Darstellung von35S-Methionin und35S-Cystin hoher spezifischer Aktivität durch Biosynthese

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Abstract
The method employs the yeast Torula utilis. The cells are first grown in a medium deficient in sulfur until there is decrease in the growth rate. They are then transferred to an S35-sulfate containing medium. The pH is kept constant by means of addition of ammonia. The cells are allowed to grow for 4-6 hours; in this way it is possible to obtain 25 mg cells containing 50 mC S35. The cells are then hydrolyzed with 5 [image] HC1 for 24 hours at 100 [degree]C and methionine is isolated by paper chromatography under N. Activities of over 100 mC/mg can be obtained. Cystine is isolated from cells which are first extracted with trichloracetic acid to remove nucleic acids and ethanol-carbon tetrachlorlde to remove lipids. The residue is then hydrolyzed with 5 [image] HC1 for 5 hours at 100[degree]C and the hydrolysate again chromatographed on paper. The isolated methionine accounts for about 40% of the S35 incorporated by the yeast, and the cystine for 20%.