The TCA cycle and the enzymatic connections of its intermediates. The only difference between the Bge and the Pam metabolic networks is the absence of citrate synthase, aconitase and isocitrate dehydrogenase in the latter (asterisk labelled steps). Note that, with the exception of their participation in the TCA cycle, citrate and isocitrate are isolated nodes in the network. Each enzymatic step is indicated by its EC number. Double arrows indicate reversible reactions, single arrows indicate irreversible reactions.