Abstract: The significant functions of cholesterol oxidase in food processing and medical assay for blood cholesterol level and biological pest-resistance were now gradually recognized and showed great potential in application. In this paper, we investi- gated the extraction conditions and physical properties of the membrane-bound enzyme. The 10mmol/L potassium phosphate buffer containing 0.5%Triton X-100 of pH7.5 could efficiently extract the membrane-bound enzyme from the cells with the extraction time 10 minutes. The extraction effect of sodium chloride solution with the buffer without Triton X-100 was much worse than the buffer containing Triton X-100. The enzyme assay system containing 1% Triton X-100 showed the best color of red with good stability and the highest enzyme activity. The enzyme protein contained high level of saccharide, while the proportion of saccharide and protein was 3.4:1. The optimal pH for enzyme reaction was 7.5, and the enzyme remained stable within pH5.0 to 10.0. The enzyme had kept excellent thermal stability at temperature 40℃ and even lower than 40℃.

Key words: membrane-bound cholesterol oxidase, extraction, Triton X-100, physical properties