[1] Serine palmitoyltransferase

The committed step in de novo sphingolipid synthesis begins with the condensation of L-serine and palmitoyl-CoA to produce a C18 carbon unit, D-3-ketosphinganine, or 3-ketodihydrosphingosine (D-2-amino-l-hydroxyoctadecan-3-one). This reaction, catalyzed by serine palmitoyltransferase (SPT), EC 2.3.1.50, also called “3-ketosphinganine synthase,” was first demonstrated in cell-free extracts made from the yeast Hansenula ciferrii. Shortly thereafter, its existence was shown in extracts prepared from rat liver and mouse brain. Snell and co-workers recognized that the enzyme requires pyridoxal phosphate for activity. The assay of SPT activity is based on the conversion of water-soluble [3H] serine to the chloroform-soluble product, 3-ketosphinganine. The most widely used format of this assay, Protocol I, is based on the original work of Williams et al. and on recent modifications, is Protocol II is a modified format that employs an alternative extraction procedure developed by Wells and Lester (unpublished results) and is used routinely for assay of SPT activity in S. cerevisiae.