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Effect of diadenosine polyphosphates on Ca2+ ATPase activity
J Jankowski1, H Schlüter, M Tepel
1Universitäts-Klinik Marienhospital, Ruhr-Universität Bochum, Herne, Germany.
Journal of Molecular Medicine (Berlin, Germany)
|November 14, 1997
Summary
Diadenosine polyphosphates, including Ap5A and Ap6A, enhance Ca2+ ATPase activity. This finding suggests a physiological role for these compounds in regulating cellular calcium levels.
Area of Science:
- Biochemistry
- Molecular Biology
- Cardiovascular Physiology
Background:
- Diadenosine polyphosphates (Ap3A-Ap6A) exhibit varied effects on vascular tone.
- The influence of these molecules on cellular enzyme activity remains an area of investigation.
Purpose of the Study:
- To investigate the impact of diadenosine tri-, tetra-, penta-, and hexaphosphate (Ap3A, Ap4A, Ap5A, Ap6A) on Ca2+ ATPase activity.
- To elucidate the mechanism and physiological relevance of diadenosine polyphosphates' effects on Ca2+ ATPase.
Main Methods:
- Enzyme activity was measured spectrophotometrically by assessing ATP hydrolysis in the presence and absence of Ca2+.
- Varying concentrations of ATP and diadenosine polyphosphates were used to determine enzyme kinetics.
Main Results:
- Diadenosine polyphosphates significantly increased Ca2+ ATPase activity.
- The stimulatory effect was more pronounced with Ap5A and Ap6A compared to Ap3A and Ap4A.
- Kinetic analysis indicated a non-competitive, allosteric activation mechanism by diadenosine polyphosphates.
Conclusions:
- Diadenosine polyphosphates act as allosteric activators of Ca2+ ATPase.
- This activation may play a role in modulating cytosolic free Ca2+ concentrations and Ca2+ ATPase function.
- These findings suggest a physiological mechanism for regulating calcium homeostasis by diadenosine polyphosphates.