title: Tracer studies with crude U-13C-lipid mixtures. Biosynthesis of the lipase inhibitor lipstatin.
abstract: The biosynthesis of the pancreatic lipase inhibitor lipstatin was investigated by fermentation experiments using cultures of Streptomyces toxytricini, which were supplied with soybean oil and a crude mixture of U-13C-lipids obtained from algal biomass cultured with 13CO2. Lipstatin was analyzed by one- and two-dimensional NMR spectroscopy. 13C total correlation spectroscopy and INADEQUATE experiments show that two fatty acid fragments containing 14 and 8 carbon atoms, respectively, are incorporated en bloc into lipstatin. The 14-carbon fragment is preferentially derived from the unsaturated fatty acid fraction, as shown by an experiment with hydrogenated U-13C-lipid mixture, which is conducive to labeling of the 8-carbon moiety but not of the 14-carbon moiety. The data indicate that the lipstatin molecule can be assembled by Claisen condensation of octanoyl-CoA with 3-hydroxy-delta5,8-tetradecanoyl-CoA obtained by beta oxidation of linoleic acid. The formation of lipstatin from acetate units by a polyketide-type pathway is ruled out conclusively by these data. The data show that surprisingly clear labeling patterns can be obtained in studies with crude, universally 13C-labeled precursor mixtures that are proffered together with a large excess of unlabeled material. One- and two-dimensional 13C total correlation spectroscopy analyses are suggested as elegant methods for the delineation of contiguously 13C-labeled biosynthetic blocks.
authors.affiliation: Department of Organic Chemistry and Biochemistry, Technical University of Munich, Federal Republic of Germany.
authors.forename: W
authors.initials: W
authors.lastname: Eisenreich
authors.forename: E
authors.initials: E
authors.lastname: Kupfer
authors.forename: W
authors.initials: W
authors.lastname: Weber
authors.forename: A
authors.initials: A
authors.lastname: Bacher
mesh_terms: D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007783:Lactones / Q000494:pharmacology*; D008049:Lipase / Q000037:antagonists & inhibitors*; D009682:Magnetic Resonance Spectroscopy; D000077403:Orlistat; D013302:Streptomyces
chemical_list: D004791:Enzyme Inhibitors; D007783:Lactones; D000077403:Orlistat; C054164:lipstatin; D008049:Lipase