SPTL-1 is a component of serine palmitoyltransferase (SPT), a crucial enzyme complex catalyzing the initial and rate-limiting step in sphingolipid biosynthesis. This step involves the condensation of an acyl-CoA species and L-serine. The catalytic core of SPT is a heterodimer; either SPTL1/SPTL2 or SPTL1/SPTL3. SPTL-1 is essential for establishing apicobasal polarity and the proper development of the gut lumen.