Purification of xanthine oxidase from bovine milk by affinity chromatography with a novel gel
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A new affinity gel was synthesized for the purification of xanthine oxidase (XO, EC 22.214.171.124) from bovine milk. The gel was prepared on a Sepharose 4B matrix on which a spacer arm based on L-tyrosine was covalently attached via CNBr activation, followed by reaction with the XO inhibitor p-aminobenzamidine. The elution conditions of affinity gel were determined at different pH values and ionic strengths. Maximum elution of XO was achieved at pH 9.0 and ionic strength around 0.4. The overall purification for XO was 1645-fold with 20.49% yield. SDS-PAGE of the enzyme indicates a single band with an apparent MW of 150 kDa. The gel provides a simple, rapid and effective useful for the purification of XO. Heat stability was determined on purified XO activity. Xanthine oxidase was preserved up to 70% with activity exposure of 60 degrees C and incubated for 60 min. These results indicated that the enzyme was heat stable.