Understanding Enzyme Superfamilies

We have described four superfamilies of enzymes where the members within each catalyze different overall reactions using broadly varied substrates. Within each superfamily, the different overall reactions are facilitated by a common mechanistic strategy that can be rationalized in the context of the structural scaffold. Although space limitations prevent their discussion, a number of additional superfamilies have been described in which these principles appear to obtain. Analyses of the relationships between structure and function in all of these superfamilies suggest two general conclusions regarding the evolution of new catalytic activities.