Change in Heat Capacity for Enzyme Catalysis Determines Temperature Dependence of Enzyme Catalyzed Rates

The increase in enzymatic rates with temperature up to an optimum temperature (T-opt) is widely attributed to classical Arrhenius behavior, with the decrease in enzymatic rates above T-opt ascribed to protein denaturation and/or aggregation. This account persists despite many investigators noting that denaturation is insufficient to explain the decline in enzymatic rates above T-opt. Here we show that it is the change in heat capacity associated with enzyme catalysis (Delta C-p(double dagger)) and its effect on the temperature dependence of Delta G(double dagger) that determines the temperature dependence of enzyme activity. Through mutagenesis, we demonstrate that the T-opt of an enzyme is correlated with Delta C-p(double dagger) and that changes to Delta C-p(double dagger) are sufficient to change T-opt without affecting the catalytic rate. Furthermore, using X-ray crystallography and molecular dynamics simulations we reveal the molecular details underpinning these changes in Delta C-p(double dagger). The influence of Delta C-p(double dagger) on enzymatic rates has implications for the temperature dependence of biological rates from enzymes to ecosystems.