The 2-oxoglutarate dehydrogenase complex consists of this thiamine pyrophosphate-binding subunit (E1), dihydrolipoamide succinyltransferase (E2), and lipoamide dehydrogenase (E3). The E1 ortholog from Corynebacterium glutamicum is unusual in having an N-terminal extension that resembles the dihydrolipoamide succinyltransferase (E2) component of 2-oxoglutarate dehydrogenase. [Energy metabolism, TCA cycle]