To complete the scaffold-based structural analysis, in Figure the fraction of scaffolds shared between target classes is depicted, which is also a measure of the structural similarity shared between the metabolites of the different target classes. Scaffolds are shared the most between "Cytochrome P450" and "Enzyme other" (0.57); "Cytochrome P450" and "Kinase" (0.56); and "Hydrolase" and "Oxidoreductase" (0.55). Also between "Epigenetic regulator" and "Transferase" (0.533), and the former and "Other" (0.52). The target classes with the highest marginal sum of fractions of shared scaffolds are "Cytochrome P450", followed by "Kinase", and "Enzyme other".