L-homoserine + NADP(+) = H(+) + L-aspartate 4-semialdehyde + NADPH L-homoserine + NAD(+) = H(+) + L-aspartate 4-semialdehyde + NADH ATP + L-aspartate = 4-phospho-L-aspartate + ADP Amino-acid biosynthesis; L-lysine biosynthesis via DAP pathway; (S)-tetrahydrodipicolinate from L-aspartate: step 1/4. Amino-acid biosynthesis; L-methionine biosynthesis via de novo pathway; L-homoserine from L-aspartate: step 1/3. Amino-acid biosynthesis; L-methionine biosynthesis via de novo pathway; L-homoserine from L-aspartate: step 3/3. Amino-acid biosynthesis; L-threonine biosynthesis; L-threonine from L-aspartate: step 1/5. Amino-acid biosynthesis; L-threonine biosynthesis; L-threonine from L-aspartate: step 3/5. Homotetramer. Aspartokinase I-homoserine dehydrogenase I and aspartokinase III also catalyze the same reaction(s). In the N-terminal section; belongs to the aspartokinase family. In the C-terminal section; belongs to the homoserine dehydrogenase family.