Induction of repressible acid phosphatase by unsaturated fatty acid in Saccharomyces cerevisiae

We studied the induction of acid phosphatase (APase) by fatty acids in Saccharomyces cerevisiae. S. cerevisiae has two types of APase: constitutive and repressible enzymes. The synthesis of the latter APase is normally derepressed by depletion of inorganic phosphate (Pi) in the incubation medium. Of the saturated and unsaturated fatty acids tested, linoleic, linolenic and arachidonic acids induced the synthesis of APase even in the presence of a high concentration of Pi, whereas palmitic, stearic and oleic acids did not. De novo protein synthesis but not stimulation of secretion of the enzyme was required for the induction. Genetic analyses using plasmids carrying the genes, PHO5 and PHO3, that code for repressible APase and constitutive APase, respectively, showed that linolenic acid induced the formation of repressible APase. Linolenic acid inhibited the uptake of exogenous 32Pi and simultaneously lowered the intracellular level of Pi. These circumstances indicate that linolenic acid-induced derepression of repressible APase is primarily caused by a fall in the intracellular level of Pi. However, cells that had been preincubated in the presence of a high concentration of Pi produced APase shortly after the addition of linolenic acid. It is, therefore, suggested that, as well as a normal regulatory mechanism for derepression of repressible APase, a mechanism independent of the external level of Pi participates in the induction of repressible APase by linolenic acid.