THE VANADIUM NITROGENASE OF AZOTOBACTER-CHROOCOCCUM - REDUCTION OF ACETYLENE AND ETHYLENE TO ETHANE
THE VANADIUM NITROGENASE OF AZOTOBACTER-CHROOCOCCUM - REDUCTION OF ACETYLENE AND ETHYLENE TO ETHANE
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DOI：
10.1042/bj2490745
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发表时间：
1988-02-01
影响因子：
4.1
通讯作者：
ELDRIDGE, ME
中科院分区：
文献类型：
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作者：
DILWORTH, MJ;EADY, RR;ELDRIDGE, ME
1.固氮菌的钒（V-）固氮酶转移了7.4%的乙炔（C2 H2）还原形成乙烷（C2 H6）的电子。C2 H2（6 kPa）的表观Km对于乙烯（C2 H4）或乙烷（C2 H6）的形成是相同的，并且远高于报道的钼（Mo-）固氮酶将C2 H2还原成C2 H4的Km值。在2 H2O中还原C2 H2主要产生[Cis-2 H2]乙烯。2.产生C2 H6的电子通量与产生C2 H4的电子通量的比率（C2 H6/C2 H4比率）通过提高Fe蛋白与VFe蛋白的比率和通过将测定温度提高到至少40 ℃而提高。C. pH值高于7.5会降低C2 H6/C2 H4比率。3.由C2 H2通过V-固氮酶形成C2 H4和C2 H6不受H2抑制。CO对这两个过程的抑制作用远小于对Mo-固氮酶催化C_2H_2生成C_2H_4的抑制作用。4.虽然V-固氮酶也催化C4 H4到C2 H6的缓慢CO敏感还原，但游离C2 H4不是从C2 H2形成C2 H6的中间体。5.丙炔（CH 3 C. CH）不被V-固氮酶还原。6.这些结果的机制C2 H6形成的V-固氮酶的一些影响进行了讨论。
1. The vanadium (V-) nitrogenase of Azobacter chroococcum transfers up to 7.4% of the electrons used in acetylene (C2H2) reduction for the formation of ethane (C2H6). The apparent Km for C2H2 (6 kPa) is the same for either ethylene (C2H4) or ethane (C2H6) formation and much higher than the reported Km values for C2H2 reduction to C2H4 by molybdenum (Mo-) nitrogenases. Reduction of C2H2 in 2H2O yields predominantly [Cis-2H2]ethylene. 2. The ratio of electron flux yieding C2H6 to that yielding C2H4 (the C2H6/C2H4 ratio) is increased by rasing the ratio of Fe protein to VFe protein and by increasing the assay temperature up to at least 40.degree. C. pH values above 7.5 decrease the C2H6/C2H4 ratio. 3. C2H4 and C2H6 formation from C2H2 by V-nitrogenase are not inhibited by H2. CO inhibits both processes much less storngly than in inhibits C2H4 formation from C2H2 with Mo-nitrogenase. 4. Although V-nitrogenase also catalyses the slow CO-sensitive reduction of C4H4 to C2H6, free C2H4 is not an intermediate in C2H6 formation from C2H2. 5. Propyne (CH3 C .tbd. CH) is not reduced by the V-nitrogenase. 6. Some implications of these results for the mechanism of C2H6 formation by the V-nitrogenase are discussed.