Expression of streptomycete cholesterol oxidase in Escherichia coli

A streptomycete gene coding for extracellular cholesterol oxidase (choA) was subcloned and expressed in Escherichia coli. The pUCO series recombinants were obtained by inserting the choA gene into the unique KpnI site of pUC19 vector. Expression was observed with pUCO192A and pUCO193 constructs in which the cloned gene(s) were aligned with the upstream lacZ promoter. Isopropyl beta-D-thioglucopyranoside (IPTG) enhanced this expression up to 2.5-fold. Specific Cho activity in the cell extracts of the stable pUCO193 transformant were 0.004 U and 0.007 U per mg protein without and with IPTG induction, respectively. Cho activity was detected in the spent medium of this culture, suggesting possible secretion of the enzyme.