dependent on titanium(III) citrate as electron donor and on an activating enzyme. In the presence of ATP, activating enzyme, and Ti(III), the redox potential versus the standard hydrogen electrode (E (SHE)) of the cob(II)alamin/cob(I)alamin couple in the corrinoid protein was determined to be -290 mV (pH 7.5), whereas E (SHE) at pH 7.5 was lower than -450 mV in the absence of either activating enzyme or ATP. ADP, AMP, or GTP could not replace ATP in the activation reaction. The ATP analogue adenosine-5'-(beta,gamma-imido)triphosphate (AMP-PNP, 2-4 mM) completely inhibited the corrinoid reduction in the presence of ATP (2 mM).
厌氧藜芦醇O - 脱甲基酶介导苯甲基醚藜芦醇的甲基转移至四氢叶酸。主要的甲基受体是类咕啉蛋白的钴，其必须处于 +1氧化态才能结合甲基。由于钴（II）/钴（I）钴胺素偶联物的负氧化还原电位，钴可能会意外发生自氧化。在本研究中，对类咕啉还原为超还原态[Co（I）]进行了研究。结果表明，藜芦醇O - 脱甲基酶的类咕啉蛋白的ATP依赖性还原依赖于柠檬酸钛（III）作为电子供体和一种激活酶。在ATP、激活酶和Ti（III）存在的情况下，类咕啉蛋白中钴胺素（II）/钴胺素（I）偶联物相对于标准氢电极（E（SHE））的氧化还原电位测定为 -290 mV（pH 7.5），而在没有激活酶或ATP的情况下，pH 7.5时的E（SHE）低于 -450 mV。ADP、AMP或GTP不能在激活反应中替代ATP。ATP类似物腺苷 -5'-（β，γ-亚氨基）三磷酸（AMP - PNP，2 - 4 mM）在ATP（2 mM）存在时完全抑制类咕啉还原。
