Irreversible conversion of delta-1-pyrroline-5-carboxylate (P5C), derived either from proline or ornithine, to glutamate. This is a necessary step in the pathway interconnecting the urea and tricarboxylic acid cycles. The preferred substrate is glutamic gamma-semialdehyde, other substrates include succinic, glutaric and adipic semialdehydes. 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. Homodimer. Highest expression is found in liver followed by skeletal muscle, kidney, heart, brain, placenta, lung and pancreas. The disease is caused by variants affecting the gene represented in this entry. Belongs to the aldehyde dehydrogenase family.