Converts proline to delta-1-pyrroline-5-carboxylate. a quinone + L-proline = (S)-1-pyrroline-5-carboxylate + a quinol + H(+) Amino-acid degradation; L-proline degradation into L-glutamate; L-glutamate from L-proline: step 1/2. Expressed in the vascular tissue and in the abscission zone of petals, sepals, stamina, pistils and siliques. Not detected in petioles. Strongly expressed in senescent leaves. Down-regulated by high succrose; via the repression of bZIP11. Up-regulated by proline and salt or drought stress. No visible phenotype when grown under normal conditions. No proline hypersensitivity. Belongs to the proline oxidase family.