Abstract

SALVA, Terezinha J.G. et al. Some enzymatic properties of cholesterol oxidase produced by Brevibacterium sp. Rev. Microbiol. [online]. 1999, vol.30, n.4, pp. 315-323. ISSN 0001-3714.  http://dx.doi.org/10.1590/S0001-37141999000400005.

In this study we determined some properties of the cholesterol oxidase from a Brevibacterium strain isolated from buffalo's milk and identified the cholesterol degradation products by the bacterial cell. A small fraction of the enzyme synthesized by cells cultured in liquid medium for 7days was released into the medium whereas a larger fraction remained bound to the cell membrane. The extraction of this fraction was efficiently accomplished in 1 mM phosphate buffer, pH 7.0, containing 0.7% Triton X-100. The enzyme stability under freezing and at 45^oC was improved by addition of 20% glycerol. The optimum temperature and pH for the enzyme activity were 53°C and 7.5, respectively. The only steroidal product from cholesterol oxidation by the microbial cell and by the crude extract of the membrane-bound enzyme was 4-colesten-3-one. Chromatographic analysis showed that minor no steroidal compounds as well as 4-colesten-3-one found in the reaction media arose during fermentation process and were extracted together with the enzyme in the buffer solution. Cholesterol oxidation by the membrane-bound enzyme was a first order reaction type.

Keywords : Cholesterol oxidase; Brevibacterium sp; cholesterol; 3b-hydroxysteroid oxidase.