Functions in the bile acid 7alpha-dehydroxylation pathway, which forms secondary bile acids via the 7alpha-dehydroxylation of primary bile acids, and is carried out by intestinal anaerobic bacteria. Acts as a bile acid CoA transferase with broad bile acid substrate specificity. Catalyzes the transfer of the CoA moiety of secondary bile acid-CoA compounds to primary bile acids. Can use deoxycholoyl-CoA and allodeoxycholoyl-CoA as bile acid CoA donors and cholate, allocholate and ursodeoxycholate as bile acid CoA acceptors. Shows no activity when lithocholoyl-CoA is used as the CoA donor. cholate + deoxycholoyl-CoA = choloyl-CoA + deoxycholate allodeoxycholoyl-CoA + cholate = allodeoxycholate + choloyl-CoA allocholate + deoxycholoyl-CoA = allocholoyl-CoA + deoxycholate allocholate + allodeoxycholoyl-CoA = allocholoyl-CoA + allodeoxycholate deoxycholoyl-CoA + ursodeoxycholate = deoxycholate + ursodeoxycholoyl-CoA allodeoxycholoyl-CoA + ursodeoxycholate = allodeoxycholate + ursodeoxycholoyl-CoA Lipid metabolism; bile acid biosynthesis. Belongs to the CoA-transferase III family.