REGULATION OF THE YEAST VACUOLAR AMINOPEPTIDASE-Y GENE (APY1) EXPRESSION

The steady-state levels of the aminopeptidase Y (APY1) transcript and the levels of assayable aminopeptidase Y activity were measured under a variety of nutritional conditions. Specific APY1 mRNA is less abunda nt in cells grown in minimal medium than in cells grown in rich medium , while active enzyme levels follow just the opposite pattern. Aminope ptidase Y activity decreases when cells are deprived of glucose withou t a concomitant fall in mRNA levels. Production of aminopeptidase Y is not markedly affected by nitrogen regulation. APY1 gene expression is not disturbed in heat-shocked cells. Our data support the idea that t he main control event in vacuolar aminopeptidase Y expression is a pos t-transcriptional step.