KBL_like; this family belongs to the pyridoxal phosphate (PLP)-dependent aspartate aminotransferase superfamily (fold I). The major groups in this CD corresponds to serine palmitoyltransferase (SPT), 5-aminolevulinate synthase (ALAS), 8-amino-7-oxononanoate synthase (AONS), and 2-amino-3-ketobutyrate CoA ligase (KBL). SPT is responsible for the condensation of L-serine with palmitoyl-CoA to produce 3-ketodihydrospingosine, the reaction of the first step in sphingolipid biosynthesis. ALAS is involved in heme biosynthesis; it catalyzes the synthesis of 5-aminolevulinic acid from glycine and succinyl-coenzyme A. AONS catalyses the decarboxylative condensation of l-alanine and pimeloyl-CoA in the first committed step of biotin biosynthesis. KBL catalyzes the second reaction step of the metabolic degradation pathway for threonine converting 2-amino-3-ketobutyrate, to glycine and acetyl-CoA. The members of this CD are widely found in all three forms of life.