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18.3 Conclusion and Outlook 417

acids into the corresponding methyl esters [71] which are the main constituents of
biofuel. Another promising candidate is CypM, an NMT isolated from Streptomyces
sp., which might be a useful tool in the post-translational modification of the
α-amino group of peptides [104]. The most relevant preparative applications were,
and in the near future likely will be, those of OMTs. They are usually more
promiscuous than their C-and N-affine relatives, and access and application by
nonexperts is easier.
Overall, MTs have great potential for applications in biotechnology. The require-
ments for ‘‘Green Chemistry’’ and the hazardous properties of alkylating agents in
general make the substitution of existing methods and processes inevitable. MTs
can provide excellent chemo- and regioselectivity, sometimes contrasting those of
chemical methylation processes. The enzymes are well behaved in biocatalysis and
usually not very sensitive. Nevertheless, only very few applications of selected MTs
seem to be mature [28, 57a, 90], with most of the work done still in infancy. Thus
there is a huge potential for improvements and new developments, such as SAM
regeneration, its substitution by simple alkyl donors, design of more active variants,
expansion of substrate, and cofactor scope, to name just a few. This by no means
exhaustive list of future tasks for research and development in the field of MTs will
soon become shorter considering the importance of methylation processes in the
bio-based productions of high-value products and in influencing cellular processes.

Abbreviations

MT methyltransferase
NMT N-methyltransferase
OMT O-methyltransferase
SAH S-adenosyl-l-homocysteine
SAM S-adenosyl-l-methionine
Met methionine
THF tetrahydrofolate

Acknowledgement

This work has been partially supported by the Federal Ministry of Economy, Family
and Youth (BMWFJ), the Federal Ministry of Traffic, Innovation and Technology
(bmvit), the Styrian Business Promotion Agency SFG, the Standortagentur Tirol
and ZIT – Technology Agency of the City of Vienna through the COMET-
Funding Program managed by the Austrian Research Promotion Agency FFG.
MGK acknowledge financial support from the Austrian Science Foundation (FWF)
through project P24135-N17 and Innovative Medicines Initiative (IMI) project
◦
n 115360.
It was also partially supported by EU COST actions FA 1006 (PlantEngine) and FA
0907 (Bioflavour), FP7 KBBE-Project BioNexGen (no 266025, Developing the Next
Generation of Biocatalysts for Industrial Chemical Synthesis), Science Campus