title: (13)C and (63,65)Cu ENDOR studies of CO dehydrogenase from Oligotropha carboxidovorans. Experimental evidence in support of a copper-carbonyl intermediate.
abstract: 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 (63,65)Cu nuclei exhibits strong and almost entirely isotropic coupling to the unpaired electron, show that this coupling atypically has a positive sign, aiso = +148 MHz, and indicate an apparently undetectably small quadrupolar coupling. When the intermediate is generated using (13)CO, coupling to the (13)C is observed, with aiso = +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.
authors.affiliation: Department of Chemistry, Northwestern University , Evanston, Illinois 60208-3113, United States.
authors.forename: Muralidharan
authors.initials: M
authors.lastname: Shanmugam
authors.forename: Jarett
authors.initials: J
authors.lastname: Wilcoxen
authors.forename: Diana
authors.initials: D
authors.lastname: Habel-Rodriguez
authors.forename: George E
authors.initials: GE
authors.lastname: Cutsail
authors.forename: Martin L
authors.initials: ML
authors.lastname: Kirk
authors.forename: Brian M
authors.initials: BM
authors.lastname: Hoffman
authors.forename: Russ
authors.initials: R
authors.lastname: Hille
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D020561:Alphaproteobacteria / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D020134:Catalytic Domain; D003300:Copper / Q000737:chemistry / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D008958:Models, Molecular; D009097:Multienzyme Complexes / Q000737:chemistry / Q000378:metabolism*
chemical_list: D009097:Multienzyme Complexes; D003300:Copper; D000445:Aldehyde Oxidoreductases; C019823:carbon monoxide dehydrogenase