Department of Molecular Enzymology, Göttingen Center of Molecular Biosciences, University of Göttingen, Göttingen, Germany.
Department of Structural Dynamics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
Nat Chem Biol. 2020 Nov;16(11):1237-1245. doi: 10.1038/s41589-020-0628-4. Epub 2020 Aug 24.
The natural antivitamin 2'-methoxy-thiamine (MTh) is implicated in the suppression of microbial growth. However, its mode of action and enzyme-selective inhibition mechanism have remained elusive. Intriguingly, MTh inhibits some thiamine diphosphate (ThDP) enzymes, while being coenzymatically active in others. Here we report the strong inhibition of Escherichia coli transketolase activity by MTh and unravel its mode of action and the structural basis thereof. The unique 2'-methoxy group of MTh diphosphate (MThDP) clashes with a canonical glutamate required for cofactor activation in ThDP-dependent enzymes. This glutamate is forced into a stable, anticatalytic low-barrier hydrogen bond with a neighboring glutamate, disrupting cofactor activation. Molecular dynamics simulations of transketolases and other ThDP enzymes identify active-site flexibility and the topology of the cofactor-binding locale as key determinants for enzyme-selective inhibition. Human enzymes either retain enzymatic activity with MThDP or preferentially bind authentic ThDP over MThDP, while core bacterial metabolic enzymes are inhibited, demonstrating therapeutic potential.
天然抗维生素 2'-甲氧基硫胺素（MTh）被认为能抑制微生物生长。然而，其作用模式和酶选择性抑制机制仍不清楚。有趣的是，MTh 抑制了一些硫胺素二磷酸（ThDP）酶，而在其他酶中则具有辅酶活性。在这里，我们报告了 MTh 对大肠杆菌转酮醇酶活性的强烈抑制作用，并揭示了其作用模式及其结构基础。MTh 二磷酸（MThDP）的独特 2'-甲氧基基团与经典的谷氨酸发生冲突，该谷氨酸对于 ThDP 依赖性酶中的辅因子激活是必需的。这种谷氨酸被迫与邻近的谷氨酸形成稳定的、反催化的低势垒氢键，从而破坏辅因子的激活。转酮醇酶和其他 ThDP 酶的分子动力学模拟确定了活性位点的灵活性和辅因子结合位置的拓扑结构是酶选择性抑制的关键决定因素。人酶要么保留与 MThDP 的酶活性，要么优先结合真实的 ThDP 而不是 MThDP，而核心细菌代谢酶则被抑制，这证明了其具有治疗潜力。
