Catalyzes the NAD-dependent reduction of succinylglutamate semialdehyde into succinylglutamate. H2O + N-succinyl-L-glutamate 5-semialdehyde + NAD(+) = 2 H(+) + N-succinyl-L-glutamate + NADH Amino-acid degradation; L-arginine degradation via AST pathway; L-glutamate and succinate from L-arginine: step 4/5. Belongs to the aldehyde dehydrogenase family. AstD subfamily. Truncated C-terminus.