Structurally characterized enzymes in the RuBisCO superfamily are dimers with an active site located at the interface of the N-terminal alpha+beta domain of one polypeptide and the C-terminal TIM beta/alpha-barrel of the second polypeptide. Though most of the enzymes in the superfamily are thought to function as D-Ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO), a smaller number of enzymes, termed the RuBisCO-like proteins, do not catalyze carboxylation reactions. Despite these differences, superfamily enzymes share a common active site architecture used to stabilize an enolate intermediate.