Enzyme repression in the arginine pathway ofSaccharomyces cerevisiae

Enzyme repression in the arginine pathway ofSaccharomyces cerevisiae was demonstrated by comparison of specific enzyme activities in yeast grown with and without arginine in various mineral salts media. Of the enzymes tested only ornithine transcarbamoylase was found to be repressed by exogenous arginine. Acetylornithine-glutamate transacetylase and argininosuccinate lyase were not affected. No relationship between specific enzyme activities and intracellular arginine concentration was observed.During the adaptation of yeast grown in a medium supplemented with amino acids to a mineral salts medium, the enzymes ornithine transcarbamoylase and argininosuccinate lyase were not derepressed beyond their specific activities normally present in yeast grown in mineral salts media. Neither were the arginine-degrading enzymes arginase and ornithine transaminase broken down during this adaptation.Thanks are due to Professor E. G. Mulder and to Professor H. Veldkamp for stimulatory discussions; to the Heineken's Brouwerij, Rotterdam, and to the Landbouwhogeschoolfonds for research grants.