J Am Chem Soc. 2006 Sep 20;128(37):12289-98.
staurosporin and rebeccamycin aglycones are assembled by
the oxidative action of staurosporin , StaC, and RebC on
chromopyrrolic acid.
Howard-Jones AR, Walsh CT.
Department of Biological Chemistry and Molecular
Pharmacology, Harvard Medical School, Boston, Massachusetts
02115, USA.
In the biosynthesis of the antitumor indolocarbazoles
rebeccamycin and staurosporin by streptomycetes, assembly of
the aglycones involves a complex set of oxidative condensations.
Overall formation of aglycones K252c and arcyriaflavin A from
their biosynthetic precursor chromopyrrolic acid involves four-
and eight-electron oxidations, respectively. This process is
catalyzed by the remarkable enzyme staurosporin , with StaC and
RebC acting to direct the level of oxidation in the newly formed
five-membered ring. An aryl-aryl coupling reaction is integral
to this transformation as well as oxidative decarboxylation of
the dicarboxypyrrole moiety of chromopyrrolic acid. Herein we
describe the heterologous expression of staurosporin , staC,
and rebC in Escherichia coli and the activity of the
corresponding enzymes in constructing the two distinct six-ring
scaffolds. StaP is a cytochrome P450 enzyme, requiring dioxygen,
ferredoxin, flavodoxin NADP(+)-reductase, and NAD(P)H for
activity. StaP on its own converts chromopyrrolic acid into
three aglycone products, K252c, arcyriaflavin A, and
7-hydroxy-K252c; in the presence of StaC, K252c is the
predominant product, while the presence of RebC directs
formation of arcyriaflavin A. (18)O-Labeling studies indicate
that the oxygen(s) of the pyrrolinone and maleimide
functionalities of the aglycones formed are all derived from
dioxygen. This work allowed for the in vitro reconstitution of
the full biosynthetic pathway from l-tryptophan to the
staurosporin and rebeccamycin aglycones, K252c and
1,11-dichloroarcyriaflavin A.
PMID: 16967980 |
