Involved in the catabolism of oxalate and in the adapatation to low pH. ACOCT serves to prime the oxalate-induced acid tolerance response (ATR) cycle by producing substrate for oxalyl-CoA decarboxylase (OXC) and formyl-coenzyme A transferase (FCOCT). Catalyzes the reversible conversion of acetyl-CoA and oxalate to oxalyl-CoA and acetate. It can also use formyl-CoA and oxalate to produce oxalyl-CoA and formate with significantly reduced specific activity. acetyl-CoA + oxalate = acetate + oxalyl-CoA kcat is 1.8 sec(-1) for the CoA-transferase activity with oxalate as substrate (at pH 6.7 and 25 degrees Celsius). kcat is 2 sec(-1) for the CoA-transferase activity with acetyl-CoA as substrate (at pH 6.7 and 25 degrees Celsius). Homodimer. Belongs to the CoA-transferase III family.