Multiple forms of trehalase during development in Dictyostelium discoideum

Abstract

The specific activity of intracellular trehalase decreased 5- to 10-fold during the first 14 hr of development in the cellular slime mold, Dictyostelium discoideum. During the last 10 h (i.e., culmination), enzymatic activity increased 10-fold and was maximal in mature sorocarps. Accompanying these changes in intracellular enzyme was the biphasic appearance of extracellular trehalase. Alterations in the electrophoretic profile of trehalase accompanied the changes in activities of the intra- and extracellular enzymes. Although a single intracellular trehalase activity (i.e., isozyme I) was detectable prior to 14 h, during culmination a second form of the enzyme, i.e., isozyme II, accumulated. Multiple extracellular trehalase activities were also detectable during development. Extracellular enzyme accumulated during the first 14 h (i.e., isozyme I′) had an R m value equal to that of isozyme I, while the major activity accumulated during culmination was isozyme II′, having an R m identical to that of isozyme II. Since previous studies ( B.L. Jefferson and C.L. Rutherford, 1976, Exp. Cell Res. 103: 127–134) have indicated that the increase in enzyme specific activity occurring during culmination is uniquely localized in the stalk, the results of the present study suggest that this may be due to a cell type-specific accumulation of isozyme II.