Specifically catalyzes the NAD or NADP-dependent dehydrogenation of L-aspartate to iminoaspartate. H2O + L-aspartate + NADP(+) = H(+) + NADPH + NH4(+) + oxaloacetate H2O + L-aspartate + NAD(+) = H(+) + NADH + NH4(+) + oxaloacetate Cofactor biosynthesis; NAD(+) biosynthesis; iminoaspartate from L-aspartate (dehydrogenase route): step 1/1. The iminoaspartate product is unstable in aqueous solution and can decompose to oxaloacetate and ammonia. Belongs to the L-aspartate dehydrogenase family.