Involved in the biosynthesis of L-aspartate-beta-semialdehyde which is a central intermediate in the biosynthesis of different amino acids (L-lysine, L-methionine, L-threonine). Catalyzes the phosphorylation of the beta-carboxyl group of L-aspartate to yield 4-phospho-L-aspartate. ATP + L-aspartate = 4-phospho-L-aspartate + ADP Allosterically feedback inhibited by L-lysine and L-threonine individually and also subject to a concerted feedback inhibition by these amino acids. Optimum pH is between 7.9 and 8.4. 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-threonine biosynthesis; L-threonine from L-aspartate: step 1/5. Repressed by L-methionine. Belongs to the aspartokinase family.