Chonnam Med J.  2001 Dec;37(4):357-365.

Xanthine Oxidase Stimulates the Enzyme Inactivation by Metal-Catalyzed Oxidation Systems

• Chay KO

Abstract

A cytosolic protein stimulating the inactivation of glutamine synthetase (GS) by metal-catalyzed oxidation (MCO) systems was purified and characterized from the rat lung. The protein was purified through the following procedures: ammonium sulfate fractionation (40-50 %), hydroxyapatite chro- matography, HPLC reverse phase chromatography, HPLC anion exchange chromatography and Sephadex G-200 gel filtration. The purified protein was found to be nearly homogeneous. Molecular weights of the purified protein and its subunit were estimated to be about 300 kDa and 150 kDa, respectively, by gel filtration and SDS-PAGE, which suggested that the protein is composed of two identical subunits. The molecular weight and subunit structure of the protein were similar to those reported for xanthine oxidase (XO) from other organs and species. The purified protein showed the XO activity which could be inhibited by allopurinol (50 micrometer). During purification, the MCO-stimulating activity coincided exactly with the XO activity. These results suggested that the purified protein is XO. The purified protein stimulated the GS inactivation by MCO systems (e.g. ascorbate or dithiothreitol/ Cu2+/O2) in which no xanthine or hypoxanthine was present. The above results suggest that XO is a strong prooxidant stimulating MCO activities and that it may play an important role in regulating the oxidative stress in the cytosol of mammalian tissues.

Keyword

Xanthine oxidase; Prooxidant; Metal-catalyzed oxidation; Glutamine synthetase

MeSH Terms

Allopurinol
Ammonium Sulfate
Animals
Chromatography
Chromatography, Gel
Chromatography, High Pressure Liquid
Chromatography, Reverse-Phase
Cytosol
Durapatite
Electrophoresis, Polyacrylamide Gel
Glutamate-Ammonia Ligase
Hypoxanthine
Lung
Molecular Weight
Oxidative Stress
Rats
Xanthine Oxidase*
Xanthine*
Allopurinol
Ammonium Sulfate
Durapatite
Glutamate-Ammonia Ligase
Hypoxanthine
Xanthine
Xanthine Oxidase