Temperature adaptation of enzymes: A proposed molecular basis for the different catalytic efficiencies of enzymes from ectotherms and endotherms

Abstract

1. 1. A number of enzymic reactions of ectotherms have lower values for the free energy, the enthalpy and the entropy of activation than the homologous reactions of birds and mammals. 2. 2. Differences in the magnitudes of the activation parameters, which lead to marked differences in the catalytic efficiencies of the homologous enzymes, can be accounted for on the basis of increased weak bond formation during the generation of the activated enzyme-substrate complex in ectothermic systems.