Ribulose-Phosphate 3-Epimerase (RPE) is a member of the Ribulose-Phosphate 3-Epimerase family. RPE exists as a homodimer and catalyzes the reversible epimerization of D-ribulose 5-phosphate to D-xylulose 5-phosphate. RPE binds one divalent metal cation per subunit and contains tightly bound Fe2+ when produced in E. coli, but the physiological cofactor may be Co2+, Mn2+ or Zn2+. It has been shown that RPE participates in 3 metabolic pathways: pentose phosphate pathway, pentose and glucuronate interconversions, and carbon fixation.