Biosynthesis of S-adenosylmethionine in a recombinant yeast strain

The present invention makes use of a chimeric gene that, when incorporated into an appropriate host, results in the overproduction of S-adenosylmethionine without the need to supply the host with a source of untransformed methionine. The need for the methionine source is eliminated because the appropriately chosen host manufactures the amino acid on its own, and when the host is modified by the inclusion of a chimeric gene of the present invention, it transforms the methionine that is produced into S-adenosylmethionine. In addition, the same chimeric gene causes accumulation of methionine and increase in folate content in the same host. One form of the present invention is a fused gene encoding for methylene tetrahydrofolate reductase (MTHFR) made up of an N-terminal domain from a yeast organism and a C-terminal domain from a plant species. An example of a suitable plant species is Arabidopsis thaliana. An example of a suitable yeast organism is Saccharomyces cerevisiae.