The recombinant plasmids pAMCl and pJMCl were constructed; the former contained the cytochrome P-450
MC
(P-450
MC
) cDNA expression unit consisting of yeast alcohol dehydrogenase I (ADH) promoter, rat P-450
MC
cDNA and ADH terminator, and the Leu 2 marker gene, and the latter contained the same expression unit and the leu 2-d gene.
Saccharomyces cerevisiae AH
22
cells transformed with each of the recombinant plasmids were examined for plasmid copy number, P-450
MC
mRNA level, P-450
MC
content, and monooxygenase activity. The
S. cerevisiae AH
22
/pJMCl cells contained about 2-fold higher levels of the plasmid, P-450
MC
mRNA, and P-450
MC
than the AH
22
/pAMCl cells. Monooxygenase activity towards 7-ethoxycoumarin and acetanilide of the AH
22
/pJMCl cells was 1.7-fold and 1.5-fold higher than that of the AH
22
/pAMCl cells, respectively, whereas the activity of the AH
22
/pAMCl cells towards 7-ethoxycoumarin and acetanilide was more than 1, 000-fold and 10-fold higher than that of the control AH
22
/pAAH5 ells which contain no P-450
MC
cDNA, respectively. Therefore, it is likely that monooxygenase activity of the AH
22
cells carrying rat P-450
MC
cDNA was ap-proximately proportional to the expression level of P-450
MC
cDNA.
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