title: Studies on the mechanism of 3-ketosphinganine synthetase.
abstract: The biosynthesis of sphinganine and 4-D-hydroxysphinganine was studied in rat liver microsomes and whole cells of yeast (Hansenula ciferri). It was shown in both cases that the condensation of [2,3,3-2H3]serine and palmitic acid yielded long chain bases containing only two deuterium atoms, both of which were located on the terminal (C-1) carbon atom by combined gas-liquid chromatography/mass spectrometry. When the reaction with the liver microsomal system was carried out in 2H2O with the protium species of serine, the sphinganine contained a deuterium atom on C-2. These results suggest that the synthesis of 3-ketosphinganine involves the replacement of the alpha-hydrogen atom and the carboxyl group of serine by a proton from the medium and a palmitoyl group, rather than a previously proposed mechanism in which the alpha-hydrogen of serine is retained. Some stereochemical requirements of 3-ketosphinganine synthetase are discussed.
mesh_terms: D000818:Animals; D001203:Ascomycota / Q000201:enzymology*; D019735:Carbon-Carbon Ligases; D008025:Ligases / Q000378:metabolism*; D008862:Microsomes, Liver / Q000201:enzymology*; D010169:Palmitic Acids / Q000378:metabolism; D010843:Pichia / Q000201:enzymology*; D051381:Rats; D012694:Serine / Q000378:metabolism; D013045:Species Specificity; D013110:Sphingosine / Q000031:analogs & derivatives
chemical_list: D010169:Palmitic Acids; D012694:Serine; D008025:Ligases; C023945:3-ketosphinganine synthetase; D019735:Carbon-Carbon Ligases; D013110:Sphingosine