Modulation of trehalase activity in Saccharomyces cerevisiae by an intrinsic protein.

The regulation of cytosolic trehalase activity in yeast has been described as cycles of activation by phosphorylation by cAMP protein kinase. In this paper, evidence is presented for another regulatory mechanism--the binding of an endogenous inhibitory protein. This negative modulator was isolated during the purification procedure of cytosolic cryptic trehalase from repressed wild-type cells of Saccharomyces cerevisiae. However, in derepressed cells the inhibitor was not found nor was it present in ras2 mutant cells submitted to a heat treatment. The trehalase inhibitory activity proved to be a calmodulin ligand protein and, therefore, involved in the modulation of trehalase activity by Ca2+ ions.