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] kcat is 452 min(-1) for 2-oxoglutarate as substrate. kcat is 144 min(-1) for pyruvate as substrate. kcat is 93 min(-1) for 2-oxobutyrate as substrate. Optimum pH is between 7-8. Optimum temperature is 70 degrees Celsius. Heterodimer composed of an alpha and a beta subunit. The Tyr-Pro-Ile-Thr-Pro (YPITP) motif is important for the turnover of the reaction, presumably through its flexibility and mobility.