Catalyzes the transfer of CoA from acetoacetyl-CoA to acetate, butyrate and propionate (PubMed:2719476, PubMed:2383002). Shows also low activity with valerate, isobutyrate and crotonate (PubMed:2719476). Plays an important role in the metabolic shift between the acid-producing and solvent-forming states of C.acetobutylicum (PubMed:2383002). Acts mainly to detoxify the medium by removing the acetate and butyrate excreted earlier in the fermentation (PubMed:2719476, PubMed:2383002). acetoacetate + butanoyl-CoA = acetoacetyl-CoA + butanoate acetoacetate + acetyl-CoA = acetate + acetoacetyl-CoA The acetate and butyrate conversion reactions are inhibited in vitro by physiological levels of acetone and butanol. Shows at least 80% of maximal activity from pH 5.9 to greater than 7.8 for acetate conversion. Heterotetramer composed of two alpha subunits (CtfA) and two beta subunits (CtfB). Transcriptionally induced or derepressed before the onset of solventogenesis. Belongs to the 3-oxoacid CoA-transferase subunit B family.