Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA.
Department of Chemistry, Ripon College, Ripon, WI 54971, USA.
Chembiochem. 2022 Jan 19;23(2):e202100577. doi: 10.1002/cbic.202100577. Epub 2021 Nov 15.
Enzymes from secondary metabolic pathways possess broad potential for the selective synthesis of complex bioactive molecules. However, the practical application of these enzymes for organic synthesis is dependent on the development of efficient, economical, operationally simple, and well-characterized systems for preparative scale reactions. We sought to bridge this knowledge gap for the selective biocatalytic synthesis of β-hydroxy-α-amino acids, which are important synthetic building blocks. To achieve this goal, we demonstrated the ability of ObiH, an l-threonine transaldolase, to achieve selective milligram-scale synthesis of a diverse array of non-standard amino acids (nsAAs) using a scalable whole cell platform. We show how the initial selectivity of the catalyst is high and how the diastereomeric ratio of products decreases at high conversion due to product re-entry into the catalytic cycle. ObiH-catalyzed reactions with a variety of aromatic, aliphatic and heterocyclic aldehydes selectively generated a panel of β-hydroxy-α-amino acids possessing broad functional-group diversity. Furthermore, we demonstrated that ObiH-generated β-hydroxy-α-amino acids could be modified through additional transformations to access important motifs, such as β-chloro-α-amino acids and substituted α-keto acids.
次生代谢途径中的酶具有选择性合成复杂生物活性分子的广泛潜力。然而，这些酶在有机合成中的实际应用取决于高效、经济、操作简单且经过充分表征的制备规模反应系统的开发。我们旨在为β-羟基-α-氨基酸的选择性生物催化合成填补这一知识空白，这些氨基酸是重要的合成构建块。为了实现这一目标，我们展示了 ObiH（l-苏氨酸转醛酶）的能力，该酶能够使用可扩展的全细胞平台实现各种非标准氨基酸（nsAAs）的选择性毫克级合成。我们展示了催化剂的初始选择性如何高，以及由于产物重新进入催化循环，产物的非对映体比例如何在高转化率下降低。ObiH 催化的各种芳香族、脂肪族和杂环醛的反应选择性地生成了一系列具有广泛官能团多样性的β-羟基-α-氨基酸。此外，我们证明，ObiH 生成的β-羟基-α-氨基酸可以通过进一步的转化来修饰，以获得重要的结构单元，如β-氯-α-氨基酸和取代的α-酮酸。
