As said before, MCD presents a half of the sites reactivity, due to the fact that each heterodimer has two different structural conformations: B state (bound), in which the substrate is united; and U conformation (unbound), where the substrate union isn't allowed. According to this, the half of the sites mechanism might present a consumption of catalytic energy. Nevertheless, the conformational change produced in a subunit when changing from the B state to the U state (which produces the release of the product) coincides with the formation of a new union site in the active site of the neighbour subunit when changing from the U stat to B state. As a result, the conformational changes synchronised in the pair of subunits facilitates the catalysis despite the reduction of the number of available active sites.