Bifunctional enzyme that converts glutamate to glutamate 5- semialdehyde, an intermediate in the biosynthesis of proline, ornithine and arginine. {ECO:0000269|PubMed:10037775, ECO:0000269|PubMed:11092761, ECO:0000269|PubMed:26297558, ECO:0000269|PubMed:26320891, ECO:0000269|PubMed:39506109}. This is the function of Ensembl gene identifier ENSG00000059573 (ALDH18A1, aldehyde dehydrogenase 18 family member A1).