Intracellular Binding and Transport of Lysosomal Enzymes in Human and Bovine Tissues
Lysosomal enzymes are glycoproteins with high mannose type oligosaccharides in their molecules. Mannose 6-phosphate has been found in these sugar chains and characterized as a specific recognition marker of these enzymes in mammalian cells. Recent studies revealed that the phosphomannosyl receptor binds and transports enzyme molecules to lysosomes (Sly and Fischer, 1982). Two types are known in this receptor, but details of its properties are not yet fully understood. The receptor is considered to be localized on the inner surface of the endoplasmic reticulum and Golgi apparatus (Brown and Fahrquhar, 1984; Fischer et al., 1980; Willingham et al., 1983). It was purified from some mammalian tissues (Brown and Fahrquhar, 1984; Fischer et al., 1982; Sahagian et al., 1981; Sahagian et al., 1982; Steiner and Rome, 1982). These studies demonstrated a single protein with the same molecular weight of 215,000 on SDS-polyacrylamide gel electrophoresis (SDS-PAGE) under reducing conditions. However, Mitchell et al. (1984) found a partial dissociation of the 215 kDa phosphomannosyl receptor from bovine liver after storage at 4°C for 6 months in the absence of mannose 6-phosphate.
KeywordsLysosomal Enzyme Intracellular Transport Bovine Liver Control Liver Acid Soluble Fraction
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