1.5.5.2 L-proline + a quinone - 1.5.5.2 L-proline + a quinone the reverse reaction is catalyzed by pyrroline-5-carboxylate reductase, EC 1.5.1.2 1.5.5.2 L-proline + acceptor - 1.5.5.2 L-proline + acceptor the bifunctional enzyme catalyzes the oxidation of proline in two steps. (S)-1-Pyrroline-5-carboxylate, the product of the first reaction is in spontaneous equilibrium with its tautomer L-glutamate gamma-semialdehyde: (1) L-proline + acceptor = (S)-1-pyrroline-5-carboxylate + reduced acceptor, (2) L-glutamate 5-semialdehyde + NAD+ + H2O = L-glutamate + NADH + H+ 1.5.5.2 L-proline + acceptor + H2O - 1.5.5.2 L-proline + acceptor + H2O PutA flavoprotein plays multiple roles in proline catabolism by functioning as a membrane-associated bi-functional enzyme and a transcriptional repressor of proline utilization genes 1.5.5.2 L-proline + acceptor + H2O the enzyme catalyzes the first step of proline catabolism 1.5.5.2 L-proline + oxidized phenazine methosulfate -