S -Adenosylmethionine: considerations on its role in the origin and evolution of life

in the modification of nucleobases and fatty acids but also in methionine biosynthesis. At which point of chemical and biological evolution did SAM come into play? Since SAM is closely tied to nucleotide biochemistry both structurally and biosynthetically, a discussion linking it to RNA appears to be reasonably. Apart from general overviews of the early evolutionary role of coenzymes and cofactors, the appearance of SAM on the evolutionary stage has only been dealt with superficially so far. This report attempts to achieve such a classification, both prebiotically and biosynthetically within the RNA world theory.