title: Direct electron transfer of xanthine oxidase and its catalytic reduction to nitrate.
abstract: This work reports on the direct electrochemistry of the xanthine oxidase (XO) from buttermilk, a mononuclear molybdenum enzyme that comprises four redox active cofactors: a five-coordinate mononuclear Mo ion, two [2Fe-2S] clusters, and a flavin adenine dinucleotide (FAD) group. The Mo, [2Fe-2S] and FAD redox responses are obtained from the enzyme immobilized on an activated single-wall carbon nanotubes (SWNTs) modified glassy carbon electrode using protein film voltammetry. The formal potentials of which are -0.61 V, -0.47 V and -0.37 V (vs. SCE) at pH 5.0, respectively. Upon addition of nitrate to the electrochemical cell, a steady-state voltammogram and i-t amprometric response were observed, indicating XO can catalyze the reduction of nitrate.
authors.affiliation: Department of Chemistry, Wuhan University, Wuhan 430072, PR China.
authors.forename: Yunhua
authors.initials: Y
authors.lastname: Wu
authors.forename: Shengshui
authors.initials: S
authors.lastname: Hu
mesh_terms: D000818:Animals; D002384:Catalysis; D002417:Cattle; D004583:Electrons; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D009566:Nitrates / Q000737:chemistry* / Q000378:metabolism*; D010084:Oxidation-Reduction; D014969:Xanthine Oxidase / Q000737:chemistry* / Q000145:classification / Q000378:metabolism*
chemical_list: D009566:Nitrates; D014969:Xanthine Oxidase