Catalyzes the conversion of L-ornithine into L-proline with release of ammonia. Is involved in the utilization of octopine, a catabolic pathway that proceeds through L-arginine and L-ornithine to L-proline. Octopine is a predominant opine in plant cells transformed with Ti plasmid pTiAch5. L-ornithine = L-proline + NH4(+) Is inhibited by L-proline and L-lysine. Is not activated by small concentrations of L-arginine, and is even inhibited by about 50% at 0.5 mM L-arginine. Optimum pH is 8.0-8.5. Optimum temperature is 30-35 degrees Celsius. Amino-acid biosynthesis; L-proline biosynthesis; L-proline from L-ornithine: step 1/1. Is induced by octopine. Is part of the occ operon. Belongs to the ornithine cyclodeaminase/mu-crystallin family.