Repression of nitrogen catabolic genes by ammonia and glutamine in nitrogen-limited continuous cultures of Saccharomyces cerevisiae.

Growth of Saccharomyces cerevisiae on ammonia and glutamine decreases the expression of many nitrogen catabolic genes to low levels. To discriminate between ammonia- and glutamine-driven repression of GAP1, PUT4, GDH1 and GLN1, a gln1-37 mutant was used. This mutant is not able to convert ammonia into glutamine.