Kaufmann F, Wohlfarth G, Diekert G
Institut für Mikrobiologie der Universität Stuttgart, Germany.
Eur J Biochem. 1998 May 1;253(3):706-11. doi: 10.1046/j.1432-1327.1998.2530706.x.
The ether-cleaving O-demethylase isolated from syringate-grown cells of Acetobacterium dehalogenans (formerly named strain MC) consists of four proteins, components A, B, C and D. The enzyme system converts only phenyl methyl ethers with a hydroxyl group in the ortho position to the methoxyl moiety. The presence of a carboxyl group in the aromatic compound was not required for O-demethylase reaction. Component B mediated the conversion of vanillate to 3,4-dihydroxybenzoate in the presence of the Ti(III)-reduced corrinoid-containing component A. After addition of component D and tetrahydrofolate, methyl tetrahydrofolate was formed from vanillate in stoichiometric amounts. Titanium(III) citrate as a reductant could be replaced by H2, methyl viologen or ferredoxin, partially purified hydrogenase, purified component C obtained from A. dehalogenans, and ATP. From these findings, it was deduced that component B serves as vanillate:corrinoid protein methyltransferase (methyltransferase I) mediating the methyl transfer from vanillate to the reduced corrinoid protein component A. Component D functions as methylcorrinoid protein:tetrahydrofolate transferase (methyltransferase II). The role of component C is probably that of an activating protein reversing accidental oxidation of the protein-bound cob(I)alamin to cob(II)alamin in the presence of ATP and reducing equivalents supplied by the enzymatic oxidation of hydrogen.
从脱卤产乙酸菌（原名为菌株MC）丁香酸培养细胞中分离出的醚裂解O - 脱甲基酶由四种蛋白质组成，即组分A、B、C和D。该酶系统仅能将在甲氧基部分邻位带有羟基的苯基甲基醚进行转化。O - 脱甲基酶反应并不需要芳香族化合物中存在羧基。在含有经Ti(III)还原的类咕啉的组分A存在时，组分B介导香草酸转化为3,4 - 二羟基苯甲酸。加入组分D和四氢叶酸后，香草酸能按化学计量生成甲基四氢叶酸。柠檬酸钛作为还原剂可被氢气、甲基紫精或铁氧化还原蛋白、部分纯化的氢化酶、从脱卤产乙酸菌中获得的纯化组分C以及ATP替代。基于这些发现，推断组分B作为香草酸：类咕啉蛋白甲基转移酶（甲基转移酶I），介导从香草酸到还原的类咕啉蛋白组分A的甲基转移。组分D作为甲基类咕啉蛋白：四氢叶酸转移酶（甲基转移酶II）。组分C的作用可能是一种激活蛋白，在ATP以及由氢气酶促氧化提供的还原当量存在的情况下，逆转蛋白质结合的钴胺素（I）偶然氧化为钴胺素（II）。
