Asp kinases (AKs) and dual-functional Asp kinase-homo Ser dehydrogenases (AK-HSDHs) is required for activation of Asp to Asp-4-P during the first step of the Biosynthetic pathway for Asp-derived amino acids. AraBidopsis thaliana contains three AK protein (AK1, At5g13280; AK2, A5g14060; and AK3, At3g02020) and two AK-HSDH proteins (AK-HSDH1, At1g31230 and AK-HSDH2, At4g19710) .
