Cellular component

SPOTS complex, SPT, serine C-palmitoyltransferase complex, serine palmitoyltransferase, Orm1/2, Tsc3 and Sac1 complex

A protein complex that catalyses the condensation of L-serine with palmitoyl-CoA to form 3-ketosphinganine, the sphingoid base which is the starting point for all sphingolipids. In bacteria the enzyme is a cytoplasmic homodimer, whereas in eukaryotes the enzyme is a multiprotein complex localised to the endoplasmic reticulum. The eukaryotic complex consists of catalytic components (SPTLC1, SPTLC2 and SPTLC3 in humans; LCB1 and LCB2 in S. cerevisiae) and regulatory components, which include activators (SPTSSA/SPTSSB in humans, TSC3 in S. cerevisiae) and negative regulators (ORMDL1/ORMDL2/ORMDL3 in humans, ORM1/2 in S. cerevisiae ).