Single-step replacement of an unreactive C-H bond by a C-S bond using polysulfide as the direct sulfur source in anaerobic ergothioneine biosynthesis
Files
Accepted manuscript
Date
2020-08-21
Authors
Cheng, Ronghai
Wu, Lian
Lai, Rui
Peng, Chao
Naowarojna, Nathchar
Hu, Weiyao
Li, Xinhao
Whelan, Stephen A.
Lee, Norman
Lopez, Juan
Version
Accepted manuscript
OA Version
Citation
R. Cheng, L. Wu, R. Lai, C. Peng, N. Naowarojna, W. Hu, X. Li, S.A. Whelan, N. Lee, J. Lopez, C. Zhao, Y. Yong, J. Xue, X. Jiang, M.W. Grinstaff, Z. Deng, J. Chen, Q. Cui, J. Zhou, P. Liu. 2020. "Single-step Replacement of an Unreactive C-H Bond by a C-S Bond Using Polysulfide as the Direct Sulfur Source in Anaerobic Ergothioneine Biosynthesis.." ACS Catal, Volume 10, Issue 16, pp. 8981 - 8994. https://doi.org/10.1021/acscatal.0c01809
Abstract
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 sp2 C-H bond in trimethyl-histidine (hercynine) through oxidation reactions. In contrast, in the anaerobic ergothioneine biosynthetic pathway in a green sulfur bacterium, Chlorobium limicola, a rhodanese domain containing protein (EanB) directly replaces this unreactive hercynine C-H bond with a C-S bond. Herein, we demonstrate that polysulfide (HSSnSR) 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 Nπ of hercynine by Tyr353 with the assistance of Thr414 is a key activation step for the hercynine sp2 C-H bond in this trans-sulfuration reaction.