A key cytochrome P450 hydroxylase in pradimicin biosynthesis
Pradimicins A–C (1–3) are a group of antifungal and antiviral polyketides from Actinomadura hibisca. The sugar moieties in pradimicins are required for their biological activities. Consequently, the 5-OH that is used for glycosylation plays a critical role in pradimicin biosynthesis. A cytochrome P450 monooxygenase gene,pdmJ, was amplified from the genomic DNA of A. hibisca and expressed in Escherichia coli BL21(DE3). PdmJ introduced a hydroxyl group to G-2A (4), a key pradimicin biosynthetic intermediate, at C-5 to form JX134 (5). A d-Ala-containing pradimicin analog, JX137a (6) was tested as an alternative substrate, but no product was detected by LC–MS, indicating that PdmJ has strict substrate specificity. Kinetic studies revealed a typical substrate inhibition of PdmJ activity. The optimal substrate concentration for the highest velocity is 115 μM under the test conditions. Moreover, the conversion rate of 4 to 5 was reduced by the presence of 6, likely due to competitive inhibition. Coexpression of PdmJ and a glucose 1-dehydrogenase inE. coli BL21(DE3) provides an efficient method to produce the important intermediate 5 from 4.
Napan, K.L., J. Zeng, J.Y. Takemoto and J. Zhan
Bioorganic & Medicinal Chemistry Letters
Napan, K.L., J. Zeng, J.Y. Takemoto and J. Zhan. 2012. A key cytochrome P450 hydroxylase in pradimicin biosynthesis. Bioorg. Med. Chem. Lett. 22: 606-609, doi:10.1016/j.bmcl.2011.10.075