13C and 63,65Cu ENDOR studies of CO Dehydrogenase from Oligotropha carboxidovorans. Experimental Evidence in Support of a Copper鈥揅arbonyl Intermediate

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• 作者：Muralidharan Shanmugam ; Jarett Wilcoxen ; Diana Habel-Rodriguez ; George E. Cutsail III ; Martin L. Kirk ; Brian M. Hoffman ; Russ Hille
• 刊名：Journal of the American Chemical Society
• 出版年：2013
• 出版时间：November 27, 2013
• 年：2013
• 卷：135
• 期：47
• 页码：17775-17782
• 全文大小：406K
• 年卷期：v.135,no.47(November 27, 2013)
• ISSN：1520-5126

文摘

We report here an ENDOR study of an S = 1/2 intermediate state trapped during reduction of the binuclear Mo/Cu enzyme CO dehydrogenase by CO. ENDOR spectra of this state confirm that the ^63,65Cu nuclei exhibits strong and almost entirely isotropic coupling to the unpaired electron, show that this coupling atypically has a positive sign, a_iso = +148 MHz, and indicate an apparently undetectably small quadrupolar coupling. When the intermediate is generated using ¹³CO, coupling to the ¹³C is observed, with a_iso = +17.3 MHz. A comparison with the couplings seen in related, structurally assigned Mo(V) species from xanthine oxidase, in conjunction with complementary computational studies, leads us to conclude that the intermediate contains a partially reduced Mo(V)/Cu(I) center with CO bound at the copper. Our results provide strong experimental support for a reaction mechanism that proceeds from a comparable complex of CO with fully oxidized Mo(VI)/Cu(I) enzyme.