Evidence for Nonregulatory Trehalase Activity

An in vitro activation treatment, stimulatory to the regulatory cytoplasmic trehalase of Saccharomyces cerevisiae, had no effect on the lysosomal trehalase of Dictyostelium dis- coideum. Concentrations of cAMP that produced a 19 to 22-fold increase in trehalase activity in S. cerevisiae extracts did not stimulate trehalase activity in D. discoideum extracts, cGMP and 5'-AMP were also not effective in activating the enzyme. Dictyostelium discoideum trehalase exhibits characteristics typical of nonregulatory trehalases, in agreement with its lysosomal localization. The data are consistent with the hypothesis that changes in compartmentation regulate trehalose mobilization in D. discoideum.