The SPTLC3 subunit of serine palmitoyltransferase generates short chain sphingoid bases.
The enzyme serine palmitoyltransferase (SPT) catalyzes the rate-limiting step in the de novo synthesis of sphingolipids. Previously the mammalian SPT was described as a heterodimer composed of two subunits, SPTLC1 and SPTLC2. Recently we identified a novel third SPT subunit (SPTLC3). SPTLC3 shows about 68% identity to SPTLC2 and also includes a pyridoxal phosphate consensus motif. Here we report that the overexpression of SPTLC3 in HEK293 cells leads to the formation of two new sphingoid base metabolites, namely C(16)-sphinganine and C(16)-sphingosine. SPTLC3-expressing cells have higher in vitro SPT activities with lauryl- and myristoyl-CoA than SPTLC2-expressing cells, and SPTLC3 mRNA expression levels correlate closely with the C(16)-sphinganine synthesis rates in various human and murine cell lines. Approximately 15% of the total sphingolipids in human plasma contain a C(16) backbone and are found in the high density and low density but not the very low density lipoprotein fraction. In conclusion, we show that the SPTLC3 subunit generates C(16)-sphingoid bases and that sphingolipids with a C(16) backbone constitute a significant proportion of human plasma sphingolipids.
Hornemann
Thorsten
T
Institute for Clinical Chemistry, University Hospital Zurich, CH-8091 Zurich, Switzerland. thorsten.hornemann@usz.ch
Penno
Anke
A
Rütti
Markus F
MF
Ernst
Daniela
D
Kivrak-Pfiffner
Fatma
F
Rohrer
Lucia
L
von Eckardstein
Arnold
A
D002384:Catalysis / Q000187:drug effects; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D015870:Gene Expression; D006801:Humans; D007700:Kinetics; D013058:Mass Spectrometry; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012694:Serine / Q000494:pharmacology; D051102:Serine C-Palmitoyltransferase / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D013107:Sphingolipids / Q000097:blood / Q000737:chemistry / Q000378:metabolism*; D013110:Sphingosine / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism
D012333:RNA, Messenger; D013107:Sphingolipids; D012694:Serine; C521151:SPTLC3 protein, human; D051102:Serine C-Palmitoyltransferase; D013110:Sphingosine; C005682:safingol