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Membrane-associated ATPases in isolated secretory vesicles
1Department of Botany, University of Maryland, College Park, Maryland 20742.
Plant Physiology
|March 1, 1983
Summary
Secretory cell vesicles contain nucleosidephosphatases that hydrolyze ATP, suggesting partial differentiation into plasma membranes before fusion. This ATPase activity is stimulated by potassium ions.
Area of Science:
- Cell biology
- Biochemistry
- Membrane transport
Background:
- Secretory cells release polysaccharide-containing vesicles.
- The origin and differentiation state of these vesicles are not fully understood.
Purpose of the Study:
- To characterize the enzymatic activity of membrane-associated nucleosidephosphatases in vesicles from secretory cells.
- To investigate the potential role of these vesicles in plasma membrane formation.
Main Methods:
- Collection and biochemical characterization of vesicles from cultured secretory cells.
- Assay of ATPase activity, including pH optimum determination and ion stimulation studies.
- Inhibition studies using specific ATPase inhibitors.
Main Results:
- Vesicles exhibited specific ATP hydrolysis with a pH optimum of 6.0-6.5.
- ATPase activity was stimulated by inorganic cations, particularly K(+).
- Activity was inhibited by orthovanadate and N,N'-dicyclohexylcarbodiimide, but not by oligomycin or sodium azide.
Conclusions:
- The characterized nucleosidephosphatases suggest ATPase activity consistent with plasma membrane markers.
- Findings support the hypothesis that Golgi-derived vesicles undergo partial differentiation into plasmalemma prior to fusion with the plasma membrane.