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Rat liver phosphorylase kinase. Stimulation by heparin
The Journal of Biological Chemistry
|December 25, 1981
Summary
Heparin rapidly stimulates rat liver phosphorylase kinase activity, similar to phosphorylation. This effect is reversed by antithrombin III and reduced by MgATP, suggesting a novel activation mechanism for this key metabolic enzyme.
Area of Science:
- Biochemistry
- Enzymology
Background:
- Phosphorylase kinase is a key regulator of glycogen metabolism.
- Understanding its regulation is crucial for metabolic research.
Purpose of the Study:
- To investigate the effect of heparin on rat liver phosphorylase kinase activity.
- To elucidate the mechanism of heparin-mediated enzyme stimulation.
Main Methods:
- Enzyme activity assays were performed on rat liver phosphorylase kinase.
- The effects of varying heparin concentrations and other factors were analyzed.
- Kinetic studies were conducted in the presence and absence of heparin.
Main Results:
- Heparin significantly increased phosphorylase kinase activity (up to 7-fold) at low concentrations.
- The stimulation was rapid (within 15 s) and reversible by antithrombin III.
- Heparin's effect was diminished by prior enzyme activation with MgATP and inversely related to phosphorylase b concentration.
Conclusions:
- Heparin acts as a potent, reversible stimulator of a low-activity form of liver phosphorylase kinase.
- This stimulation mimics activation by phosphorylation, indicating a novel regulatory pathway.
- The findings provide new insights into the complex regulation of glycogenolysis.