Important for the use of proline as a sole carbon and energy source or a sole nitrogen source. H2O + L-glutamate 5-semialdehyde + NAD(+) = 2 H(+) + L-glutamate + NADH Amino-acid degradation; L-proline degradation into L-glutamate; L-glutamate from L-proline: step 2/2. The expression of the putBCP operon is induced in a PutR-dependent fashion by very low concentrations of L-proline in the growth medium. CodY represses the operon by displacing PutR from DNA. Deletion of the putBCP operon abolishes L-proline utilization. Belongs to the aldehyde dehydrogenase family. RocA subfamily.