Thermodynamic trajectory of enzyme evolution

The trajectory of enzyme evolution is estimated from the relationship between the overall enthalpy of activation and overall entropy of activation. As evolution proceeds, the trajectory passes a turning point and then go toward diffusion-controlled region. Thus, the following two possibilities are put forth as candidates of a goal of evolution. One is that evolution will stop at a turning point, where specificity of a reaction is highest. The other is that the ultimate goal of evolution is the diffusion-controlled reaction, where catalytic efficiency is highest.