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Journal of Bacteriology, January 1999, p. 298-304, Vol. 181, No. 1
Department of
Microbiology1 and
College of
Pharmacy,2 Ohio State University, Columbus, Ohio
43210
Received 27 July 1998/Accepted 16 October 1998
DoxA is a cytochrome P-450 monooxygenase involved in the late
stages of daunorubicin and doxorubicin biosynthesis that has a broad
substrate specificity for anthracycline glycone substrates. Recombinant
DoxA was purified to homogeneity from Streptomyces lividans
transformed with a plasmid containing the Streptomyces sp.
strain C5 doxA gene under the control of the strong
SnpR-activated snpA promoter. The purified enzyme was a
monomeric, soluble protein with an apparent Mr
of 47,000. Purified DoxA catalyzed the 13-hydroxylation of
13-deoxydaunorubicin, the 13-oxidation of 13-dihydrocarminomycin and
13-dihydrodaunorubicin, and the 14-hydroxylation of daunorubicin. The
pH optimum for heme activation was pH 7.5, and the temperature optimum
was 30°C. The kcat/Km
values for the oxidation of anthracycline substrates by purified DoxA,
incubated with appropriate electron-donating components, were as
follows: for 13-deoxydaunorubicin, 22,000 M
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Purification, Properties, and Characterization of
Recombinant Streptomyces sp. Strain C5 DoxA, a Cytochrome
P-450 Catalyzing Multiple Steps in Doxorubicin Biosynthesis

1 · s
1; for 13-dihydrodaunorubicin, 14,000 M
1 · s
1; for 13-dihydrocarminomycin,
280 M
1 · s
1; and for daunorubicin,
130 M
1 · s
1. Our results indicate
that the conversion of daunorubicin to doxorubicin by this enzyme is
not a favored reaction and that the main anthracycline flux through the
late steps of the daunorubicin biosynthetic pathway catalyzed by DoxA
is likely directed through the 4-O-methyl series of anthracyclines.
*
Corresponding author. Present address: Merck Research
Laboratories, P.O. Box 2000, R80Y-215, Rahway, NJ 07065. Phone: (732) 594-8433. Fax: (732) 594-1399. E-mail:
william_strohl{at}merck.com.
Present address: Merck Research Laboratories, P.O. Box 2000, RY810, Rahway, NJ 07065.
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