The Effects of Inhibitors on the Biosynthesis of the Long Chain Lipids with even Carbon Numbers in Barley Spike Epicuticular Wax

Jørn Dalgaard Mikkelsen

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The effects of inhibitors on the incorporation of label from [2-14C]-acetate into the epicuticular wax classes witheven carbon numbers have been determined. They include the free fatty acids, the primary alcohols, thealdehydes, the ester acids and a newly identified wax class on barley spikes, the short chain esters. Dithiothreitol,which has no effect on β-diketone synthesis, inhibits decarboxylation of very long fatty acyl chains which areprecursors of the alkanes. Mercaptoethanol, which greatly stimulates wax synthesis at low concentrations andhas no effect on 13-diketone synthesis, blocks further elongation of fatty acyl precursors having 20 carbons athigher concentrations. A relatively small inhibition of decarboxylation was also observed with mercaptoethanol.Arsenite, which inhibits 13-diketone synthesis presumably by blocking the entrance of C16 precursors into the 13-diketone elongation mechanism, was also found to prevent the C20-C22 elongation step in the sequence leading tothe alkanes. Cyanide, which blocks 13-diketone synthesis by an unknown mechanism, greatly stimulated synthesisof the other wax classes. At higher concentrations a block in the elongation sequence leading to the alkanes wasalso apparent between C26-C28. These results are incorporated into a composite figure illustrating the biosyntheticrelationships among the wax classes. All identified chemical and genetic blocks have been included. The conclusionis reached that at least three elongation systems must be involved.
Original languageEnglish
JournalCarlsberg Research Communications
Pages (from-to)15-35
Publication statusPublished - 1978
Externally publishedYes


  • Fatty acids
  • Primary alcohols
  • Aldehydes
  • Esters
  • 14C-acetate
  • Cyanide
  • Arsenite
  • Dithiothreitol
  • Mercaptoethanol

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