Division of Chemistry and Chemical Engineering 210-41, California Institute of Technology, 1200 East California Boulevard, Pasadena, California, 91125, USA.
Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, WI, 53706, USA.
Angew Chem Int Ed Engl. 2018 Nov 5;57(45):14764-14768. doi: 10.1002/anie.201807998. Epub 2018 Oct 12.
Noncanonical amino acids (ncAAs) with dual stereocenters at the α and β positions are valuable precursors to natural products and therapeutics. Despite the potential applications of such bioactive β-branched ncAAs, their availability is limited due to the inefficiency of the multistep methods used to prepare them. Herein we report a stereoselective biocatalytic synthesis of β-branched tryptophan analogues using an engineered variant of Pyrococcus furiosus tryptophan synthase (PfTrpB), PfTrpB . PfTrpB is the first biocatalyst to synthesize bulky β-branched tryptophan analogues in a single step, with demonstrated access to 27 ncAAs. The molecular basis for the efficient catalysis and broad substrate tolerance of PfTrpB was explored through X-ray crystallography and UV/Vis spectroscopy, which revealed that a combination of active-site and remote mutations increase the abundance and persistence of a key reactive intermediate. PfTrpB provides an operationally simple and environmentally benign platform for the preparation of β-branched tryptophan building blocks.
非天然手性氨基酸（ncAAs）在α和β位具有双重手性中心，是天然产物和治疗药物的有价值前体。尽管这种具有生物活性的β支链 ncAAs 具有潜在的应用，但由于制备它们的多步方法效率低下，其可用性受到限制。在此，我们报告了一种使用 Pyrococcus furiosus 色氨酸合酶（PfTrpB）的工程变体对β-支链色氨酸类似物进行立体选择性生物催化合成的方法，PfTrpB 是第一个能够在一步反应中合成大体积β-支链色氨酸类似物的生物催化剂，已经证明可以获得 27 种 ncAAs。通过 X 射线晶体学和紫外/可见光谱研究了 PfTrpB 高效催化和广泛底物耐受性的分子基础，结果表明，活性位点和远程突变的组合增加了关键反应中间体的丰度和稳定性。PfTrpB 为制备β-支链色氨酸砌块提供了一种操作简单、环境友好的平台。
