title: Use of 13C in biosynthetic studies. The labelling pattern in tenellin enriched from isotope-labelled acetate, methionine, and phenylalanine.
abstract: The biogenetic origin of the carbon atoms in tenellin has been established by adding 13C-enriched compounds to cultures of Beauveria bassiana, and determining the isotopic distribution in the metabolite by 13C nuclear magnetic resonance spectrometry. Tenellin is formed by condensation of an acetate-derived polyketide chain with a phenylpropanoid unit that may be phenylalanine. Alternate carbon atoms of the polyketide chain were labelled with sodium [1(-13C)]- and [2-(13C]-acetate; sodium [1,2-(13C)]acetate was incorporated as intact two-carbon units, the presence of which in tenellin was apparent from coupling between adjacent 13C-enriched carbons. Substituent methyl groups of the polyketide-derived alkenyl chain were labelled with L-[Me-13C]methionine. The labelling patterns from DL-[carboxy-13C]phenylalanine and DL-[alpha-13C]phenylalanine indicated a rearrangement of the propanoid component at some stage in the synthesis. The mass spectrum of tenellin from cultures administered L-[15N]phenylalanine showed isotopic enrichment similar to that obtained with 13C- or 14C-labelled phenylalanine. During incorporation of L-[carboxy-14C, beta-3H]phenylalanine 96% of the tritium label was lost, discounting the possibility of a 1,2-hydride shift during biosynthesis of the metabolite.
mesh_terms: D000085:Acetates / Q000378:metabolism*; D002247:Carbon Isotopes; D005658:Fungi; D007553:Isotope Labeling; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008433:Mathematics; D008715:Methionine / Q000378:metabolism*; D003904:Mitosporic Fungi / Q000378:metabolism*; D010649:Phenylalanine / Q000378:metabolism*; D010860:Pigments, Biological / Q000096:biosynthesis* / Q000302:isolation & purification; D011728:Pyridones / Q000096:biosynthesis*
chemical_list: D000085:Acetates; D002247:Carbon Isotopes; D010860:Pigments, Biological; D011728:Pyridones; D010649:Phenylalanine; C015528:tenellin; D008715:Methionine