Enzymes play an increasingly important role in improving the benignity and efficiency of chemical production, yet the diversity of their applications lags heavily behind chemical catalysts as a result of the relatively narrow range of reaction mechanisms of enzymes. The creation of enzymes containing non-biological functionalities facilitates reaction mechanisms outside nature’s canon and paves the way towards fully programmable biocatalysis^1,2,3. Here we present a completely genetically encoded boronic-acid-containing designer enzyme with organocatalytic reactivity not achievable with natural or engineered biocatalysts^4,5. This boron enzyme catalyses the kinetic resolution of hydroxyketones by oxime formation, in which crucial interactions with the protein scaffold assist in the catalysis. A directed evolution campaign led to a variant with natural-enzyme-like enantioselectivities for several different substrates. The unique activation mode of the boron enzyme was confirmed using X-ray crystallography, high-resolution mass spectrometry (HRMS) and ¹¹B NMR spectroscopy. Our study demonstrates that genetic-code expansion can be used to create evolvable enantioselective enzymes that rely on xenobiotic catalytic moieties such as boronic acids and access reaction mechanisms not reachable through catalytic promiscuity of natural or engineered enzymes.

酶在提高化工生产的良性和效率方面发挥着越来越重要的作用，但由于酶的反应机理相对狭窄，其应用的多样性远远落后于化学催化剂。含有非生物功能的酶的产生促进了自然规范之外的反应机制，并为完全可编程的生物催化铺平了道路^1,2,3。在这里，我们提出了一种完全基因编码的含硼酸设计酶，其具有天然或工程生物催化剂无法实现的有机催化反应性^4,5。这种硼酶通过形成肟来催化羟基酮的动力学拆分，其中与蛋白质支架的关键相互作用有助于催化。定向进化运动产生了一种对几种不同底物具有类似天然酶对映选择性的变体。使用 X 射线晶体学、高分辨率质谱 (HRMS) 和¹¹ B NMR 光谱证实了硼酶的独特激活模式。我们的研究表明，遗传密码扩展可用于创建可进化的对映选择性酶，这些酶依赖于硼酸等异生素催化部分，并获得通过天然或工程酶的催化混杂无法达到的反应机制。