Catalyzes the E1 and E2 reactions as part of 2-oxoglutarate dehydrogenase (ODH) activity, to convert 2-oxoglutarate to succinyl-CoA and CO(2). OdhA has reductase activity with 2-oxoglutarate but does not react with pyruvate, and also displays transsuccinylase but no transacetylase activity. Since OdhA is not lipoylated, the succinyltransferase activity of its E2 domain is dependent on lipoyl residues of the acetyltransferase AceF. (R)-N(6)-lipoyl-L-lysyl-[dihydrolipoyllysine-residue succinyltransferase] + 2-oxoglutarate + H(+) = (R)-N(6)-(S(8)-succinyldihydrolipoyl)-L-lysyl-[dihydrolipoyllysine-residue succinyltransferase] + CO2 (R)-N(6)-dihydrolipoyl-L-lysyl-[2-oxoglutarate dehydrogenase complex component E2] + succinyl-CoA = (R)-N(6)-(S(8)-succinyldihydrolipoyl)-L-lysyl-[2-oxoglutarate dehydrogenase complex component E2] + CoA Inhibited by unphosphorylated OdhI, but not by phosphorylated OdhI. Carbohydrate metabolism; tricarboxylic acid cycle; succinyl-CoA from 2-oxoglutarate (dehydrogenase route): step 1/1. Homodimer (By similarity). Part of an unusual ODH/PDH supercomplex, consisting of AceE (E1), AceF (E2), and Lpd (E3) together with OdhA (E1+E2). Interacts with the FHA domain of unphosphorylated OdhI via its C-terminal dehydrogenase domain. OdhA is a fusion protein with two major domains exhibiting structural features of an E1 and E2 protein, and a short sequence stretch of E1 localized at the N-terminus, which is connected by a linker region to the rest of the protein. Deletion of individual parts of odhA show that all parts of odhA are required for a functional tricarboxylic acid cycle in C.glutamicum; the ODH activity is in fact completely abolished in each of these mutants, and the PDH activity is significantly reduced, which could indicate that the overall structure of the supercomplex is disturbed. Strains lacking this gene completely lack 2-oxoglutarate dehydrogenase activity. Deletion of odhA also causes L-glutamate overproduction and accumulation during growth. Is non-lipoylated. In contrast, the E2 component AceF is the prominent lipoylated protein in C.glutamicum. In the N-terminal section; belongs to the alpha-ketoglutarate dehydrogenase family. In the C-terminal section; belongs to the 2-oxoacid dehydrogenase family. Extended N-terminus. Extended N-terminus.