L-homoserine + NADP(+) = H(+) + L-aspartate 4-semialdehyde + NADPH L-homoserine + NAD(+) = H(+) + L-aspartate 4-semialdehyde + NADH Feedback inhibition by threonine. Optimum pH is 6.0. 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 3/5. Belongs to the homoserine dehydrogenase family.