A set of chemical reactions that require a metabolite to synthesize more of that metabolite is an autocatalytic cycle. Such metabolic designs must meet specific conditions to support stable fluxes, hence avoiding depletion of intermediate metabolites. Here we show that most of the reactions in central carbon metabolism are part of compact autocatalytic cycles. As such, they are subjected to constraints that may seem irrational: the enzymes of branch reactions out of the cycle must be overexpressed and the affinity of these enzymes to their substrates must be relatively low. We use recent quantitative proteomics and fluxomics measurements to show that the above conditions hold for all functioning cycles in central carbon metabolism of E.coli. This work demonstrates that the topology of a metabolic network can shape kinetic parameters of enzymes and lead to apparently reduced enzyme efficiency.