Valanimycin, an antibiotic with antitumor activity, is produced by Streptomyces viridifaciens MG456-hF10. This molecule contains an azoxy group and is being studied to learn more about the synthesis of naturally occurring azoxy compounds (Tao et al., 2003.
Valanimycin is synthesized by condensation of L-serine with isobutylhydroxylamine; the latter compound is produced from L-valine via isobutylamine. A key step in the synthesis pathway, the oxidation of isobutylamine to isobutylhydroxylamine, is catalysed by a two-component flavin monooxygenase. The two components are isobutylamine N-hydroxylase and NAD(P)H:FAD oxidoreductase. The second component is required to provide reduced flavin cofactor since isobutylamine N-hydroxylase is unable to reduce FAD or FMN on its own. Purification of isobutylamine N-hydroxylase from Streptomyces viridifaciens has been reported (Parry et al., 1997). The exact mechanism of N-N bond formation is not very clear. However, Tao et al. (2003) have proposed 2 possible mechanisms for the incorporation of L-serine.
The following is a text-format of valanimycin biosynthesis pathway map. An organism that can catalyze the last step of the synthesis is shown; other organisms may also carry out earlier steps. Follow the links for more information on compounds or reactions. This map is also available in graphic (7k) format.
Valanimycin Streptomyces viridifaciens MG456-hF10 ^ | | ^ A +-----L-Serine---------->| | | | | | Isobutylhydroxylamine | ^ | | | | isobutylamine N-hydroxylase | | | | | Isobutylamine | ^ | | | | valine decarboxylase | | | | | L-Valine | ^ | | | | | | | | | | Intermediary Intermediary Metabolism Metabolism (KEGG) (KEGG)
Page Author(s): Lynda Ellis, Yogesh Kale
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