Cheng Ronghai, Wu Lian, Lai Rui, Peng Chao, Naowarojna Nathchar, Hu Weiyao, Li Xinhao, Whelan Stephen A, Lee Norman, Lopez Juan, Zhao Changming, Yong Youhua, Xue Jiahui, Jiang Xuefeng, Grinstaff Mark W, Deng Zixin, Chen Jiesheng, Cui Qiang, Zhou Jiahai, Liu Pinghua
Department of Chemistry, Boston University, Boston, MA 02215, USA.
State Key Laboratory of Bio-organic and Natural Products Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Shanghai 200032, China.
ACS Catal. 2020 Aug 21;10(16):8981-8994. doi: 10.1021/acscatal.0c01809. Epub 2020 Jul 16.
Ergothioneine, a natural longevity vitamin and antioxidant, is a thiol-histidine derivative. Recently, two types of biosynthetic pathways were reported. In the aerobic ergothioneine biosynthesis, a non-heme iron enzyme incorporates a sulfoxide to an sp C-H bond in trimethyl-histidine (hercynine) through oxidation reactions. In contrast, in the anaerobic ergothioneine biosynthetic pathway in a green sulfur bacterium, , a rhodanese domain containing protein (EanB) directly replaces this unreactive hercynine C-H bond with a C-S bond. Herein, we demonstrate that polysulfide (HSSSR) is the direct sulfur-source in EanB-catalysis. After identifying EanB's substrates, X-ray crystallography of several intermediate states along with mass spectrometry results provide additional mechanistic details for this reaction. Further, quantum mechanics/molecular mechanics (QM/MM) calculations reveal that protonation of N of hercynine by Tyr353 with the assistance of Thr414 is a key activation step for the hercynine sp C-H bond in this trans-sulfuration reaction.
麦角硫因是一种天然的长寿维生素和抗氧化剂，是一种硫醇 - 组氨酸衍生物。最近，报道了两种生物合成途径。在有氧麦角硫因生物合成中，一种非血红素铁酶通过氧化反应将亚砜结合到三甲基组氨酸（肌肽）的sp C-H键上。相比之下，在绿色硫细菌的厌氧麦角硫因生物合成途径中，一种含硫代硫酸酶结构域的蛋白质（EanB）直接用C-S键取代了这种无反应性的肌肽C-H键。在此，我们证明多硫化物（HSSSR）是EanB催化反应中的直接硫源。在确定了EanB的底物后，几种中间状态的X射线晶体学以及质谱结果为该反应提供了更多的机理细节。此外，量子力学/分子力学（QM/MM）计算表明，在Thr414的协助下，Tyr353使肌肽的N质子化是该转硫反应中肌肽sp C-H键的关键活化步骤。
