Fatty acid synthesis in pea root plastids is inhibited by the action of long-chain acyl- coenzyme as on metabolite transporters.
The uptake in vitro of glucose (Glc)-6-phosphate (Glc-6-P) into plastids from the roots of 10- to 14-d-old pea (Pisum sativum L. cv Puget) plants was inhibited by oleoyl-coenzyme A (CoA) concentrations in the low micromolar range (1--2 microM). The IC(50) (the concentration of inhibitor that reduces enzyme activity by 50%) for the inhibition of Glc-6-P uptake was approximately 750 nM; inhibition was reversed by recombinant rapeseed (Brassica napus) acyl-CoA binding protein. In the presence of ATP (3 mM) and CoASH (coenzyme A; 0.3 mM), Glc-6-P uptake was inhibited by 60%, due to long-chain acyl-CoA synthesis, presumably from endogenous sources of fatty acids present in the preparations. Addition of oleoyl-CoA (1 microM) decreased carbon flux from Glc-6-P into the synthesis of starch and through the oxidative pentose phosphate (OPP) pathway by up to 73% and 40%, respectively. The incorporation of carbon from Glc-6-P into fatty acids was not detected under any conditions. Oleoyl-CoA inhibited the incorporation of acetate into fatty acids by 67%, a decrease similar to that when ATP was excluded from incubations. The oleoyl-CoA-dependent inhibition of fatty acid synthesis was attributable to a direct inhibition of the adenine nucleotide translocator by oleoyl-CoA, which indirectly reduced fatty acid synthesis by ATP deprivation. The Glc-6-P-dependent stimulation of acetate incorporation into fatty acids was reversed by the addition of oleoyl-CoA.
Fox
S R
SR
The Department of Brassica and Oilseeds Research, John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, United Kingdom.
Rawsthorne
S
S
Hills
M J
MJ
D000214:Acyl Coenzyme A / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000378:metabolism; D001692:Biological Transport; D001937:Brassica; D004734:Energy Metabolism; D005227:Fatty Acids / Q000096:biosynthesis*; D019298:Glucose-6-Phosphate / Q000378:metabolism; D006601:Hexoses / Q000378:metabolism; D066298:In Vitro Techniques; D018532:Pisum sativum / Q000187:drug effects / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism; D010969:Plastics / Q000378:metabolism*; D013213:Starch / Q000378:metabolism
D000214:Acyl Coenzyme A; D005227:Fatty Acids; D006601:Hexoses; D010969:Plastics; D019298:Glucose-6-Phosphate; D000255:Adenosine Triphosphate; D013213:Starch