ARSENITE-INHIBITED XANTHINE-OXIDASE - DETERMINATION OF THE MO-S-AS GEOMETRY BY EXAFS
ARSENITE-INHIBITED XANTHINE-OXIDASE - DETERMINATION OF THE MO-S-AS GEOMETRY BY EXAFS
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DOI：
10.1021/ja00312a059
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发表时间：
1985-12-25
影响因子：
15
通讯作者：
HILLE, R
中科院分区：
文献类型：
--
作者：
CRAMER, SP;HILLE, R
在砷和钼的K边上研究了亚砷酸盐与氧化的、部分还原的和完全还原的黄嘌呤氧化酶的相互作用。在完全还原的三元络合物的钼EXAFS中观察到3.00 ANGMo-As相互作用的明显证据，该三元络合物由黄嘌呤氧化酶、亚砷酸盐和抑制剂8-溴黄嘌呤组成。Mo(V)络合物的本质相同的Mo-As距离为3.02。预计报告距离的准确性为.+-。0.03ANG.对于第一配位球键和.+-。0.05。ANG.用于长时间互动。令人惊讶的是，无论是从钼还是从砷的角度来看，在氧化酶的EXAFS中没有观察到可归因于Mo-As相互作用的明显特征。此外，当8-溴黄嘌呤存在时，没有观察到钼-溴相互作用。对于氧化的黄嘌呤氧化酶，末端为Mo.O和Mo.dbd.在亚砷酸盐络合物和对照样品中，S键的距离分别为1.63和2.15，而对照样品的距离分别为1.67和2.15。在亚砷酸盐抑制的样品和对照样品中，分别在2.43和2.44 ANG.处发现了另外一组类似硫代的亮氨酸。对于氧化的亚砷酸盐络合物，砷的EXAFS表明它与三个氧配体结合，平均AS-O距离为1.78。在完全还原的亚砷酸盐和8-溴黄嘌呤的络合物中，一个短的Mo.观察到O键的长度为1.69°，与Mo.DBd相当。在未络合的还原酶中O距离为1.67。在这两种情况下，终端MO.数据库。S的互动不再明显。在还原和还原三元络合物数据中，分别在2.38和2.39°的平均距离处观察到三个硫原子最适合的强Mo-S相互作用。对于后一种络合物，根据砷的EXAFS计算出的As-S距离为2.27ANG.，对应于至少一个且更可能是两个As-S相互作用。在1.78 nm处还观察到弱的As-O相互作用。假设Mo-S-为键，且.+-。EXAFS显示的距离的准确度为0.05，Mo-S-AS角为80。+-。4.学位。可以派生出来。
The interaction of arsenite with oxidized, partially reduced, and fully reduced forms of xanthine oxidase has been studied X-ray absorption spectroscopy at the arsenic and molybedenum K edges. Clear evidence for a Mo-As interaction at 3.00 .ANG. is observed in the molybdenum EXAFS of the fully reduced ternary complex consisting of xanthine oxidase, arsenite, and the inhibitor 8-bromoxanthine. An essential identical Mo-As distance of 3.02 .ANG. was found for the Mo(V) complex. The accuracy of distances reported is expected to be .+-. 0.03 .ANG. for first coordination sphere bonds and .+-. 0.05 .ANG. for long interactions. Suprisingly, no distinct features attributable to a Mo-As interaction are observed in the EXAFS of the oxidized enzyme, from either the molybdenum or the arsenic point of view. Furthermore, no Mo-Br interaction was observed when 8-bromoxanthine was present. For oxidized xanthine oxidase, terminal Mo .dbd. O and Mo .dbd. S bonds were observed at distances of 1.63 and 2.15 .ANG. in the arsenite complex and 1.67 and 2.15 .ANG. in the control sample. An additional set of thiolate like legands was found at 2.43 and 2.44 .ANG. in the arsenite-inhibited and control samples, respectively. For the oxidized arsenite complex, the arsenic EXAFS suggested binding by three oxygen ligands with an average As-O distance of 1.78 .ANG.. In the fully-reduced arsenite plus 8-bromoxanthine complex, a short Mo .dbd. O bond with a length of 1.69 .ANG. was observed, comparable to the Mo .dbd. O distance of 1.67 .ANG. in the uncomplexed reduced enzyme. In both cases, terminal Mo .dbd. S interactions were no longer evident. A strong Mo-S interaction, best fit by three sulfurs, was observed at average distances of 2.38 and 2.39 .ANG. in the reduced and reduced-ternary complex data, respectively. For the latter complex, an As-S distance of 2.27 .ANG. was calculated from the arsenic EXAFS, corresponding to at least one and more likely two As-S interactions. A weak As-O interaction at 1.78 .ANG. was also observed. Assuming Mo-S-As bonding, and .+-. 0.05 .ANG. accuracy for the distances revealed by EXAFS, a Mo-S-As angle of 80 .+-. 4.degree. can be derived.