Presence of a nonlysosomal endo-beta-N-acetylglucosaminidase in the cellular slime mold Dictyostelium discoideum

Abstract

Vegetative cells of the cellular slime mold Dictyostelium discoideum have been found to contain an endo-beta-N-acetylglucosaminidase (EC 3.2.1.96) activity which hydrolyzes the di-N-acetylchitobiosyl linkage found in asparagine-linked oligosaccharides. In contrast to other previously characterized glycosyl hydrolases of Dictyostelium, this endoglycosidase is not secreted during vegetative growth or development nor is it developmentally regulated. Cellular fractionation studies showed that the endoglycosidase activity is not associated with lysosomes and remains soluble after centrifugation at 180,000g for 1 h. The enzyme has been partially purified (350-fold) from cell lysates, and its substrate specificity has been examined by its ability to hydrolyze several glycopeptides prepared from ovalbumin and from slime mold lysosomal enzymes. These preliminary studies revealed that the enzyme, called endoglycosidase S, has a substrate specificity similar to that of endo-beta-N-acetylglucosaminidase CII secreted by Clostridium perfringens.