Fatty acid and lipoic acid biosynthesis in higher plant mitochondria |
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Authors: | Gueguen V Macherel D Jaquinod M Douce R Bourguignon J |
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Institution: | Laboratoire de Physiologie Cellulaire Végétale, URA 576, CEA/CNRS/Université Joseph Fourier, Département de Biologie Moléculaire et Structurale, CEA-GRENOBLE, 17 Rue des Martyrs, 38054 Grenoble Cedex 9, France. |
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Abstract: | Fatty acid and lipoic acid biosynthesis were investigated in plant mitochondria. Although the mitochondria lack acetyl-CoA carboxylase, our experiments reveal that they contain the enzymatic equipment necessary to transform malonate into the two main building units for fatty acid synthesis: malonyl- and acetyl-acyl carrier protein (ACP). We demonstrated, by a new method based on a complementary use of high performance liquid chromatography and mass spectrometry, that the soluble mitochondrial fatty-acid synthase produces mainly three predominant acyl-ACPs as follows: octanoyl(C8)-, hexadecanoyl(C16)-, and octadecanoyl(C18)-ACP. Octanoate production is of primary interest since it has been postulated long ago to be a precursor of lipoic acid. By using a recombinant H apoprotein mutant as a potential acceptor for newly synthesized lipoic acid, we were able to detect limited amounts of lipoylated H protein in the presence of malonate, several sulfur donors, and cofactors. Finally, we present a scheme outlining the new biochemical pathway of fatty acid and lipoic acid synthesis in plant mitochondria. |
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