A xanthine oxidase (XOD) was expressed, purified and partially characterized from Arthrobacter sp. with a negative immune protocol. To determine the optimal inducer for XOD, xanthine, hypoxanthine and uric acid were added into the medium of cultivation. The results revealed that with the inducement of about 14 mM xanthine, the highest XOD activity could be detected. To separate XOD from Arthrobacter sp., the cells were first cultured without any inducement; then the total proteins of the collected cells were extracted and immunized to rabbits for the polyclonal antibodies. These antibodies were then coupled with sepharose CL 6 B, and the medium was further employed to deplete most of the cells' back ground proteins. Began with similar to 20 mg crude protein from disrupted cells was subjected to the antibody medium, and similar to 1.45 mg protein was detected in unbinding fractions with similar to 92.0% of activity. The extracted xanthine oxidase was similar to 85% pure with native-PAGE analysis, and similar to 90% pure with SDS-PAGE analysis, the yield of protein was similar to 7.4%. The specific activity of the enzyme was 36.0 U/mg. The native enzyme should be a dimer (similar to 280 kDa) of a protein composed with two different peptides with the mass of approximately 55.5 and 85.5 kDa, respectively. The optimal pH and temperature of this enzyme were determined at about pH 7 and 50 degrees C. Furthermore, EDTA revealed almost no influences on the activity. (C) 2012 Elsevier Ltd. All rights reserved.