Higuchi Y, Yagi T
Graduate School of Science, Kyoto University, Japan.
Biochem Biophys Res Commun. 1999 Feb 16;255(2):295-9. doi: 10.1006/bbrc.1999.0210.
The active site of [NiFe] hydrogenase from Desulfovibrio species is composed of a binuclear Ni-Fe complex bearing three diatomic nonprotein ligands to Fe and three bridges between the two metals, two of which are thiolate side chains of the protein moiety. The third bridging atom in the enzyme isolated from D. vulgaris Miyazaki F was suggested to be sulfur species, but was suggested to be oxygen species in D. gigas enzyme. When the hydrogenase from D. vulgaris Miyazaki F was incubated under the atmosphere of H2, H2S was liberated from the enzyme only in the presence of its electron carrier, cytochrome c3 or methylviologen. The amount of H2S liberation was little in the absence of electron carrier or essentially null when the enzyme was incubated under N2. The amount of H2S liberated was about 37% of the hydrogenase contained in the reaction vial in molar basis. These observations are in agreement with the recent observation that the third bridging site at the Ni-Fe active site is vacant in the reduced form of the enzyme revealed by X-ray crystallography.
脱硫弧菌属的[NiFe]氢化酶的活性位点由一个双核Ni-Fe络合物组成，该络合物带有三个与铁结合的双原子非蛋白质配体以及两个金属之间的三个桥，其中两个是蛋白质部分的硫醇盐侧链。从宫崎F型普通脱硫弧菌分离出的酶中的第三个桥连原子被认为是硫物种，但在巨大脱硫弧菌的酶中被认为是氧物种。当宫崎F型普通脱硫弧菌的氢化酶在H₂气氛中孵育时，只有在其电子载体细胞色素c3或甲基紫精存在的情况下，H₂S才会从酶中释放出来。在没有电子载体的情况下，H₂S的释放量很少，或者当酶在N₂下孵育时基本上为零。以摩尔计，释放的H₂S量约为反应瓶中氢化酶含量的37%。这些观察结果与最近的观察结果一致，即X射线晶体学显示，在酶的还原形式中，Ni-Fe活性位点的第三个桥连位点是空的。
