The enzyme, which belongs to the RuBisCO-like-protein (RLP) superfamily, has been characterized from several bacterial species. It participates in the degradation of D-apionate. The reaction is initiated by decarboxylation to generate a stabilized enediolate intermediate, with the sequestered CO2 carboxylating the adjacent enediolate carbon atom. The resulting 3-ketose-1-phosphate intermediate is hydrolysed, as in the authentic RuBisCO-catalysed reaction, to generate glycolate and 3-phospho-D-glycerate. Stereospecificity of 3-oxoisoapionate 4-phosphate has not been determined.