Orm proteins control ceramide synthesis and endocytosis via LCB-mediated Ypk1 regulation.

Sphingolipids (SPLs) are major components of cell membranes with significant functions. Their production is a highly-regulated multi-step process with the formation of two major intermediates, long chain bases (LCBs) and ceramides. Homologous Orm proteins in both yeast and mammals negatively regulate LCB production by inhibiting serine palmitoyltransferase (SPT), the first enzyme in SPL de novo synthesis.