The Structure of Formaldehyde-Inhibited Xanthine Oxidase Determined by 35 GHz 2H ENDOR Spectroscopy

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• 作者：Muralidharan Shanmugam ; Bo Zhang ; Rebecca L. McNaughton ; R. Adam Kinney ; Russ Hille ; Brian M. Hoffman
• 刊名：Journal of the American Chemical Society
• 出版年：2010
• 出版时间：October 13, 2010
• 年：2010
• 卷：132
• 期：40
• 页码：14015-14017
• 全文大小：152K
• 年卷期：v.132,no.40(October 13, 2010)
• ISSN：1520-5126

文摘

The formaldehyde-inhibited Mo(V) state of xanthine oxidase (I) has been studied for four decades, yet it has not proven possible to distinguish unequivocally among the several structures proposed for this form. The uniquely large isotropic hyperfine coupling for ¹³C from CH₂O led to the intriguing suggestion of a direct Mo−C bond for the active site of I. This suggestion was supported by the recent crystal structures of glycol- and glycerol-inhibited forms of aldehyde oxidoreductase, a member of the xanthine oxidase family. ¹H and ²H ENDOR spectra of I(C^1,2H₂O) in H₂O/D₂O buffer now have unambiguously revealed that the active-site structure of I contains a CH₂O adduct of Mo(V) in the form of a four-membered ring with S and O linking the C to Mo and have ruled out a direct Mo−C bond. Density functional theory computations are consistent with this conclusion. We interpret the large ¹³C coupling as resulting from a “transannular hyperfine interaction”.