Added inositol regulates invertase secretion and glucose-repressed SUC2 gene expression in Saccharomyces sp. W4.

The effect of inositol supplementation on glucose derepression, invertase secretion and SUC2 gene expression in Saccharomyces sp. W4 was studied. Invertase secretion was repressed, when the yeast cells, grown the synthetic medium without inositol (I(-) medium) contained more than 0.2% (w/v) initial concentration of glucose. However, in the same medium plus inositol (I(+) medium, inositol conc. 100 microg/100 ml), invertase secretion was repressed only at glucose concentrations higher than 2.0% (w/v). Results showed that secreted invertase activity increased only in the I+ medium, whereas intracellular invertase activity remained constant in both media during the cell, growth. The mRNA encoding secreted invertase was higher in the glucose-derepressed cells grown in the I(+) medium than in the glucose-repressed cells grown in the I(-) medium. Similarly, phosphatidylinositol (PI) content was significantly higher in the cells grown in the I(+) medium than in the I(-) medium. These results indicated that PI might be involved in the glucose derepression, invertase secretion and SUC2 gene expression at the transcriptional level in the yeast.