Directed Evolution of Halogenases for Small Molecule Functionalization

 描述（由申请人提供）：卤代有机化合物广泛用作制药和农业化学应用的结构单元、合成中间体和最终用途产品。这些化合物的效用，包括它们的生物活性，来自于卤素取代所赋予它们的独特的反应性和物理性质。卤化的重要性和与当前卤化方法相关的局限性促使我们开发新的卤化催化剂。该建议概述了黄素依赖性卤化酶（FDH）的发展，包括选择性卤化的一系列合成方法。我们的初步结果包括通过迭代诱变的FDH定向进化的第一个例子，我们将使用我们已经开发的方法来进一步提高这些酶的底物范围，选择性和反应性，以用于实际的合成应用。这将需要产生FDH变体并筛选那些变体对相对于天然底物色氨酸具有逐渐增加的大小、改变的形状和降低的亲核性的底物的活性。然后将使用结构、动力学和计算方法来提供工程化酶的严格表征。这些数据将为后续的工程工作提供信息。具体而言，FDH将被设计为使用分子识别来覆盖底物反应性，并通过后期卤化和串联卤化/交叉偶联来调节含芳烃和烯烃的底物的生物活性。PET探针的合成使用FDH催化掺入这些化合物的正电子发射卤素也将被证明。总之，这些实验将大大推进现代合成卤化方法，并提高我们为其他C-H键官能化反应设计酶的能力。

 DESCRIPTION (provided by applicant): Halogenated organic compounds are used extensively as building blocks, synthetic intermediates, and end use products for pharmaceutical and agrochemical applications. The utility of these compounds, including their biological activity, arises from the reactivity and physical properties uniquely conferred to them by halogen substitution. The importance of halogenation and limitations associated with current halogenation methods prompted us to develop new halogenation catalysts. This proposal outlines the evolution of flavin dependent halogenases (FDHs) for a range synthetic methods involving selective halogenation. Our preliminary results include the first examples of FDH directed evolution via iterative mutagenesis, and we will use the methods we have developed to further improve the substrate scope, selectivity, and reactivity of these enzymes for practical synthetic applications. This will entail generating FDH variants and screening those variants for activity on substrates with progressively increased sizes, altered shapes, and reduced nucleophilicities, relative to the native substrate, tryptophan. Structural, kinetic, and computational methods will then be used to provide rigorous characterization of the engineered enzymes. These data will inform subsequent engineering efforts. Specifically, FDHs will be engineered to override substrate reactivity using molecular recognition and to tune the biological activity of arene and olefin-containing substrates via late-stage halogenation and tandem halogenation/cross-coupling. Synthesis of PET probes using FDH catalyzed incorporation of positron emitting halogens into these compounds will also be demonstrated. Together, these experiments will significantly advance modern synthetic halogenation methods and improve our ability to engineer enzymes for other C-H bond functionalization reactions.