Localization of enzymes in E. coli pathways. A. Images of localized enzymes from glycolysis and TCA cycle. In the diagram, indicated in green are the reactions for which the associated enzyme localizes and in blue reactions where enzymes are diffuse. Triangle indicates amino-acids, square carbohydrates, circles for other metabolites. B. Log-log plot of the number of localized enzymes against the number of reactions in a pathway – pathway length– for the 59 pathways showing localized enzymes (Pearson correlation is 0.98). Inside. Distribution of the ratio of pathway length to number of localized enzymes, mean value is 7.1.