Catalytic efficiency and structural properties of invertebrate muscle pyruvate kinases: Correlation with body temperature and oxygen consumption rates

Abstract

1. Structural, kinetic and thermodynamic activation properties of muscle pyruvate kinases from invertebrate species adapted to different thermal environments were examined. 2. Structural rigidity, as estimated by ammonium sulfate precipitation and heat inactivation temperature, is positively correlated with acclimatization temperature of the organism (Fig. 1). 3. Km-values for PEP are hardly influenced by experimental temperatures within the normal temperature range of the species (Fig. 2). A good correlation, however, exists betweenKm-values and the capacity of tissues for aerobic glycolysis (Fig. 3). 4. All pyruvate kinases can exist in two (or more) temperature-dependent conformational states. Sizes of ΔH≠-values are correlated with the species' acclimatization temperature (Fig. 6) but not with the temperature variability in the cells (Fig. 7). 5. A correlation exists between the free energy of activation ΔG≠, body temperatures and the capacity of muscles for aerobic glycolysis (Table 2).