Involved in the degradation of L-arabinose (PubMed:13890280). Catalyzes the interconversion of L-ribulose 5-phosphate (LRu5P) and D-xylulose 5-phosphate (D-Xu5P) via a retroaldol/aldol mechanism (carbon-carbon bond cleavage analogous to a class II aldolase reaction). L-ribulose 5-phosphate = D-xylulose 5-phosphate Binds 1 zinc ion per subunit (PubMed:9548961, PubMed:10769139, PubMed:11732895, PubMed:11732896). Also able to use cobalt and manganese ions, but less efficiently (PubMed:10769139). Inhibited by glycolohydroxamate at concentration above 0.1 mM. kcat is 20.4 sec(-1) for L-ribulose 5-phosphate (LRu5P) as substrate (PubMed:9548961). kcat is 19.4 sec(-1) for L-ribulose 5-phosphate (LRu5P) as substrate (PubMed:11732896). kcat is 17.3 sec(-1) for L-ribulose 5-phosphate (LRu5P) as substrate (PubMed:10769139). kcat is 10.6 sec(-1) for L-ribulose 5-phosphate (LRu5P) as substrate (at pH 7) (PubMed:10769138). kcat is 4.23 sec(-1) for L-ribulose 5-phosphate (LRu5P) as substrate (at pH 5.5) (PubMed:10769138). Optimum pH is 7. Carbohydrate degradation; L-arabinose degradation via L-ribulose; D-xylulose 5-phosphate from L-arabinose (bacterial route): step 3/3. Homotetramer. Induced by arabinose. Transcription is dependent on the transcription factor AraC, the cAMP receptor protein (CRP) and cAMP (PubMed:328165, PubMed:2962192, PubMed:7768852). Also induced by L-lyxose (PubMed:10913097). Cells lacking this gene accumulate large amount of L-ribulose 5-phosphate when incubated with L-arabinose. Belongs to the aldolase class II family. AraD/FucA subfamily.