title: Purification, crystallization and preliminary X-ray diffraction studies of xanthine dehydrogenase and xanthine oxidase isolated from bovine milk.
abstract: Xanthine dehydrogenase catalyzes the oxidation of hypoxanthine to xanthine and the further oxidation of xanthine to uric acid. The enzyme is the target of the anti-gout drug allopurinol and its involvement in postischemic reperfusion injury is presently being defined. Each subunit of the homodimeric 290 kDa enzyme contains four cofactors: one Mo-pterin, two [2Fe-2S] clusters and one FAD. Both the dehydrogenase (XDH) and the proteolytically modified oxidase form (XO) of the enzyme from bovine milk have been crystallized. XO crystals belong to space group C222(1), with unit-cell parameters a = 116.3, b = 164.4, c = 153.2 A at room temperature and a = 117.8, b = 165.4, c = 154.5 A when flash-frozen. They allow data collection to 3.3 and 2.5 A, respectively. In addition, a data set was collected from frozen XDH crystals and processed to 2.1 A. These crystals belong to space group C2, with unit-cell parameters a = 169.9, b = 124.8, c = 148.6 A, beta = 90.9 degrees. The unit-cell volumes and Matthews parameters are similar for the two crystal forms. There is one monomer per asymmetric unit in the XO crystals and a complete native dimer per asymmetric unit in the XDH crystals.
authors.affiliation: University of Toronto, Department of Biochemistry, 1 Kings College Circle, Toronto, Ontario M5S 1A8, Canada.
authors.forename: B T
authors.initials: BT
authors.lastname: Eger
authors.forename: K
authors.initials: K
authors.lastname: Okamoto
authors.forename: C
authors.initials: C
authors.lastname: Enroth
authors.forename: M
authors.initials: M
authors.lastname: Sato
authors.forename: T
authors.initials: T
authors.lastname: Nishino
authors.forename: E F
authors.initials: EF
authors.lastname: Pai
authors.forename: T
authors.initials: T
authors.lastname: Nishino
mesh_terms: D000818:Animals; D018360:Crystallography, X-Ray; D008892:Milk / Q000201:enzymology*; D011487:Protein Conformation; D014968:Xanthine Dehydrogenase / Q000737:chemistry* / Q000302:isolation & purification; D014969:Xanthine Oxidase / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D014968:Xanthine Dehydrogenase; D014969:Xanthine Oxidase