MODULATION OF TREHALASE ACTIVITY IN SACCHAROMYCES-CEREVISIAE BY AN INTRINSIC PROTEIN

The regulation of cytosolic trehalase activity in yeast has been descr ibed as cycles of activation by phosphorylation by cAMP protein kinase . In this paper, evidence is presented for another regulatory mechanis m - the binding of an endogenous inhibitory protein. This negative mod ulator was isolated during the purification procedure of cytosolic cry ptic trehalase from repressed wild-type cells of Saccharomyces cerevis iae. However, in derepressed cells the inhibitor was not found nor was it present in ras2 mutant cells submitted to a heat treatment. The tr ehalase inhibitory activity proved to be a calmodulin ligand protein a nd, therefore, involved in the modulation of trehalase activity by Ca2 + ions.