Subcellular forms of cholesterol oxidase from Rhodococcus sp. CIP 105 335: induction, solubilization and characterization

Cholesterol oxidase (COX) induction in cells of Rhodococcus sp. (CIP 105335, strain GK1) depended on the sterol side chain. Octanoate, or Tween 80 showed a stimulating effect on enzyme synthesis by this strain. COX occurred in a secreted form and/or a cell surface-bound form depending on the carbon source used for strain growth. Extractability of the cell surface-linked form from cells with phosphate buffer or the buffer containing non-ionic detergent varied as the carbon source varied. The detergent-extracted COX was co-solubilized with mycolate and three proteins of around 52, 26, and 19 kDa. Some of these cell surface proteins might be involved in COX fixation into mycolate-rich cell surface. The secreted, buffer-extracted, and detergent-extracted enzyme forms showed the same substrate specificity and molecular mass, around 60 KDa. COX of GK1 is exported outside of the cell membrane, and either localized onto the cell surface, or released into the growth medium depending on the carbon source.