Contribution of pentose phosphate pathway in developing castor bean endosperm

1971 ◽  
Vol 49 (2) ◽  
pp. 267-272 ◽  
Author(s):  
P. K. Agrawal ◽  
D. T. Canvin
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
Pentose Phosphate Pathway ◽  
Castor Bean ◽  
Lipid Synthesis ◽  
Experimental Period ◽  
Acid Synthesis ◽  
Pentose Phosphate ◽  
Fat Synthesis

Glucose-1-14C, glucose-6-14C, and glucose-U-14C were used to calculate the contribution of the PPP in developing castor bean endosperm tissues. Depending on the age of the seed 5–12% of the glucose-14C used was metabolized via the PPP and 88–95% via the EMP pathway. When lipid synthesis was rapid (20- to 28-day period) the PPP contribution was also at a maximum. During the 30- to 51-day period when lipid synthesis decreased so did the PPP contribution.With the data obtained from the PPP contribution the amount of NADPH produced during the experimental period was calculated. Also, the amount of fatty acids synthesized during that period was determined from glucose-U-14C data and thus the amount of NADPH required was calculated. Assuming that all the NADPH produced in the PPP was utilizable in fatty acid synthesis it was found that it was only sufficient to supply 50–75% of the reducing hydrogen required for fat synthesis. Therefore, the rest of the reducing hydrogen must come from some other sources, possibly NADH.

Glucose metabolism in the female rat adipocyte: lipid synthesis from glucose during pregnancy and progesterone treatment

1983 ◽  
Vol 97 (2) ◽  
pp. 207-212 ◽  
Author(s):  
M.-Th Sutter-Dub ◽  
A. Sfaxi ◽  
P. Strozza
Keyword(s):  
Fatty Acid ◽  
Glucose Metabolism ◽  
Fatty Acid Synthesis ◽  
Pentose Phosphate Pathway ◽  
Lipid Synthesis ◽  
Acid Synthesis ◽  
Pentose Phosphate ◽  
Ovariectomized Rats ◽  
Female Rat ◽  
Progesterone Treatment

Pregnancy and progesterone treatment of ovariectomized rats decrease glucose metabolism through the pentose-phosphate pathway in isolated female rat adipocytes. As demonstrated in previous studies, progesterone directly decreases [1-14C]glucose oxidation through the pentose-phosphate pathway and lipogenesis from [6-14C]glucose; the present study therefore compared glucose-induced lipid synthesis during pregnancy (10, 16 and 20 days of pregnancy) with the effect of progesterone treatment (5 mg/rat per day for 14 days) to shed more light on the role of this steroid in glucose metabolism during pregnancy. The inhibition of [6-14C]glucose incorporation into triacylglycerols in the progesterone-treated rats was comparable to that which occurs during late (20 days) and mid-pregnancy (16 days) but not during early pregnancy (10 days). The inhibition of fatty acid synthesis was more important as pregnancy advanced and was different from the decrease in fatty acid synthesis induced by progesterone treatment. The sensitivity to insulin was comparable in virgin, ovariectomized and progesterone-treated ovariectomized rats but not in pregnant rats. This implies that progesterone and insulin affect glucose-induced lipid synthesis by distinct processes and that the impaired glucose metabolism is characterized by a reduction in basal glucose utilization rather than by an impaired insulin response.

scholarly journals Interrelationship and control of glucose metabolism and lipogenesis in isolated fat-cells. Effect of the amount of glucose uptake on the rates of the pentose phosphate cycle and of fatty acid synthesis

1972 ◽  
Vol 128 (5) ◽  
pp. 1089-1096 ◽  
Author(s):  
H. Kather ◽  
M. Rivera ◽  
K. Brand
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Glucose Metabolism ◽  
Glucose Uptake ◽  
Fatty Acid Synthesis ◽  
Acid Synthesis ◽  
Pentose Phosphate ◽  
Fat Cells ◽  
Pentose Phosphate Cycle ◽  
Wide Range

In order to study the quantitative relationship between fatty acid synthesis and pentose phosphate-cycle activity under different hormonal and dietary conditions affecting the extent of glucose uptake, cells isolated from rat epididymal adipose tissue were incubated in bicarbonate buffer containing [U-14C]-, [1-14C]- or [6-14C]-glucose. From the amount of glucose taken up, the production of lactate and pyruvate, and the incorporation of 14C from differently labelled [14C]glucose into CO2, fatty acids and glyceride glycerol, the rates of glucose metabolism via different pathways and the extent of lipogenesis under various experimental conditions were determined. The contribution of the pentose phosphate-cycle to glucose metabolism under normal conditions was calculated to be 8%. Starvation and re-feeding, and the presence of insulin, caused an enhancement of glucose uptake, pentose phosphate-cycle activity and fatty acid synthesis. Plots of both pentose phosphate-cycle activity and fatty acid synthesis versus glucose uptake revealed that the extent of glucose uptake, over a wide range, determines the rates of fatty acid synthesis and glucose metabolism via the pentose phosphate cycle. A balance of formation and production of nicotinamide nucleotides in the cytoplasm was established. The total amount of cytoplasmic NADH and NADPH formed was only in slight excess over the hydrogen equivalents required for the synthesis of fatty acids, glyceride glycerol and lactate. Except in cells from starved animals, the pentose phosphate cycle was found to provide only about 60% of the NADPH required for fatty acid synthesis. The results are discussed with respect to an overall control of the different metabolic and biosynthetic reactions in the fat-cells by the amount of glucose transported into the cell.

Specific inhibition of iturin biosynthesis by cerulenin

1990 ◽  
Vol 36 (3) ◽  
pp. 164-168 ◽  
Author(s):  
Marie-Laure Hourdou ◽  
Françoise Besson ◽  
Georges Michel
Keyword(s):  
Fatty Acids ◽  
Protein Synthesis ◽  
Bacillus Subtilis ◽  
Fatty Acid ◽  
Amino Acid ◽  
Fatty Acid Synthesis ◽  
Lipid Synthesis ◽  
Acid Synthesis ◽  
Specific Inhibition ◽  
Malonyl Coa

Cerulenin, an inhibitor of fatty acid synthesis, inhibits the biosynthesis of iturin by Bacillus subtilis. With a cerulenin concentration of 2 μg/mL, 50% inhibition was achieved. At this concentration, cerulenin does not affect growth or total protein synthesis but does inhibit the incorporation of sodium [14C]acetate, [14C]myristic acid, and [14C]asparagine into iturin. Since cerulenin is known to block the condensation of malonyl-CoA subunits in the formation of fatty acids, the inhibition of iturin and β-amino acid syntheses by cerulenin is discussed in relation with lipid synthesis. Key words: iturin antibiotic, Bacillus subtilis, cerulenin, β-amino acid, lipid biosynthesis.

Fatty Acid Synthesis from Pyruvate in White Adipose Tissue: the Effect of Norepinephrine

1971 ◽  
Vol 49 (6) ◽  
pp. 736-741 ◽  
Author(s):  
M. L. Halperin
Keyword(s):  
Fatty Acids ◽  
Adipose Tissue ◽  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
Acid Synthesis ◽  
Pentose Phosphate ◽  
Epididymal Adipose Tissue ◽  
Phenazine Methosulfate ◽  
Fasted Rats ◽  
Lines Of Evidence

Pyruvate incorporation into fatty acids has been studied in epididymal adipose tissue taken from normal and 24-h-fasted rats. This rate was limited by the rate of cytoplasmic NADPH2 generation as suggested by three lines of evidence.(1) D-Glucose-12C increased pyruvate-U-14C incorporation into fatty acids threefold. This augmentation was independent of L-glycerol 3-phosphate concentrations as the level of this metabolite was not increased. Addition of lactate-U-14C to the pyruvate medium increased the tissue L-glycerol 3-phosphate levels but did not increase the rate of fatty acid synthesis.(2) Phenazine methosulfate (2 μM) inhibited pyruvate or pyruvate plus lactate (L/P = 3/1) conversion to fatty acids whilst stimulating fatty acid synthesis from glucose or lactate alone.(3) Norepinephrine stimulated pyruvate but not glucose or glucose plus pyruvate incorporation into fatty acids. This correlated with norepinephrine-induced glycogenosis and NADPH2 production in the pentose phosphate pathway. This was shown by increased 1-14CO2/6-14CO2 production from endogenously labelled glycogen and the absence of this effect in glycogen-depleted adipocytes (24-h-fasted rats).

scholarly journals The regulation of glyceride synthesis in isolated white-fat cells. The effects of palmitate and lipolytic agents

1972 ◽  
Vol 128 (5) ◽  
pp. 1057-1067 ◽  
Author(s):  
E. D Saggerson
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Free Fatty Acids ◽  
Fatty Acid Synthesis ◽  
Acid Synthesis ◽  
Fat Cells ◽  
Glyceride Synthesis ◽  
Glucose Incorporation ◽  
High Concentrations ◽  
Stimulation Of

1. 0.5mm-Palmitate stimulated incorporation of [U-14C]glucose into glyceride glycerol and fatty acids in normal fat cells in a manner dependent upon the glucose concentration. 2. In the presence of insulin the incorporation of 5mm-glucose into glyceride fatty acids was increased by concentrations of palmitate, adrenaline and 6-N-2′-O-dibutyryladenosine 3′:5′-cyclic monophosphate up to 0.5mm, 0.5μm and 0.5mm respectively. Higher concentrations of these agents produced progressive decreases in the rate of glucose incorporation into fatty acids. 3. The effects of palmitate and lipolytic agents upon the measured parameters of glucose utilization were similar, suggesting that the effects of lipolytic agents are mediated through increased concentrations of free fatty acids. 4. In fat cells from 24h-starved rats, maximal stimulation of glucose incorporation into fatty acids was achieved with 0.25mm-palmitate. Higher concentrations of palmitate were inhibitory. In fat cells from 72h-starved rats, palmitate only stimulated glucose incorporation into fatty acids at high concentrations of palmitate (1mm and above). 5. The ability of fat cells to incorporate glucose into glyceride glycerol in the presence of palmitate decreased with increasing periods of starvation. 6. It is suggested that low concentrations of free fatty acids stimulate fatty acid synthesis from glucose by increasing the utilization of ATP and cytoplasmic NADH for esterification of these free fatty acids. When esterification of free fatty acids does not keep pace with their provision, inhibition of fatty acid synthesis occurs. Provision of free fatty acids far in excess of the esterification capacity of the cells leads to uncoupling of oxidative phosphorylation and a secondary stimulation of fatty acid synthesis from glucose.

scholarly journals Modulation of lipid-synthesizing enzymes by insulin in differentiated ob17 adipose-like cells

1983 ◽  
Vol 214 (2) ◽  
pp. 443-449 ◽  
Author(s):  
P Grimaldi ◽  
C Forest ◽  
P Poli ◽  
R Negrel ◽  
G Ailhaud
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
Specific Activity ◽  
Fatty Acid Synthetase ◽  
Lipid Synthesis ◽  
Acid Synthesis ◽  
Acetate Incorporation ◽  
Long Term Effects ◽  
Response Curves ◽  
Glycerol 3 Phosphate Dehydrogenase

ob17 cells convert into adipose-like cells when maintained in the presence of physiological concentrations of insulin and tri-iodothyronine. After this conversion, insulin removal from differentiated ob17 cells gives within 24-48 h a large decrease in fatty acid synthetase, glycerol 3-phosphate dehydrogenase and acid:CoA ligase activities, as well as in the rate of fatty acid synthesis determined by [14C]acetate incorporation into lipids. All parameters are restored by insulin addition to initial values within 24-48 h. Dose-response curves of insulin on the restoration of glycerol 3-phosphate dehydrogenase activity and of fatty acid synthesis give half-maximally effective concentrations close to 1 nM, in agreement with the affinity for insulin of the insulin receptors previously characterized in these cells. Immunotitration experiments indicate that the changes in the specific activity of fatty acid synthetase are due to parallel changes in the cellular enzyme content. Therefore the ob17 cell line should be a useful model to study the long-term effects of insulin on the modulation of lipid synthesis in adipose cells.

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