HYDRAZINE IS A PRODUCT OF DINITROGEN REDUCTION BY THE VANADIUM-NITROGENASE FROM AZOTOBACTER-CHROOCOCCUM
HYDRAZINE IS A PRODUCT OF DINITROGEN REDUCTION BY THE VANADIUM-NITROGENASE FROM AZOTOBACTER-CHROOCOCCUM
复制标题
DOI：
10.1042/bj2770465
复制
发表时间：
1991-07-15
影响因子：
4.1
通讯作者：
EADY, RR
中科院分区：
文献类型：
--
作者：
DILWORTH, MJ;EADY, RR
在通过Mo-固氮酶将N2酶促还原为NH3的过程中，游离肼（N2 H4）是不可检测的，但是可以通过在周转过程中淬灭酶来制备酶结合的中间体以产生N2 H4 [Thorneley，Eady & Lowe（1978）Nature（伦敦）272，557-558]。相比之下，我们在这里表明，固氮菌chroococcum的V-固氮酶产生一个小的，但显着量的游离N2 H4（高达0.5%的电子通量导致N2还原）作为产品的N2还原。当测定温度从20 ℃增加到40 ℃时，形成的N2 H4的量增加了15倍。Mo-和V-固氮酶的固氮酶组分之间的活性交叉反应表明，游离N_2H_4的形成与VFe蛋白有关。这些数据提供了第一个直接的证据，在四电子还原的水平上的酶中间体在还原N2的V-固氮酶。
During the enzymic reduction of N2 to NH3 by Mo-nitrogenase, free hydrazine (N2H4) is not detectable, but an enzyme-bound intermediate can be made to yield N2H4 by quenching the enzyme during turnover [Thorneley, Eady & Lowe (1978) Nature (London) 272, 557-558]. In contrast, we show here that the V-nitrogenase of Azotobacter chroococcum produces a small but significant amount of free N2H4 (up to 0.5% of the electron flux resulting in N2 reduction) as a product of the reduction of N2. The amount of N2H4 formed increased 15-fold on increasing the assay temperature from 20-degrees-C to 40-degrees-C. Activity cross-reactions between nitrogenase components of Mo- and V-nitrogenases showed that the formation of free N2H4 was associated with the VFe protein. These data provide the first direct evidence for an enzyme intermediate at the four-electron-reduced level during the reduction of N2 by V-nitrogenase.