Urate oxidase 1081554 181499565 2008-01-02T02:08:52Z Drphilharmonic 704902 logic {{protein | Name = urate oxidase | caption = | image = | width = | HGNCid = 12575 | Symbol = UOX | AltSymbols = | EntrezGene = 7377 | OMIM = 191540 | RefSeq = | UniProt = | PDB = | ECnumber = 1.7.3.3 | Chromosome = 1 | Arm = p | Band = 22 | LocusSupplementaryData = }} The enzyme '''urate oxidase''', or '''UO''', (''[[Aspergillus flavus]]'' enzyme {{PDB|1R4U}}, {{EC number|1.7.3.3}}) catalyzes the [[oxidation]] of [[uric acid]] to [[5-hydroxyisourate]]. :Uric acid + O<sub>2</sub> + H<sub>2</sub>O &rarr; 5-hydroxyisourate + [[hydrogen peroxide|H<sub>2</sub>O<sub>2</sub>]]&rarr; allantoin + CO<sub>2</sub> ==Structure== Urate oxidase is a [[homotetrameric]] enzyme containing four identical active sites situated at the interfaces between its four subunits. UO from A. flavus is made up of 301 residues and has a molecular weight of 33438 [[dalton (unit)|dalton]]. It is unique among the [[oxidase]] in that it does not require a metal atom or an organic co-factor for [[catalysis]]. ==Significance of absence in humans== [[Image:Uric acid.png|thumb|[[Uric acid]]]] While UO can be found in an extensive variety of organisms, from [[bacteria]] to [[mammals]], and plays different metabolic roles, depending on its host organism, its expression is absent in humans and many [[primates]]. However, humans do have the [[gene]] for UO, but it is nonfunctional, a consequence purported to be due to an occurrence of a sudden mutational event early in primate [[evolution]]. Uric acid is, thus, the final step in the [[catabolism]] of [[purine]]s in humans. It has also been proposed that the loss of this UO [[protein expression]] has been advantageous to hominoids, since uric acid is a powerful [[antioxidant]] and scavenger of singlet oxygen and [[Radical (chemistry)|radical]]s. Its presence provides the body with protection from [[oxidative]] damage, thus prolonging life and decreasing age-specific cancer rates. Excessive concentrations of uric acid accumulated in the blood stream, however, leads to [[gout]]. UO has been formulated for the treatment of acute hyperuricaemia as a protein drug (non-proprietary drug name ''[[rasburicase]]'') in patients receiving chemotherapy. A PEGylated form of UO is in clinical development for treatment of chronic hyperuricemia in patients with "treatment-failure gout." ==In legumes== UO is also an essential enzyme in the ureide pathway, where [[nitrogen fixation]] occurs in the root nodules of [[legume]]s. The fixed nitrogen is converted to [[metabolite]]s that are transported from the roots throughout the plant to provide the needed nitrogen for [[amino acid]] biosynthesis. {{Nitrogenous donor oxidoreductases}} {{Nucleotide metabolism}} [[Category:EC 1.7.3]] [[de:Uricase]] [[it:Urato ossidasi]]