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Glucose-6-phosphatase specificity after membrane solubilization by detergent treatment
A Ajzannay1, C Minassian, J P Riou
1INSERM U. 197, Faculté de Médecine Alexis Carrel, Lyon, France.
Journal of Biochemistry
|December 1, 1994
Summary
Glucose-6-phosphatase (Glc6Pase) in detergent-treated liver microsomes shows limited specificity for glucose-6-phosphate (Glc6P) over mannose-6-phosphate (Man6P). The liver membrane plays a crucial role in Glc6Pase
Area of Science:
- Biochemistry
- Enzymology
- Molecular Biology
Background:
- Glucose-6-phosphatase (Glc6Pase) is a key liver microsomal enzyme.
- Intact membranes confer high specificity for glucose-6-phosphate (Glc6P).
- Detergent-treated Glc6Pase hydrolyzes both Glc6P and mannose-6-phosphate (Man6P) similarly.
Purpose of the Study:
- To investigate the substrate specificity of detergent-treated Glc6Pase.
- To determine if Glc6Pase retains any specificity for Glc6P after detergent treatment.
- To elucidate the role of the membrane in Glc6Pase specificity.
Main Methods:
- Competition experiments using radiolabeled Glc6P and Man6P.
- Varying concentrations of unlabeled Glc6P and Man6P as competitors.
- Measuring the rate of hydrolysis of radiolabeled substrates.
Main Results:
- Detergent-treated Glc6Pase showed significantly higher hydrolysis rates for Glc6P in the presence of Man6P compared to Glc6P as a competitor.
- Similarly, hydrolysis rates for Man6P were higher when Man6P was the competitor versus Glc6P.
- These results indicate a limited but present specificity for Glc6P even after detergent treatment.
Conclusions:
- Detergent treatment of liver microsomes partially unmasks Glc6Pase's substrate specificity.
- The liver microsomal membrane is essential for establishing the full physiological specificity of Glc6Pase.
- Understanding Glc6Pase kinetics is crucial for metabolic research.