Complex that carries out the oxidative decarboxylation of pyruvate to form acetyl-CoA; comprises subunits possessing three catalytic activities: pyruvate dehydrogenase (E1), dihydrolipoamide S-acetyltransferase (E2), and dihydrolipoamide dehydrogenase (E3). Usually contains fewer subunits than its eukaryotic counterpart; for example, the E. coli complex contains 12 E1 dimers, 8 E2 trimers, and 6 E3 dimers arranged in highly symmetric cubic order.