title: Biochemical characterization of the HpxO enzyme from Klebsiella pneumoniae, a novel FAD-dependent urate oxidase.
abstract: The HpxO enzyme from Klebsiella pneumoniae was recently proposed, on the basis of genetic studies, to catalyze the hydroxylation of uric acid to 5-hydroxyisourate as part of the purine catabolic pathway. Its primary sequence suggests that the HpxO catalytic activity depends on a flavin cofactor (FAD), contrasting with all previously studied urate oxidase enzymes, which have no cofactor requirement. Here we demonstrate biochemically that HpxO is an FAD-dependent urate oxidase. Our data are consistent with the proposal that HpxO-bound flavin hydroperoxide is the hydroxylating species. These results confirm the existence of a novel mechanistic paradigm in purine catabolism.
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301, USA.
authors.forename: Seán E
authors.initials: SE
authors.lastname: O'Leary
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Hicks
authors.forename: Steven E
authors.initials: SE
authors.lastname: Ealick
authors.forename: Tadhg P
authors.initials: TP
authors.lastname: Begley
mesh_terms: D005182:Flavin-Adenine Dinucleotide; D006900:Hydroxylation; D007711:Klebsiella pneumoniae / Q000201:enzymology*; D011687:Purines / Q000378:metabolism; D014503:Urate Oxidase / Q000737:chemistry* / Q000378:metabolism; D014527:Uric Acid / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: C510200:5-hydroxyisourate; D011687:Purines; D005182:Flavin-Adenine Dinucleotide; D014527:Uric Acid; D014503:Urate Oxidase