Novel enzymology in bacterial secondary metabolic pathways

次生代谢是一个真正的宝库不寻常的酶学作为例证黄素依赖酶催化一系列惊人的氧化还原反应，从而有助于丰富的结构多样性的天然产物。然而，尽管进行了数十年的深入研究，我们仍然只能部分理解黄素辅因子的化学多功能性和反应性。我的研究项目旨在阐明海洋链霉菌中高度不寻常的抗生素灰红菌素A的黄素依赖性生物合成。与聚酮的红霉素家族的其他成员一样，灰紫红素A对临床上重要的酶HIV逆转录酶和人端粒酶表现出显著的生物活性。因此，建议将红霉素作为潜在的先导结构用于医学应用的药物工程。值得注意的是，一个剧烈的扭曲，否则平面的红霉素结构是由一个独特的螺缩酮部分，这是至关重要的生物活性。黄素依赖性酶最有可能通过高度复杂的碳骨架重排组装这些螺缩酮药效团。为了研究这种生物合成的壮举，我将采用heterologously生产的酶，完全重建的灰红素A的生物合成途径在体外，这应该允许所有的酶促反应，途径中间体，和uncharacterized灰红素类似物的鉴定。在其功能分配之后，将对关键酶进行机械和结构表征。这种前所未有的氧化还原化学的深入了解，然后可以使生物工程的生物合成途径，以开发具有改进的药理学功能的灰红素类似物。我预计，我的研究将对扩大我们对化学反应性在自然界中如何控制的机械理解产生深远的影响，这对合成生物学的新兴领域至关重要。由于无数的生命过程依赖于黄素辅因子的催化作用，新的黄素生物化学的发现可能最终揭示细胞生物学和生理学的各个方面。

Secondary metabolism is a true treasure trove for unusual enzymology as exemplified by flavin-dependent enzymes that catalyze a wide array of astonishing redox reactions and thereby contribute to the rich structural diversity of natural products. Yet, despite decades of intensive studies, we only partially comprehend the chemical versatility and reactivity of the flavin cofactor. My research program aims to elucidate the flavin-dependent biosynthesis of the highly unusual antibiotic griseorhodin A from marine Streptomyces bacteria. Like other members of the rubromycin family of polyketides, griseorhodin A exhibits significant bioactivity against the clinically important enzymes HIV reverse transcriptase and human telomerase. Rubromycins were consequently suggested as potential lead structures for the engineering of drugs for medical application. Notably, a drastic distortion of the otherwise planar rubromycin structure is caused by a unique spiroketal moiety that is crucial for the bioactivity. Flavin-dependent enzymes most likely assemble these spiroketal pharmacophores through highly complex rearrangements of the carbon backbone. To investigate this biosynthetic feat, I will employ heterologously produced enzymes to fully reconstitute the griseorhodin A biosynthetic pathway in vitro, which should allow for the identification of all enzymatic reactions, pathway intermediates, and uncharacterized griseorhodin analogues. Subsequent to their functional assignment, the key enzymes will be mechanistically and structurally characterized. An in-depth knowledge of this unprecedented redox-chemistry may then enable the bioengineering of the biosynthetic pathway in order to develop griseorhodin analogues with improved pharmacological features. I anticipate that my studies will have a profound impact on extending our mechanistic understanding of how chemical reactivity is controlled in nature, knowledge that is paramount to the emerging field of synthetic biology. As countless life processes depend on flavin cofactor catalysis, discovery of novel flavin biochemistry may ultimately shed light into various aspects of cell biology and physiology.