Cellular localization of neuraminidases in cultured human fibroblasts

The cellular localization of glycoprotein and ganglioside sialidases in normal and I-cell-disease cultured fibroblasts has been investigated. Cellular organelles have been separated on a colloidal silica gradient. The subcellular distribution of these enzymes indicated that the glycoprotein sialidase is mainly a lysosomal hydrolase, whereas the ganglioside sialidase is primarily located in the plasma membranes. The latter isoenzymes is tightly bound to these membranes and thus could not be extracted by homogenization in the presence of Triton X-100. The interpretation of this finding and its relation to the pathochemistry of sialidase-deficient disorders is discussed.