In vitro, catalyzes the dehydration of trans-3-hydroxy-L-proline (t3LHyp) to Delta(1)-pyrroline-2-carboxylate (Pyr2C), albeit with very low efficiency. The physiological substrate may be different. Displays neither trans-4-hydroxy-L-proline (t4LHyp) epimerase nor proline racemase activity. trans-3-hydroxy-L-proline = 1-pyrroline-2-carboxylate + H2O kcat is 0.15 sec(-1) for t3LHyp dehydration. The reaction is too slow to measure KM for t3LHyp. Belongs to the proline racemase family.