ribulose-phosphate 3-epimerase activity

Catalysis of the reaction: D-ribulose 5-phosphate = D-xylulose 5-phosphate.

D-ribulose 5-phosphate epimerase activity, D-ribulose phosphate-3-epimerase activity, D-ribulose-5-P 3-epimerase activity, D-ribulose-5-phosphate 3-epimerase activity, D-ribulose-5-phosphate epimerase activity, D-xylulose-5-phosphate 3-epimerase activity, erythrose-4-phosphate epimerase activity, erythrose-4-phosphate isomerase activity, pentose-5-phosphate 3-epimerase activity, phosphoketopentose 3-epimerase activity, phosphoketopentose epimerase activity, phosphoribulose epimerase activity, ribulose 5-phosphate 3-epimerase activity, ribulose-phosphate 3-epimerase activity, xylulose phosphate 3-epimerase activity