Serine C-palmitoyltransferase

In enzymology, a serine C-palmitoyltransferase is an enzyme that catalyzes the chemical reaction:


 * palmitoyl-CoA + L-serine $$\rightleftharpoons$$ CoA + 3-dehydro-D-sphinganine + CO2

Thus, the two substrates of this enzyme are palmitoyl-CoA and L-serine, whereas its 3 products are CoA, 3-dehydro-D-sphinganine, and CO2. This reaction is a key step in the biosynthesis of sphingosine which is a precursor of many other sphingolipids.

This enzyme belongs to the family of transferases, specifically those acyltransferases transferring groups other than aminoacyl groups. The systematic name of this enzyme class is palmitoyl-CoA:L-serine C-palmitoyltransferase (decarboxylating). Other names in common use include serine palmitoyltransferase, SPT, 3-oxosphinganine synthetase, and acyl-CoA:serine C-2 acyltransferase decarboxylating. This enzyme participates in sphingolipid metabolism. It employs one cofactor, pyridoxal phosphate.

Species distribution
This enzyme is expressed in a large number of species from bacteria to humans. The bacterial enzyme is a water soluble homodimer whereas in eukaryotes the enzyme is a heterodimer which is anchored to the endoplasmic reticulum. Humans and other mammals express three paralogous subunits SPTLC1, SPTLC2, and SPTLC3. It was originally proposed that the functional human enzyme is a heterodimer between a SPTLC1 subunit and a second subunit which is either SPTLC2 or SPTLC3. However more recent data suggest that the enzyme may exist as a larger complex, possibly a octamer, comprising all three subunits.

Structural studies
As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes and.