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 lung, skeletal muscle and brain, to a lesser extent in heart and kidney, and weakly in liver, placenta and pancreas. During p53/TP53-induced apoptosis. The disease is caused by variants affecting the gene represented in this entry. Disease susceptibility is associated with variants affecting the gene represented in this entry. Belongs to the proline oxidase family. Artifact. Missing internal sequence that doesn't correspond to an exon-intron boundary. Intron retention. Includes intronic sequence at the 5' end.