Releases the N-terminal proline from various substrates. Hydrolyzes only di- and tripeptides with proline in the first position. Release of N-terminal proline from a peptide. Optimum pH is 7.5. At pH values above 7.5, the activity sharply decreases. Optimum activity at 40 degrees Celsius. Homodimer. Belongs to the peptidase S33 family.