SPT2

TgSPT2 is one of two serine palmitoyltransferases in Toxoplasma gondii that operate within the de novo ceramide biosynthesis pathway (PMID:35977499). Deletion of TgSPT2 perturbs the parasite sphingolipidome, producing a drastic reduction in ceramides and ceramide phosphoethanolamines while leaving sphingomyelins largely unaffected (PMID:35977499). Beyond this genetic and lipidomic characterization (PMID:35977499), no further mechanistic detail on TgSPT2 has been characterized in the available corpus.

1. 2022 Medium

   It was unknown which enzymes drive de novo ceramide synthesis in Toxoplasma; deletion of TgSPT2 established it as one of two serine palmitoyltransferases whose loss selectively collapses ceramide and ceramide phosphoethanolamine pools without affecting sphingomyelin.

   Evidence Gene knockout combined with mass spectrometry-based lipidomics and in vitro/in vivo phenotyping in T. gondii

   PMID:35977499

   Open questions at the time

   • The individual biochemical activity of TgSPT2 versus TgSPT1 was not resolved; fitness defects were primarily attributed to TgSPT1.
   • No structural model, substrate specificity, or reconstituted enzymatic assay for TgSPT2.
   • Subcellular localization and regulation of TgSPT2 not established.

• How TgSPT2 and TgSPT1 divide catalytic labor and whether TgSPT2 has a distinct substrate preference or regulatory role remains unresolved.
• No in vitro enzymatic characterization distinguishing TgSPT2 from TgSPT1.
• No interaction or complex data for TgSPT2.
• No localization data for TgSPT2.