The effect of altered glycosylation on the characteristics of lysosomal trehalase in Dictyostelium discoideum

The trehalase I of Dictyostelium discoideum exhibits characteristics of a typical lysosomal enzyme. The enzyme is glycosylated and carries a number of negatively charged components which cause it to be a very acidic protein. Strain M31, bears a recessive mutation mod A which alters the post-translational modification of several lysosomal enzymes including trehalase. A direct consequence of this mutation is a reduction of the negatively charged components on lysosomal enzymes. This reduction in negativity is observed in the altered chromatographic and electrophoretic behaviour of M31 trehalase. Trehalase I is synthesized during spore germination. Tunicamycin prevents the formation of recoverable trehalase from germinating spores but does not interfere with the germination process. These results indicate that the trehalase I synthesized during spore germination is not required for the successful completion of spore germination. Minor modification in the glycosylation, as seen in strain M31, does not affect the enzymatic activity. However, when glycosylation is greatly reduced by tunicamycin the enzyme is inactive.