OXC belongs to the family of lyases, specifically the carboxy-lyases (decarboxylases), which cleave carbon-carbon bonds. The systematic name of this enzyme class is oxalyl-CoA carboxy-lyase (formyl-CoA-forming). Other names in common use include oxalyl coenzyme A decarboxylase, and oxalyl-CoA carboxy-lyase. This enzyme participates in glyoxylate and dicarboxylate metabolism. It employs one cofactor, thiamin diphosphate (TPP), and plays a key role in catabolism of oxalate, a highly toxic compound that is a product of the oxidation of carbohydrates in many bacteria and plants. Oxalyl-CoA decarboxylase is extremely important for the elimination of ingested oxalates found in human foodstuffs like coffee, tea, and chocolate, and the ingestion of such foods in the absence of Oxalobacter formigenes in the gut can result in kidney disease or even death as a result of oxalate poisoning.

Oxalyl-CoA decarboxylase is hypothesized to be evolutionarily related to acetolactate synthase, a TPP-dependent enzyme responsible for the biosynthesis of branched chain amino acids in certain organisms. Sequence alignments between the two enzymes support this claim, as do the presence of vestigial FAD-binding pockets that play no role in either enzyme’s catalytic activity. The binding of FAD at this site in acetolactate synthase and the binding of ADP at a cognate site in OXC are thought to play roles in the stabilization of the tertiary structures of the proteins. No FAD binding is observed in oxalyl-CoA decarboxylase, but an excess of coenzyme A in the crystal structure has led to the hypothesis that the binding site was co-opted during OXC evolution to bind the CoA moiety of its substrate. Despite their similarities, only oxalyl-CoA decarboxylase is necessary for the formation of ATP in Oxalobacter formigenes, and exogenous ADP has been demonstrated to increase the decarboxylase activity of OXC, but not acetolactate synthase.

...
Wikipedia