Elsevier

Methods in Enzymology

Volume 2, 1955, Pages 541-543
Methods in Enzymology

[83] Glucose-6-phosphatase from liver: Glucose6P+H2OGlucose+ PO4

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This chapter discusses the determination of glucose-6-phosphatase from liver. The assay method is based on the incubation of the specific substrate with the enzyme and determination of the liberated orthophosphate. Attempts to purify the enzyme have been limited by its extreme instability and its insolubility. It appears to be bound to the microsomes. These can be sedimented from isotonic sucrose at 30,000 X g, or agglutinated at pH 5.4. The precipitated microsomes may be washed at this pH to remove phosphoglucomutase. Hexose isomerase, ATPase, AMPase, and a feeble glycerophosphatase are not removed by the washing. Solubilization by means of detergents or bile salts has not been attempted. The enzyme is apparently specific for G-6-P. After removal of the mutase by washing, G-1-P is split not at all, and fructose disappears in the same proportion that inorganic phosphate is liberated from F-6-P. Galactose phosphate and mannose phosphate have not been tested. It has an optimum pH of 6.5 and appears to require no metallic activator. Molybdate and arsenate inhibit to some extent; fluoride gives very inconsistent results.

References (4)

  • M.A. Swanson

    J. Biol. Chem.

    (1950)
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