Characterization of TnmH as anO-Methyltransferase Revealing Insights into Tiancimycin Biosynthesis and Enabling a Biocatalytic Strategy To Prepare Antibody-Tiancimycin Conjugates.
Adhikari, A., Teijaro, C.N., Yan, X., Chang, C.Y., Gui, C., Liu, Y.C., Crnovcic, I., Yang, D., Annaval, T., Rader, C., Shen, B.(2020) J Med Chem 63: 8432-8441
- PubMed: 32658465 
- DOI: https://doi.org/10.1021/acs.jmedchem.0c00799
- Primary Citation of Related Structures:  
6CLW, 6CLX - PubMed Abstract: 
The enediynes are among the most cytotoxic molecules known, and their use as anticancer drugs has been successfully demonstrated by targeted delivery. Clinical advancement of the anthraquinone-fused enediynes has been hindered by their low titers and lack of functional groups to enable the preparation of antibody-drug conjugates (ADCs). Here we report biochemical and structural characterization of TnmH from the tiancimycin (TNM) biosynthetic pathway, revealing that (i) TnmH catalyzes regiospecific methylation at the C-7 hydroxyl group, (ii) TnmH exhibits broad substrate promiscuity toward hydroxyanthraquinones and S-alkylated SAM analogues and catalyzes efficient installation of reactive alkyl handles, (iii) the X-ray crystal structure of TnmH provides the molecular basis to account for its broad substrate promiscuity, and (iv) TnmH as a biocatalyst enables the development of novel conjugation strategies to prepare antibody-TNM conjugates. These findings should greatly facilitate the construction and evaluation of antibody-TNM conjugates as next-generation ADCs for targeted chemotherapy.