Multiple thermal discontinuities in glucose-6-phosphatase activity.

The temperature dependence of glucose-6-phosphatase (D-glucose-6-phosphate phosphohydrolase EC 3.1.3.9) was studied in rat liver and kidney microsomal fractions. Arrhenius plots were non-linear and showed four distinct discontinuities in enzyme activity over the temperature range 2-41 degrees C. The discontinuities occurred at approx. 39, 30, 20 and 12 degrees C in the liver and were similar to this in the kidney. Changes in the energy of activation for the enzyme were noted at approx. 20 degrees C in both tissues. The multiple discontinuities in glucose-6-phosphatase activity are viewed as a reflection of complex reorganization and/or change in physical state of the membrane components, primarily lipid.