Dehydrogenase that converts trans-4-L-hydroxyproline to delta-1-pyrroline-3-hydroxy-5-carboxylate (Hyp) using ubiquinone-10 as the terminal electron acceptor. Can also use proline as a substrate but with a very much lower efficiency. Does not react with other diastereomers of Hyp: trans-4-D-hydroxyproline and cis-4-L-hydroxyproline. Ubiquininone analogs such as menadione, duroquinone and ubiquinone-1 react more efficiently than oxygen as the terminal electron acceptor during catalysis. a quinone + trans-4-hydroxy-L-proline = (3R,5S)-1-pyrroline-3-hydroxy-5-carboxylate + a quinol + H(+) a quinone + L-proline = (S)-1-pyrroline-5-carboxylate + a quinol + H(+) Hydroproxyproline dehydrogenase activity is inhibited by THFA,(1R,3R)3-OH-cyclopentane-COOH and 5-OH-1H-pyrazole-3-COOH. kcat with trans-4-L-hydroxyproline (Hyp) and ubiquinone-1 is 0.19 sec(-1). Proline is unable to saturate PRODH2 at least up to 750mM. kcat/KM with proline and ubiquinone-10: 0.075 M(-1)/sec. kcat with oxygen, duroquinone, menadione and CoQ1 and with trans-4-L-hydroxyproline are 0.002 sec(-1), 0.27 sec(-1), 0.28 sec(-1) and 0.19 sec(-1), respectively. Belongs to the proline oxidase family.