Serine palmitoyltransferase (SPT). The heterodimer formed with LCB2 constitutes the catalytic core. Involved in the regulation of the programmed cell death (PCD) signaling pathway. Plays an important role during male gametogenesis and embryogenesis. H(+) + hexadecanoyl-CoA + L-serine = 3-oxosphinganine + CO2 + CoA Lipid metabolism; sphingolipid metabolism. Heterodimer with LCB2 (LCB2a or LCB2b). Component of the serine palmitoyltransferase (SPT) complex, composed of LCB1 and LCB2 (LCB2a or LCB2b). Ubiquitous. Defective Embryo and pollen lethality. RNAi mutants display plant size reduction, altered leaf morphology and increases in relative amounts of saturated sphingolipid long-chain bases. The fbr11-1 mutant is incapable of initiating programmed cell death (PCD) after induction by fumonisin B1 (FB1), a specific inhibitor of ceramide synthase. Belongs to the class-II pyridoxal-phosphate-dependent aminotransferase family.