Although PDC does not directly require O2 the purpose of it is to link glycolysis to the citric acid cycle which only occurs in a an aerobic state. The purpose of the PDC is to create more ATP (via the citric acid cycle) and so when there is a lot of ATP it will be inhibited (we don't need to make more energy) and when there is a lot of AMP (not a lot of ATP) it will be activated as we need more energy. Hope this helps!