Download MendeleyStructural basis of the mechanism of beta-methyl epimerization by enzyme MarH.
Liu, B., Hou, Y., Wang, X., Ma, X., Fang, S., Huang, T., Chen, Y., Bai, Z., Lin, S., Zhang, R., Hu, K.(2019) Org Biomol Chem 17: 9605-9614
- PubMed: 31681917
- DOI: https://doi.org/10.1039/c9ob01996k
- Primary Citation of Related Structures:
6J4B, 6J4C - PubMed Abstract:
Diverse derivatives of amino acids with different steric configurations are important biosynthetic building blocks. In biology, epimerization is an important way to generate steric diversity. MarH catalyzes the epimerization of the β-position of (3R)-β-methyl-indolepyruvate (MeInPy), forming (3S)-β-MeInPy. Both compounds are derivatives of l-tryptophan (l-Trp) and are important precursors of bioactive natural products. Here, we report the crystal structures of MarH and the NMR structure of its complex with l-Trp, an analogue of its native substrate, (3R)-β-MeInPy. Structural analysis and mutagenesis studies indicated that His25 acts as a base to remove H β and generate a planar carbanion intermediate, which is then putatively reprotonated on the opposite face by a water molecule to form (3S)-β-MeInPy in a stereospecific manner. The details of β-site isomerization at the atomic level provide deeper insights into the epimerization mechanism of MarH and will facilitate further enzyme design to extend the substrate scope.
Organizational Affiliation:
Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan 650201, China. kaifenghu@mail.kib.ac.cn and University of Chinese Academy of Sciences, Beijing, 100049, China.
