Identification and Engineering of Novel N‐Methyltransferases

The methylation of small molecules is of immense value to various chemical industries. Since chemical alkylation requires rather unselective and harsh reaction conditions, sustainable biocatalytic approaches are highly desired. Methyltransferases, particularly N‐methyltransferases (NMTs), facilitate the selective introduction of methyl (and other alkyl) groups under mild conditions in aqueous solution and are a promising alternative to chemical synthesis. In this work, we expanded the toolbox of NMTs through the bioinformatic‐assisted mining of databases and the high‐throughput characterization of novel NMTs by a fluorescence‐based assay. The latter can assess enzyme activity in cell lysates, independent of the investigated substrate, and was used to guide the engineering of newly identified NMTs. Mutants, exhibiting up to 8‐fold improved selective methylation of (non‐)natural N‐heterocyclic drug precursors, were identified and promise great potential for synthetic applications.