Doping In Vivo Alkylation in E. coli by Introducing the Direct Sulfurylation Pathway of S. cerevisiae

Methylation and alkylation are important techniques used for the synthesis and derivatisation of small molecules and natural products. Application of S-adenosylmethionine (SAM)-dependent methyltransferases (MTs) in biotechnological hosts such as Escherichia coli lowers the environmental impact of alkylation compared to chemical synthesis and facilitates regio- and chemoselective alkyl chain transfer. Here, we address the limiting factor for SAM synthesis, methionine supply, to accelerate in vivo methylation activity. Introduction of the direct sulfurylation pathway, consisting of O-acetylhomoserine sulfhydrolase (ScOAHS) and O-acetyltransferase (ScMET2), from S. cerevisiae into E. coli and supplementation with methanethiol or the corresponding disulfide improves atom-economic methylation activity in three different MT reactions. Up to 17-fold increase of conversion compared to the sole expression of the MT and incorporation of up to 79 % of the thiol compound added were achieved. Promiscuity of ScOAHS allowed in vivo production of methionine analogues from organic thiols. Further co-overproduction of a methionine adenosyltransferase yielded SAM analogues which were further transferred by MTs onto different substrates. For methylation of non-physiological substrates, conversion rates up to 73 % were achieved, with an isolated yield of 41 % for N-methyl-2,5-aminonitrophenol. The here described technique enables E. coli to become a biotechnological host for improved methylation and selective alkylation reactions.