Nonenzymatic oxidative steps accompanying action of the cytochrome p450 enzymes StaP and RebP in the biosynthesis of staurosporine and rebeccamycin
Nonenzymatic oxidative steps accompanying action of the cytochrome p450 enzymes StaP and RebP in the biosynthesis of staurosporine and rebeccamycin
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DOI：
10.1021/ja0743801
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发表时间：
2007-09-12
影响因子：
15
通讯作者：
Walsh, Christopher T.
中科院分区：
文献类型：
--
作者：
Howard-Jones, Annaleise R.;Walsh, Christopher T.
在吲哚并咔唑天然产物星形孢菌素和瑞贝卡霉素的生物合成中，一组复杂的氧化转化导致一对L-色氨酸单体的二聚化和氧化交联。参与这一途径的氧化酶中最有趣的是StaP（或其同系物RebP），它似乎催化色吡咯酸的4 - 8电子氧化，得到一组三个糖苷配基，在吡咯衍生环中氧化态不同。在这项工作中，我们试图澄清StaP在这一过程中的催化作用，并深入了解其产品特征明显缺乏特异性。通过一个假定的中间体的制备，我们表明，所有的步骤下游的芳基-芳基耦合可以发生非酶在溶液中，精确定位的功能StaP作为一个两电子的芳基-芳基耦合催化剂，作用于chromopyrrolic酸。因此，StaP加入了一个小但不断增长的芳基-芳基偶联酶家族，该家族使用基于P450的化学物质来促进这种氧化转化。此外，使用环氘代基板，我们表明，这种芳基-芳基耦合过程是不是一个限速步骤，在整体形成的糖苷配基。这项工作扩展了我们以前的研究，涉及的生物合成酶的星形孢菌素和rebeccamycin途径和行为，以阐明具体的作用，StaP和RebP在这些生物合成的背景下。
In the biosynthesis of the indolocarbazole natural products staurosporine and rebeccamycin, a complex set of oxidative transformations results in dimerization and oxidative cross-linking of a pair of L-tryptophan monomers. Most intriguing among the oxidative enzymes involved in this pathway is StaP (or its homologue, RebP), which appears to catalyze the four- to eight-electron oxidation of chromopyrrolic acid to give a set of three aglycones, differing in oxidation state in the pyrrole-derived ring. In this work, we sought to clarify the catalytic role of StaP in this process and gain insight into the apparent lack of specificity in its product profile. Through the preparation of a putative intermediate, we show that all steps downstream of aryl-aryl coupling can occur nonenzymatically in solution, pinpointing the function of StaP as a two-electron aryl-aryl coupling catalyst that acts on chromopyrrolic acid. StaP thus joins a small but growing family of aryl-aryl coupling enzymes that use P450-based chemistry to facilitate this oxidative transformation. Furthermore, using ring-deuterated substrate, we show that this aryl-aryl coupling process is not a rate-limiting step in the overall formation of the aglycones. This work expands on our previous studies on the biosynthetic enzymes involved in the staurosporine and rebeccamycin pathways and acts to illuminate the specific roles of StaP and RebP in the context of these biosyntheses.