Fatty acid and lipoic acid biosynthesis in higher plant mitochondria.
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.
Gueguen
V
V
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.
Macherel
D
D
Jaquinod
M
M
Douce
R
R
Bourguignon
J
J
D051080:Acyl-Carrier Protein S-Malonyltransferase; D000217:Acyltransferases / Q000378:metabolism*; D001426:Bacterial Proteins; D002250:Carbon Radioisotopes; D002851:Chromatography, High Pressure Liquid; D003066:Coenzyme A Ligases / Q000378:metabolism; D005227:Fatty Acids / Q000096:biosynthesis*; D008314:Malonates / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism*; D018532:Pisum sativum / Q000201:enzymology / Q000378:metabolism*; D018515:Plant Leaves / Q000201:enzymology / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D008063:Thioctic Acid / Q000096:biosynthesis*
D001426:Bacterial Proteins; D002250:Carbon Radioisotopes; D005227:Fatty Acids; D008314:Malonates; D008063:Thioctic Acid; C030290:malonic acid; D000217:Acyltransferases; D051080:Acyl-Carrier Protein S-Malonyltransferase; D003066:Coenzyme A Ligases; C021533:malonyl-CoA synthetase