Higher Homologs and Derivatives of SAM

In 1975, Schlenk and Dainko [41] showed that, if yeast was fed with S-n-propylhomocysteine, an n-propyl analog of SAM could be detected. S-Adenosyl-r-ethionine was biosynthesized earlier [42], 

Expectedly, the reactivity in alkylation decreases dramatically with increasing carbon chain size (methyl ethyl propyl) [41]. However, double activation not only rescued but even increased the reactivity because of conjugative stabilization of the Sj 2-type transition state in vicinity of a double or triple bond [16, 43a, 45]. 

Meanwhile, an impressive number of further double activated SAM analogs bearing additional functional groups, such as -NH2, -Nj, and so on, have been 

A propynyl moiety instead of methyl also has been transferred to tRNA and pre-mRNA catalyzed by RNA 2 -0-MTase from Pyrococcus abyssi, a thermophilic archaeon, using a synthetic cofactor [55]. Terminal aUcyne groups can be subjected to click reaction in order to introduce chromophores or affinity tags. 

SAM and related cofactors, isolated or produced by total synthesis, are highly priced and their stoichiometric consumption requires one or even more equivalents. An economically feasible cofactor-dependent biocatalysis thus rehes on the substoichiometric or even catalytic use of the cofactor associated with a cofactor regeneration system, ideally in a cascaded reaction sequence. Such enzymatic conversions are assisted by an additional recycling reaction which restores the 

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