An important role for glutathione and gamma-glutamyltranspeptidase in the supply of growth requirements during nitrogen starvation of the yeast Saccharomyces cerevisiae

When the yeast Saccharomyces cerevisiae Sigma 1278b was starved for nitrogen, the total glutathione (GSH) pool increased from 7 to 17 nmol (mg dry wt)(-1) during the first 2 h and then declined. More than 90% of the total GSH shifted towards the central vacuole during this time. This transient stimulation was not observed in the presence of buthionine-(S,R)-sulphoximine (BSO), a specific transition-state-analogue inhibitor of gamma-glutamylcysteine synthase (gamma-GCS), nor in a mutant strain deficient in this enzyme. gamma-Glutamyltranspeptidase (gamma-GT), a vacuolar enzyme responsible for the initial step of GSH degradation, was derepressed during nitrogen starvation. This mechanism can apparently enable the starved yeast cell to use the constituent amino acids from GSH which accumulate in the vacuole to satisfy its growth requirements for nitrogen.