TREHALASE ACTIVATION-INDUCED BY NUTRIENTS AND METABOLIC-INHIBITORS INZYGOSACCHAROMYCES-ROUXII

Cells of Zygosaccharomyces rourii suspended in buffer responded to the addition of both fermentable and nonfermentable sugars by increasing trehalase activity. This response was preceded by a cyclic-AMP (cAMP) signal. In contrast to previous findings in other yeast species, the g lucose-induced trehalase activation is not repressed by glucose in the se cells. The protonophore 2,4-dinitrophenol also triggered a transien t activation of trehalase but this response was not accompanied by an increase in cAMP. However, nitrogen sources, protein-synthesis inhibit ors and the respiratory inhibitor sodium azide did not induce activati on of trehalase. Incubation of cell extracts with ATP and cAMP produce d an in vitro activation of trehalase, suggesting that the enzyme may be stimulated in vivo by phosphorylation. The above results support th e existence in Z. rouxii of both cAMP-dependent and cAMP-independent p hosphorylation pathways which share trehalase as a molecular target. T hese activation pathways are markedly different in many respects from those induced in yeasts like Saccharomyces cerevisiae, Candida utilis, and Schizosaccharomyces pombe, suggesting a species-specific design i n the signal transduction systems involved in trehalase activation.