Catalyzes the reversible interconversion of L- and D-proline (PubMed:5722267, PubMed:24314397). Likely functions as the proline racemase necessary for D-proline generation in order to discriminate it from the L-proline used for protein synthesis (PubMed:20937090). L-proline = D-proline Inhibited by pyrrole-2-carboxylate in vitro. kcat is 64 sec(-1) with L-proline as substrate. Differs from other amino acid racemases in that no requirement for pyridoxal phosphate could be shown. Belongs to the proline racemase family.