Involved in the catabolism of oxalate and in the adapatation to low pH via the induction of the oxalate-dependent acid tolerance response (ATR). Essential enzyme for the bacterium survival, as it relies on oxalic acid as its sole source of energy. Catalyzes the decarboxylation of oxalyl-CoA to yield carbon dioxide and formyl-CoA. H(+) + oxalyl-CoA = CO2 + formyl-CoA Binds 1 metal ion per subunit. Binds 1 thiamine pyrophosphate per subunit. Inhibited by CoA and activated by ADP. kcat is 88 sec(-1) for decarboxylase activity with oxalyl-CoA as substrate (at pH 6.7 and 30 degrees Celsius). Metabolic intermediate degradation; oxalate degradation; CO(2) and formate from oxalate: step 2/2. Homotetramer; dimer of dimers. The N-terminus is blocked. Belongs to the TPP enzyme family.