N-acetyl-L-glutamate 5-semialdehyde + NADP(+) + phosphate = H(+) + N-acetyl-L-glutamyl 5-phosphate + NADPH ATP + N-acetyl-L-glutamate = ADP + N-acetyl-L-glutamyl 5-phosphate Amino-acid biosynthesis; L-arginine biosynthesis; N(2)-acetyl-L-ornithine from L-glutamate: step 2/4. Amino-acid biosynthesis; L-arginine biosynthesis; N(2)-acetyl-L-ornithine from L-glutamate: step 3/4. In the N-terminal section; belongs to the acetylglutamate kinase family. In the C-terminal section; belongs to the NAGSA dehydrogenase family.