Temperature and the regulation of enzyme activity in poikilotherms : regulatory properties of fish fructose-1, 6-diphosphatase ...

• Main Author: Behrisch, Hans Werner
• Format: Text
• Language: English
• Published: University of British Columbia 2011
• Subjects: Oncorhynchus gorbuscha; Pink salmon
• Online Access: https://dx.doi.org/10.14288/1.0104155; https://doi.library.ubc.ca/10.14288/1.0104155

The regulatory properties of fructose 1,6-diphosphatase (FDPase) from liver of rainbow trout (Salmo gairdneri), South American lungfish (Lepidosiren paradoxa) and migrating pink salmon (Oncorhynchus gorbuscha) were examined over the physiological temperature ranges of the organisms. In rainbow trout saturation curves for substrate (fructose 1,6-diphosphate), and a cofactor (Mg²⁺ ) are sigmoidal, and the evidence suggests cooperative interaction between the binding sites for these ligands. The affinity of the trout enzyme is approximately 50-to 100-fold higher for Mn²⁺ than for Mg²⁺ and the Mn²⁺ saturation curve is hyperbolic. The enzyme is inhibited by Ca²⁺ and Zn²⁺ and this inhibition appears to be competitive with respect to cofactor. The trout FDPase has an alkaline pH optimum and high pH values enhance FDPase affinity for cofactor. Low concentrations of 5'AMP inhibit the rainbow trout FDPase and the enzyme-AMP interaction is sensitive to temperature; thus, Ki for AMP at 25° is approximately 30-fold ...