George G N, Kipke C A, Prince R C, Sunde R A, Enemark J H, Cramer S P
Exxon Research and Engineering Company, Annandale, New Jersey 08801.
Biochemistry. 1989 Jun 13;28(12):5075-80. doi: 10.1021/bi00438a026.
The active site of sulfite oxidase has been investigated by X-ray absorption spectroscopy at the molybdenum K-edge at 4 K. We have investigated all three accessible molybdenum oxidation states, Mo(IV), Mo(V), and Mo(VI), allowing comparison with the Mo(V) electron paramagnetic resonance data for the first time. Quantitative analysis of the extended X-ray absorption fine structure indicates that the Mo(VI) oxidation state possesses two terminal oxo (Mo = O) and approximately three thiolate-like (Mo-S-) ligands and is unaffected by changes in pH and chloride concentration. The Mo(IV) and Mo(V) oxidation states, however, each have a single oxo ligand plus one Mo-O- (or Mo-N less than) bond, most probably Mo--OH, and two to three thiolate-like ligands. Both reduced forms appear to gain a single chloride ligand under conditions of low pH and high chloride concentration.
通过在4K下钼K边的X射线吸收光谱研究了亚硫酸盐氧化酶的活性位点。我们研究了所有三种可及的钼氧化态，即Mo(IV)、Mo(V)和Mo(VI)，首次能够与Mo(V)的电子顺磁共振数据进行比较。对扩展X射线吸收精细结构的定量分析表明，Mo(VI)氧化态具有两个端基氧（Mo=O）和大约三个硫醇盐样（Mo-S-）配体，并且不受pH值和氯离子浓度变化的影响。然而，Mo(IV)和Mo(V)氧化态各自具有一个单氧配体加上一个Mo-O-（或小于Mo-N）键，很可能是Mo--OH，以及两到三个硫醇盐样配体。在低pH和高氯离子浓度条件下，两种还原态似乎都获得了一个单氯离子配体。
