ACTIVATION OF METHIONINE SYNTHASE - FURTHER CHARACTERIZATION OF FLAVOPROTEIN SYSTEM
ACTIVATION OF METHIONINE SYNTHASE - FURTHER CHARACTERIZATION OF FLAVOPROTEIN SYSTEM
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DOI：
10.1016/0003-9861(77)90238-7
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发表时间：
1977-01-01
影响因子：
3.9
通讯作者：
HUENNEKENS, FM
中科院分区：
文献类型：
--
作者：
FUJII, K;GALIVAN, JH;HUENNEKENS, FM
两种均质黄素蛋白（R 和 F 成分）与催化量的 NADPH 和腺苷甲硫氨酸一起构成了激活大肠杆菌 K-12 中含有[维生素] B12 的蛋氨酸合酶 [EC 2.1.1.13]（M 成分）的有效系统，并对其氧化还原性质和参与进行了表征 在激活过程中。 R成分的黄素（FAD）被NADPH还原为FADH2。减少的 R 反过来又将 F 组分的黄素 (FMN) 还原为蓝色半醌 (FMNH.cntdot.)。 R 和 F 的还原电位（pH 7.0 时）分别为 -0.30 和 -0.29 V。其他各种化合物如铁氰化物、2,6-二氯苯酚吲哚酚、甲萘醌和细胞色素c也可以作为还原R的电子受体，但只有F可以有效介导M组分的NADPH和R依赖性激活。激活可能涉及序列：NADPH .fwdarw。 R.fwdarw。 F.fwdarw。 M.在整个系统的运行过程中，消耗的NADPH量<蛋氨酸合成量的2%。
Two homogeneous flavoproteins (R and F components) which, in conjunction with catalytic amounts of NADPH and adenosylmethionine, comprise an efficient system for activation of the [vitamin] B12-containing methionine synthase [EC 2.1.1.13] (M component) from Escherichia coli K-12, were characterized with respect to oxidation-reduction properties and participation in the activation process. The flavin (FAD) of R component is reduced to FADH2 by NADPH. Reduced R, in turn, reduces the flavin (FMN) of F component to a blue semiquinone (FMNH.cntdot.). Reduction potentials (at pH 7.0) for R and F are -0.30 and -0.29 V, respectively. Various other compounds such as ferricyanide, 2,6-dichlorophenolindophenol, menadione and cytochrome c can also serve as electron acceptors for reduced R, but only F can efficiently mediate the NADPH- and R-dependent activation of M component. Activation probably involves the sequence: NADPH .fwdarw. R .fwdarw. F .fwdarw. M. During operation of the complete system, the amount of NADPH consumed is < 2% of the amount of methionine synthesized.