IUBMB Enzyme Nomenclature


Accepted name: FAD-dependent urate hydroxylase

Reaction: urate + NADH + H+ + O2 = 5-hydroxyisourate + NAD+ + H2O

Other name(s): HpxO enzyme; FAD-dependent urate oxidase; urate hydroxylase

Systematic name: urate,NADH:oxygen oxidoreductase (5-hydroxyisourate forming)

Comments: A flavoprotein. The reaction is part of the purine catabolic pathway in the bacterium Klebsiella pneumoniae. The enzyme is different from EC, factor-independent urate hydroxylase, found in most plants, which produces hydrogen peroxide. The product of the enzyme is a substrate for EC, hydroxyisourate hydrolase.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number:


1. O'Leary, S.E., Hicks, K.A., Ealick, S.E. and Begley, T.P. Biochemical characterization of the HpxO enzyme from Klebsiella pneumoniae, a novel FAD-dependent urate oxidase. Biochemistry 48 (2009) 3033-3035. [PMID: 19260710]

[EC created 2010]

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