催化学报 ›› 2027, Vol. 92: 442-451.DOI: 10.1016/S1872-2067(26)65279-5

• 论文 • 上一篇    

工程化改造亚胺还原酶实现4-取代环己酮的立体发散还原胺化

赵顺宇a,b,c, 张鑫平a,b,c, 顾翔源a,b,c, 周婕妤a,b,c,*(), 倪晔a,b,c,*()   

  1. a 江南大学食品科学与资源挖掘全国重点实验室, 无锡 214122
    b 江南大学生物工程学院, 工业生物技术教育部重点实验室, 无锡 214122
    c 江苏省工业合成生物学重点实验室, 无锡 214122
  • 收稿日期:2026-07-15 接受日期:2026-08-17 出版日期:2027-01-02 发布日期:2026-10-30
  • 通讯作者: *电子信箱: zhoujieyu@jiangnan.edu.cn (周婕妤),
    yni@jiangnan.edu.cn (倪晔).
  • 基金资助:
    江苏省先进技术研发计划(BF2025072);国家自然科学基金(22377040);江南大学食品科学与资源国家重点实验室研究项目(SKLF-ZZA-202503);江苏省基础研究计划和江苏省合成生物学基础研究中心(BK20233003);江苏省研究生科研与实践创新计划(KYCX25_2717)

Engineering imine reductases enables stereodivergent reductive amination of 4-substituted cyclohexanones

Shunyu Zhaoa,b,c, Xinping Zhanga,b,c, Xiangyuan Gua,b,c, Jieyu Zhoua,b,c,*(), Ye Nia,b,c,*()   

  1. a State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi 214122, Jiangsu, China
    b Key laboratory of industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, Jiangsu, China
    c Key Laboratory of Industrial Synthetic Biology of Jiangsu Province, Jiangnan University, Wuxi 214122, Jiangsu, China
  • Received:2026-07-15 Accepted:2026-08-17 Online:2027-01-02 Published:2026-10-30
  • Contact: *E-mail: zhoujieyu@jiangnan.edu.cn (J. Zhou),
    yni@jiangnan.edu.cn (Y. Ni).
  • About author:First author contact:

    S. Z., X. Z. and X. G. performed and analyzed the experiments. S. Z., J. Z. and Y. N. conceived the project and designed the experiments. S. Z., J. Z. and Y. N. wrote the manuscript. All authors have given approval to the final version of the manuscript.

  • Supported by:
    Advanced Technology Re-search and Development Program of Jiangsu Province(BF2025072);National Natural Science Foundation of China(22377040);Research Program of State Key Laboratory of Food Science and Resources, Jiangnan University(SKLF-ZZA-202503);Basic Re-search Program of Jiangsu and Jiangsu Basic Research Center for Synthetic Biology(BK20233003);Postgraduate Research & Practice Innovation Program of Jiangsu Province(KYCX25_2717)

摘要:

立体异构胺类砌块广泛存在于各种生物活性分子中, 是合成药物、天然产物、精细化学品等的重要中间体. 不同4-取代环己酮羰基的还原胺化可以得到不同的顺式/反式环己胺, 而这种具有明确立体选择性的分子砌块才是产生药物活性的关键. 相较于传统化学合成方法, 生物法不对称合成胺类化合物具有绿色、高效、高立体选择性等优势. 伴随国内外亚胺还原酶的发现与发展, 进一步开发的亚胺还原酶工具箱为立体异构胺的合成提供了更理想的途径. 然而, 其在4-取代环己胺合成中的应用仍未得到充分探索. 因此, 改造亚胺还原酶以实现4-取代环己胺的高选择性合成在生物活性分子合成领域具有重要实用价值.

本研究鉴定出一个控制亚胺还原酶催化还原胺化反应中顺式/反式选择性的单一位点立体控制残基, 并建立了适用于4-取代环己胺立体发散性合成的普适性改造策略. 通过系统发育分析指导下的亚胺还原酶同源酶筛选, 获得了一组能高效催化4-乙基环己酮与胺供体反应, 且呈现差异化非对映选择性的酶. 结合结构导向的定向进化策略对I127位点进行突变后获得了两个互补的突变体I127L和I127P. 在4-乙基环己酮与炔丙胺的还原胺化反应中, I127L可得到非对映体过量(de)高达95%的顺式产物, 而I127P则生成de高达92%的反式产物. 进一步拓展底物谱, 证实了这两个突变体均适用于多种酮类与胺类底物. 分子动力学模拟揭示, IRZ06的第127位残基通过空间位阻门控和疏水相互作用调控底物取向. 在野生型中, I127侧链的空间位阻限制了底物乙基的朝向, 同时M214/A239/H244在六元环同侧形成疏水作用促进顺式构型生成, I127P突变释放了空间位阻并建立新的烷基相互作用, 使底物以不同取向结合从而生成反式构型, I127L则通过更大体积侧链增强位阻, 促使Y221与底物形成烷基相互作用, M125烷基链与六元环平行形成疏水接触, 进一步稳定顺式构型. 此外, 对其他9种亚胺还原酶中对应于IRZ06第127位的等效残基进行了评估, 证实了该位点在亚胺还原酶非对映选择性中的关键作用. 具体而言, 第127位为脯氨酸(Pro)时偏好于反式选择性, 而亮氨酸(Leu)则有利于顺式选择性. 这说明该关键位点在调控亚胺还原酶不对称还原胺化4-取代环己酮的过程中具有普适性.

综上, 本文通过亚胺还原酶突变体实现了多种4-取代环己胺的立体发散性合成, 并揭示了一个控制亚胺还原酶非对映选择性的关键残基, 为工程化改造亚胺还原酶以获取具有特定立体化学构型的环己胺结构单元提供了一种通用策略.

关键词: 亚胺还原酶, 立体发散性还原胺化, 4-取代环己胺, 非对映选择性, 生物催化

Abstract:

Imine reductases (IREDs) enable sustainable routes to stereochemically defined amines. However, their synthetic application to 4-substituted cyclohexanones, important scaffolds in pharmaceutical chemistry, remains underexplored. Here, we identified a key residue in IREDs that acts as a stereochemical switch governing cis/trans selectivity, and established a feasible and efficient approach for stereodivergent synthesis of 4-substituted cyclohexylamines. Phylogeny-guided mining of IREDs homologues yielded a subset of ten enzymes capable of catalyzing reductive amination of 4-ethylcyclohexanone in high efficiency whereas distinct diastereoselectivity. MD simulations reveal that residue 127 of IRZ06 modulates substrate orientation through steric gating and hydrophobic interactions. Mutagenesis at I127 produced two complementary variants I127L and I127P. Using a range of ketones substrates and amine donors, I127L afforded cis-products up to 95% de, whereas I127P resulted trans-products with up to 92% de. Further assessment was conducted at equivalent position of residue 127 in IRZ06 across nine IREDs, demonstrating its essential role in diastereoselectivity. Specifically, residue Pro at 127 consistently induced trans-selectivity, and Leu favored cis-selectivity. This work reveals a key residue governing diastereoselectivity of IREDs, offering a generally applicable strategy for engineering IREDs to access stereochemically defined cyclohexylamine building blocks.

Key words: Imine reductases, Stereodivergent reductive amination, 4-Substituted cyclohexylamines, Diastereoselectivity, Biocatalysis