Unusual intracellular accumulation of S-adenosyl-L-methionine by microorganisms.

In survey studies on microbial accumulation of S-adenosyl-L-methionine (AdoMet), various yeasts were found to accumulate AdoMet intracellularly to a high concentration when they were grown in medium containing L-methionine. A group of sake yeasts (Saccharomyces sake) exhibited especially high accumulation. Of these yeasts, S. sake Kyokai No. 6 (K-6), which exhibited the highest accumulation, produced 12.6 μmol (5.03 mg) of AdoMet/ml broth. Almost all AdoMet produced was accumulated in cells, extracellular accumulation of AdoMet being very low. The maximum content of AdoMet of cells was 5.31 μmol (205 mg)/g dry cells. This was the highest value that had been reported. Methionine adenosyltransferase (EC 2.5.1.6) activity was significantly higher in this yeast compared to those in other yeasts tested. Ultraviolet photomicrographic studies on S. sake K-6 suggested that AdoMet was gradually accumulated in vacuoles with the passage of cultivation time.