Catalyzes the coenzyme A-dependent oxidative decarboxylation of different 2-oxoacids such as 2-oxoglutarate, pyruvate and 2-oxobutyrate to form their CoA derivatives. a 2-oxocarboxylate + CoA + 2 oxidized [2Fe-2S]-[ferredoxin] = an acyl-CoA + CO2 + H(+) + 2 reduced [2Fe-2S]-[ferredoxin] Binds 1 [4Fe-4S] cluster per subunit. Binds 1 thiamine pyrophosphate per subunit. Binds 1 Mg(2+) per subunit. Heterodimer composed of an alpha and a beta subunit.