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KMID : 1134820080370111507
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Journal of the Korean Society of Food Science and Nutrition
2008 Volume.37 No. 11 p.1507 ~ p.1514
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Characterization of Extracellular Cholesterol Oxidase Produced from Soil Microorganism
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Park Jeong-Su
Jeong Jong-Moon
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Abstract
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Cholesterol oxidase catalyses the conversion of cholesterol to 4-cholesten-3-one. This enzyme has been used for clinical assay of human serum cholesterol and for reduction of cholesterol level in foods and feeds. In order to search the microorganism which has a high extracellular and stable activity of cholesterol oxidase, soil microorganisms were screened. As a result, the one with the highest extracellular cholesterol oxidase activity was obtained and named as the BEN 115. The BEN 115 strain was identified as one of the Nocardia species based on our taxonomic studies. The cholesterol oxidase from this strain was shown to have two bands of extracellular proteins on SDS-PAGE and Western blot. Their molecular masses were estimated to be about 55 and 57 kDa, respectively. In addition, this cholesterol oxidase was considerably stable at the broad range of pH 3.5～9.5 and at the temperature of 25~55℃. The optimum pH and temperature of this cholesterol oxidase were pH 5.5 and 35℃, respectively. The activity of extracellular cholesterol oxidase could be enhanced 1.6 to 2.0 folds by the addition of nonionic detergent such as Triton X-114, Triton X-100, or Tween-80 into the culturing broth. The substrate specificities against campesterol, sitosterol and stigmasterol were measured to be 50%, 50%, and 27%, respectively, compared to the cholesterol. These results suggest that Nocardia sp. BEN 115 may be useful as a microbial source of cholesterol oxidase production.
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KEYWORD
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cholesterol oxidase, cholesterol, 4-cholesten-3-one, campesterol, sitosterol, stigmasterol
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