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Diadenosine tetraphosphate activates cytosol 5'-nucleotidase
Biochemical and Biophysical Research Communications
|July 16, 1986
Summary
Diadenosine tetraphosphate (Ap4A) significantly activates cytosol 5'-nucleotidase from Artemia embryos, enhancing IMP hydrolysis. This potent activator requires much lower concentrations than previously known activators like ATP.
Area of Science:
- Biochemistry
- Enzymology
Background:
- Cytosol 5 -nucleotidase plays a role in nucleotide metabolism.
- Diadenosine tetraphosphate (Ap4A) is a dinucleotide with signaling functions.
- Previous studies identified ATP as a weaker activator of this enzyme.
Purpose of the Study:
- To investigate the effect of diadenosine tetraphosphate (Ap4A) on cytosol 5 -nucleotidase activity.
- To compare the activating potential of Ap4A with ATP.
- To explore the activation of rat liver cytosol 5 -nucleotidase by Ap4A.
Main Methods:
- Enzyme kinetics assays were performed using varying concentrations of IMP and Ap4A.
- Kinetic parameters, including Km (S 0.5) and Vmax, were determined.
- Comparative activation studies with ATP were conducted.
Main Results:
- Ap4A increased the hydrolysis rate of IMP by up to 7-fold at 10 microM concentrations.
- Half-maximal activation was achieved with 5 microM Ap4A.
- Ap4A decreased the Km (S 0.5) values for IMP, GMP, AMP, XMP, and CMP by approximately 10-fold, without affecting Vmax.
- Ap4A demonstrated significantly higher potency as an activator compared to ATP.
Conclusions:
- Diadenosine tetraphosphate (Ap4A) is a potent activator of Artemia embryo cytosol 5 -nucleotidase.
- Ap4A enhances enzyme activity by increasing substrate affinity rather than catalytic rate.
- Ap4A may also activate the homologous enzyme in rat liver, suggesting a conserved regulatory mechanism.