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 (By similarity). 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. Acetylation of Lys-98, Lys-113 and Lys-401 is observed in liver mitochondria from fasted mice but not from fed mice. Belongs to the aldehyde dehydrogenase family.