Abstract：
:Serine palmitoyltransferase (EC 2.3.1.50) catalyzes the condensation of L-serine and palmitoyl-CoA to yield 3-ketosphinganine in the first unique reaction of long-chain (sphingoid) base biosynthesis. The kinetic effects of changing the extracellular concentrations of the precursors for this pathway were studied with LM cells by following the incorporation of L-[3-14C]serine into the long-chain base (i.e., sphinganine and sphingenine) backbones of complex sphingolipids. [14C]Serine was taken up by the cells and rapidly reached steady-state concentrations similar to those of the medium. From the cellular [14C]serine concentrations and specific activities, the apparent Vmax [14 pmol min-1 (10(6) cells)-1] and Km (0.23 mM) values for long-chain base synthesis were determined and found to be essentially identical with those for serine palmitoyltransferase assayed in vitro [i.e., 13 pmol min-1 (10(6) cells)-1 and 0.27 mM, respectively]. The other precursor, palmitic acid, was also taken up rapidly and increased long-chain base biosynthesis in a concentration-dependent manner. This effect was limited to palmitic acid and matched the known specificity of serine palmitoyltransferase for saturated fatty acyl-CoA's of 16 +/- 1 carbon atoms. These studies delineate the influence of extracellular precursors on the formation of the sphingolipid backbone and suggest that the kinetic properties of serine palmitoyltransferase govern this behavior of long-chain base synthesis in intact cells.
journal_name
Biochemistryjournal_title
Biochemistryauthors
Merrill AH Jr,Wang E,Mullins REdoi
10.1021/bi00401a051subject
Has Abstractpub_date
1988-01-12 00:00:00pages
340-5issue
1eissn
0006-2960issn
1520-4995journal_volume
27pub_type
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