scholarly journals Inhibition by long-chain acyl-CoAs of glucose 6-phosphate metabolism in plastids isolated from developing embryos of oilseed rape (Brassica napus L.)

2000 ◽  
Vol 348 (1) ◽  
pp. 145-150 ◽  
Author(s):  
Philip E. JOHNSON ◽  
Simon R. FOX ◽  
Matthew J. HILLS ◽  
Stephen RAWSTHORNE
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
De Novo ◽  
Starch Synthesis ◽  
Acid Synthesis ◽  
Pentose Phosphate ◽  
Pyruvate Metabolism ◽  
Brassica Napus L ◽  
Chain Acyl ◽  
Long Chain

The effects of long-chain acyl-CoA (lcACoA) esters (both added exogenously and synthesized de novo) and acyl-CoA binding protein (ACBP) on plastidial glucose 6-phosphate (Glc6P) and pyruvate metabolism were examined using isolated plastids. The binding of lcACoA esters by ACBP stimulated the utilization of Glc6P for fatty acid synthesis, starch synthesis and reductant supply via the oxidative pentose phosphate (OPP) pathway. Stimulation occurred at low (1-10 μM) concentrations of ACBP. Pyruvate-dependent fatty acid synthesis was not directly affected by ACBP. However, addition of ACBP did increase the Glc6P-dependent stimulation of pyruvate utilization mediated through the OPP pathway. On the basis of these experiments, we conclude that lcACoA esters may inhibit Glc6P uptake into plastids, and that this inhibition is relieved by ACBP. We also suggest that utilization of other substrates for fatty acid synthesis may be affected by lcACoA/ACBP via their effects on the OPP pathway.

scholarly journals Inhibition of the glucose-6-phosphate transporter in oilseed rape (Brassica napus L.) plastids by acyl-CoA thioesters reduces fatty acid synthesis

2000 ◽  
Vol 352 (2) ◽  
pp. 525-532 ◽  
Author(s):  
Simon R. FOX ◽  
Lionel M. HILL ◽  
Stephen RAWSTHORNE ◽  
Matthew J. HILLS
Keyword(s):  
Fatty Acid ◽  
Brassica Napus ◽  
Oilseed Rape ◽  
Acid Synthesis ◽  
Brassica Napus L ◽  
Coa Ligase ◽  
Chain Acyl ◽  
Coa Thioesters ◽  
Long Chain

Addition of oleoyl-CoA (1µM), or other acyl-CoA thioesters with a chain length of C16 or greater, to oilseed rape plastids (Brassica napus L.) inhibited the rate of D-glucose 6-phosphate (Glc6P) uptake by 70% after 2min. The IC50 value for oleoyl-CoA inhibition of the transporter was approx. 0.2–0.3µM. Inhibition was alleviated by the addition of acyl-CoA binding protein (ACBP) or BSA at slightly higher concentrations. Oleic acid (5–25µM), Tween 40 (10µM), Triton-X 100 (10µM) and palmitoylcarnitine (5µM) had no effect on Glc6P uptake. The uptake of [1-14C]Glc6P occurred in exchange for Pi, 3-phosphoglycerate or Glc6P at a typical rate of 30nmol Glc6P/min per unit of glyceraldehyde-3-phosphate dehydrogenase (NADP+). The Km(app) of the Glc6P transporter for Glc6P was 100µM. Neither CoA (0.3mM) nor ATP (3mM) inhibited Glc6P uptake, but the transporter was inhibited by 72% when ATP and CoA were added together. This inhibition was attributable to the synthesis of acyl-CoA thioesters, predominantly oleoyl-CoA and palmitoyl-CoA, by long-chain fatty acid-CoA ligase (EC 6.2.1.3) from endogenous fatty acids in the plastid preparations. Acyl-CoA thioesters did not inhibit the uptake of [2-14C]pyruvate or D-[1-14C]glucose into plastids. In vivo quantities of oleoyl-CoA and other long-chain acyl-CoA thioesters were lower than those for ACBP in early cotyledonary embryos, 0.7±0.2pmol/embryo and 2.2±0.2pmol/embryo respectively, but in late cotyledonary embryos quantities of long-chain acyl-CoA thioesters were greater than ACBP, 3±0.4pmol/embryo and 1.9±0.2pmol/embryo respectively.

scholarly journals A yeast acetyl coenzyme A carboxylase mutant links very-long-chain fatty acid synthesis to the structure and function of the nuclear membrane-pore complex.

1996 ◽  
Vol 16 (12) ◽  
pp. 7161-7172 ◽  
Author(s):  
R Schneiter ◽  
M Hitomi ◽  
A S Ivessa ◽  
E V Fasch ◽  
S D Kohlwein ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
De Novo ◽  
Acid Synthesis ◽  
Chain Fatty Acid ◽  
Intermembrane Space ◽  
Long Chain Fatty Acid ◽  
Acetyl Coenzyme A ◽  
Long Chain

The conditional mRNA transport mutant of Saccharomyces cerevisiae, acc1-7-1 (mtr7-1), displays a unique alteration of the nuclear envelope. Unlike nucleoporin mutants and other RNA transport mutants, the intermembrane space expands, protuberances extend from the inner membrane into the intermembrane space, and vesicles accumulate in the intermembrane space. MTR7 is the same gene as ACC1, encoding acetyl coenzyme A (CoA) carboxylase (Acc1p), the rate-limiting enzyme of de novo fatty acid synthesis. Genetic and biochemical analyses of fatty acid synthesis mutants and acc1-7-1 indicate that the continued synthesis of malonyl-CoA, the enzymatic product of acetyl-CoA carboxylase, is required for an essential pathway which is independent from de novo synthesis of fatty acids. We provide evidence that synthesis of very-long-chain fatty acids (C26 atoms) is inhibited in acc1-7-1, suggesting that very-long-chain fatty acid synthesis is required to maintain a functional nuclear envelope.

scholarly journals Synthesis of fatty acids in the perfused mouse liver

1974 ◽  
Vol 142 (3) ◽  
pp. 611-618 ◽  
Author(s):  
D. Michael W. Salmon ◽  
Neil L. Bowen ◽  
Douglas A. Hems
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
De Novo ◽  
Saturated Fatty Acids ◽  
Carbon Sources ◽  
Acid Synthesis ◽  
Hepatic Glycogen ◽  
Total Rate ◽  
Glucose Carbon

1. Fatty acid synthesis de novo was measured in the perfused liver of fed mice. 2. The total rate, measured by the incorporation into fatty acid of3H from3H2O (1–7μmol of fatty acid/h per g of fresh liver), resembled the rate found in the liver of intact mice. 3. Perfusions with l-[U-14C]lactic acid and [U-14C]glucose showed that circulating glucose at concentrations less than about 17mm was not a major carbon source for newly synthesized fatty acid, whereas lactate (10mm) markedly stimulated fatty acid synthesis, and contributed extensive carbon to lipogenesis. 4. The identification of 50% of the carbon converted into newly synthesized fatty acid lends further credibility to the use of3H2O to measure hepatic fatty acid synthesis. 5. The total rate of fatty acid synthesis, and the contribution of glucose carbon to lipogenesis, were directly proportional to the initial hepatic glycogen concentration. 6. The proportion of total newly synthesized lipid that was released into the perfusion medium was 12–16%. 7. The major products of lipogenesis were saturated fatty acids in triglyceride and phospholipid. 8. The rate of cholesterol synthesis, also measured with3H2O, expressed as acetyl residues consumed, was about one-fourth of the basal rate of fatty acid synthesis. 9. These results are discussed in terms of the carbon sources of hepatic newly synthesized fatty acids, and the effect of glucose, glycogen and lactate in stimulating lipogenesis, independently of their role as precursors.

scholarly journals A low-protein, high-carbohydrate diet increases de novo fatty acid synthesis from glycerol and glycerokinase content in the liver of growing rats

2013 ◽  
Vol 33 (6) ◽  
pp. 494-502 ◽  
Author(s):  
Andreza Lúcia Menezes ◽  
Mayara Peron Pereira ◽  
Samyra Lopes Buzelle ◽  
Maísa Pavani dos Santos ◽  
Suélem Aparecida de França ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
De Novo ◽  
Acid Synthesis ◽  
High Carbohydrate Diet ◽  
Carbohydrate Diet ◽  
High Carbohydrate ◽  
Growing Rats ◽  
Low Protein
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