The process of metabolizing purines to a common molecule known as xanthine is an essential process for the proper shuttling of uric acid. Xanthine oxidase is a flavoprotein enzyme that coordinates molybdenum and utilizes NAD+ as an electron acceptor to catalyze the oxidation of hypoxanthine to xanthine and then to uric acid. The predominant form of this enzyme is xanthine dehydrogenase, which is a homodimer that can be converted to xanthine oxidase by sulfhydryl oxidation or proteolytic modification. Xanthine oxidase is present in species ranging from bacteria to human and is ubiquitously expressed in mammalian tissues. In the oxidase form, this enzyme is coupled to the generation of free radicals. Individuals showing marked elevation of serum xanthine oxidase is suggestive of chronic liver disease and cholestasis, which is a condition defined by hepatic obstruction. Hepatic obstruction causes bile salts, the bile pigment bilirubin, and fats to accumulate in the blood stream instead of being eliminated normally. The clinical consequences of defects in xanthine oxidase range from mild to severe and even contribute to fatal disorders.
Background References
1. Yamaguchi Y et al. Human xanthine oxidase changes its substrate specificity to aldehyde oxidase type upon mutation of amino acid residues in the active site: roles of active site residues in binding and activation of purine substrate. J Biochem 141:513-524 (2007).
2. Saksela M et al. Cloning and expression in vitro of human xanthine dehydrogenase/oxidase. Biochem J 315:235-239 (1996).
Sequence Similarity
Belongs to the xanthine dehydrogenase family.
Tissue Specificity
Detected in milk (at protein level).
Post-translational Modification
Subject to partial proteolysis; this alters the enzyme from the dehydrogenase form (D) to the oxidase form (O).; Contains sulfhydryl groups that are easily oxidized (in vitro); this alters the enzyme from the dehydrogenase form (D) to the oxidase form (O).
Western blot analysis of Xanthine Oxidase on different lysates with Rabbit anti-Xanthine Oxidase antibody (ET7108-69) at 1/1,000 dilution.
Lane 1: Human liver tissue lysate Lane 2: Mouse liver tissue lysate Lane 3: Rat liver tissue lysate
Lysates/proteins at 20 µg/Lane.
Predicted band size: 146 kDa Observed band size: 146 kDa
Exposure time: Lane 1: 1 minute 2 seconds; Lane 2-3: 4 seconds; ECL: K1801;
4-20% SDS-PAGE gel.
Proteins were transferred to a PVDF membrane and blocked with 5% NFDM/TBST for 1 hour at room temperature. The primary antibody (ET7108-69) at 1/1,000 dilution was used in 5% NFDM/TBST at 4℃ overnight. Goat Anti-Rabbit IgG - HRP Secondary Antibody (HA1001) at 1/50,000 dilution was used for 1 hour at room temperature.
Immunohistochemical analysis of paraffin-embedded human liver tissue using anti-Xanthine Oxidase antibody. The section was pre-treated using heat mediated antigen retrieval with Tris-EDTA buffer (pH 9.0) for 20 minutes.The tissues were blocked in 1% BSA for 30 minutes at room temperature, washed with ddH2O and PBS, and then probed with the primary antibody (ET7108-69, 1/50) for 30 minutes at room temperature. The detection was performed using an HRP conjugated compact polymer system. DAB was used as the chromogen. Tissues were counterstained with hematoxylin and mounted with DPX.
Immunohistochemical analysis of paraffin-embedded mouse liver tissue using anti-Xanthine Oxidase antibody. The section was pre-treated using heat mediated antigen retrieval with Tris-EDTA buffer (pH 9.0) for 20 minutes.The tissues were blocked in 1% BSA for 30 minutes at room temperature, washed with ddH2O and PBS, and then probed with the primary antibody (ET7108-69, 1/50) for 30 minutes at room temperature. The detection was performed using an HRP conjugated compact polymer system. DAB was used as the chromogen. Tissues were counterstained with hematoxylin and mounted with DPX.
Immunohistochemical analysis of paraffin-embedded rat liver tissue using anti-Xanthine Oxidase antibody. The section was pre-treated using heat mediated antigen retrieval with Tris-EDTA buffer (pH 9.0) for 20 minutes.The tissues were blocked in 1% BSA for 30 minutes at room temperature, washed with ddH2O and PBS, and then probed with the primary antibody (ET7108-69, 1/50) for 30 minutes at room temperature. The detection was performed using an HRP conjugated compact polymer system. DAB was used as the chromogen. Tissues were counterstained with hematoxylin and mounted with DPX.
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