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Abstract
SUMMARY: When exponentially growing Dictyostelium discoideum amoebae were harvested from growth medium and suspended in a nutrient-free phosphate buffer, the cells released 20 to 30% of their total β-N-acetylglucosaminidase and α-mannosidase activities. This release was inhibited by sodium azide but stimulated (to a level of 90% release) by various saccharides when added to the phosphate buffer at millimolar concentrations. Various salts, amino acids and nucleotides were unable to stimulate the release process. Non-metabolizable sugars were more stimulatory than metabolizable sugars, but no clear distinction related to structure, ability to be transported or ability to be metabolized was found to account directly for the varying effects of the sugars on glycosidase release. The rate and amount of glycosidase release was dependent on the sugar concentration but not on the cell density. The results presented suggest that sugars stimulate a specific release of a variety of lysosomal enzymes and the relationship of this release to D. discoideum morphogenesis is discussed.
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