Releases the N-terminal proline from various substrates. Cleaves specifically Pro-betaNA and small peptides containing proline at the amino terminal. No activity against hydroxyproline-betaNA. Release of N-terminal proline from a peptide. Optimum pH 8.0. Maximum activity at 42 degrees Celsius. Stable at temperatures up to 44 degrees Celsius, showing 50% of activity after incubation at this temperature for 15 minutes (at pH 8.0). Monomer. Belongs to the peptidase S33 family.