Mammalian CerSs are orthologues of longevity-assurance genes, LAG1p and LAC1p identified in yeast (Guillas et al. 2001). The eukaryotes studied to date have been found to encode at least two CerSs, with humans expressing six – each generating CER with a defined acyl chain length (C18 to C26) (Pewzner-Jung et al. 2006; Levy & Futerman, 2010). Whilst little is known regarding structure-function relationships or regulation of CerS,, the ubiquitous Lag1 motif has been shown to be important for functionality (Spassieva et al. 2006), likely forming part of the active site.