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Quinone reductase enzyme activity in pancreatic islets
1Childrens Diabetes Center, University of Wisconsin Medical School, Madison 53706.
Endocrinology
|September 1, 1991
Summary
Coenzyme Q0 stimulates insulin release, and its reductase enzyme is present in pancreatic islets. This enzyme
Area of Science:
- Biochemistry
- Endocrinology
- Cell Biology
Background:
- Water-soluble quinones, such as coenzyme Q0 (CoQ0), influence insulin secretion.
- Dicumarol, a quinone reductase inhibitor, impairs glucose-stimulated insulin release in pancreatic islets, suggesting a role for this enzyme in insulin physiology.
Purpose of the Study:
- To characterize quinone reductase activity and localization within pancreatic islets.
- To investigate the enzyme's substrate specificity and inhibition patterns.
Main Methods:
- Enzyme activity assays using various quinone substrates and coenzymes (NADPH, NADH).
- Inhibition studies with dicumarol, chlorpromazine, and T3.
- Subcellular fractionation to determine enzyme localization.
Main Results:
- Quinone reductase activity was primarily found in the cytosol (>90%), with the highest specific activity in the microsomal fraction.
- Enzyme activity showed a preference for CoQ0 and durohydroquinone.
- Dicumarol, chlorpromazine, and T3 were more potent inhibitors when NADPH was the coenzyme.
- Pancreatic islets exhibited the second-highest quinone reductase activity after liver.
Conclusions:
- Quinone reductase is present and active in pancreatic islets.
- The enzyme's characteristics in islets resemble those found in liver tissue.
- Quinone reductase activity may play a significant role in the physiological regulation of insulin secretion.