Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:6.4.1.2 (acetyl-CoA carboxylase)
 2,876 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cellular content of acetyl-CoA carboxylase [acetyl-CoA:carbon-dioxide ligase (ADP-forming), EC 6.4.1.2] in Saccharomyces cerevisiae is reduced by the addition of long-chain fatty acids to the culture medium. Mutant strains of S. cerevisiae defective in acyl-CoA synthetase [acid:CoA ligase (AMP-forming), EC 6.2.1.3] were isolated and used to determine whether fatty acid itself or a metabolite of fatty acid is more directly responsible for the repression of acetyl-CoA carboxylase. Cells of the mutant strains were capable of incorporating fatty acid to an extent comparable to that observed with the wild-type strain, but they accumulated markedly more of the incorporated fatty acid in the nonesterified form than did the wild-type cells. The level of acetyl-CoA carboxylase activity in the mutants, in contrast to that in the wild-type strain, was hardly affected by the addition of fatty acids to the medium. These results indicate that the activation of exogenous fatty acid is required for the repression of acetyl-CoA carboxylase, supporting the view that the repressive effect is mediated by some compound metabolically derived from fatty acid.
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PMID:Evidence that acyl coenzyme A synthetase activity is required for repression of yeast acetyl coenzyme A carboxylase by exogenous fatty acids. 0 54

The long-term regulation of fatty acid synthetase and acetyl-CoA carboxylase and of fatty acid and sterol synthesis was studied in C-6 glial cells in culture. When theophylline (10(-3) M) was added to the culture medium of these cells, rates of lipid synthesis from acetate and activities of synthetase and carboxylase became distinctly lower than in cells that were untreated. This effect appeared after approximately 12 h, and after 48 h enzymatic activities were reduced approx. 2-fold and rates of lipid synthesis from acetate 3- to 4-fold. The likelihood that the decrease in fatty acid synthesis from acetate was caused by the decrease in activities of fatty acid synthetase and acetyl-CoA carboxylase was established by several observations. These indicated that the locus of the effect probably did not reside at the level of acetate uptake into the cell, alterations in acetate pool sizes or conversion of acetate to acetyl-CoA. Moreover, de novo fatty acid synthesis was found to be the predominant pathway in these glial cells, whether treated with theophylline or not. The mechanism of the effect of theophylline on fatty acid synthetase was shown by immunochemical techniques to involve an alteration in content of enzyme rather than in catalytic efficiency. The change in content of fatty acid synthetase was shown by isotopic-immunochemical experiments to involve a decrease in synthesis of the enzyme. The mechanism whereby theophylline leads to a decrease in lipogenesis and in the synthesis of fatty acid synthetase may not be mediated entirely by inhibition of phosphodiesterase and an increase in cyclic AMP levels, because dibutyryl cyclic AMP (10(-3) M) only partially reproduced the effect.
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PMID:Long-term regulation by theophylline of fatty acid synthetase, acetyl-CoA carboxylase and lipid synthesis in cultured glial cells. 0 98

Evidence is presented that rat liver microsomal fatty acid chain elongation synthesis and desaturation, as well as acetyl-CoA carboxylase and fatty acid synthetase, are strongly influenced by thyroid hormone level. Conversely, the fatty acid chain elongation system in mitochondria, unlike the oxidative capacity of palmitate, NADH, succinate and malate, does not seem significantly affected by the thyrotoxic state. In triiodothyronine-induced or thyroxine-induced hyperthyroidism, rat liver acetyl-CoA carboxylase, fatty acid synthetase and microsomal chain elongation and desaturation reactions are not greatly affected after the first 10 days of treatment, while after longer intervals a respective increase in these activities is shown of up to 87, 116 and 65% after 22 days. In propylthiouracil-induced hypothyroidism, all the above synthetic activities are strongly reduced immediately after three days of drug administration and diminished no further following longer periods. Although the pattern of synthesized fatty acids in the thyrotoxic state is similar to that obtained from normal subcellular rat fractions, the esterification process of fatty acids in microsomal lipids appears to be slightly inhibited in hypothyroid rats and increased following triiodothyronine or thyroxine administration. Finally, a reduction in the hepatic cyclic AMP level of about 41% is reported after 19 days of triiodothyronine-administration to rats. On the basis of the observed insensitivity of the mitochondrial fatty acid chain elongation system to the thyrotoxic state, a tentative interpretation of its role in the hepatic cell is postulated.
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PMID:Effect of thyroid hormones on microsomal fatty acid chain elongation synthesis in rat liver. 1 55

It has been suggested that the carbohydrate-rich diet of chicks after hatching is responsible for the emergence of hepatic enzymes involved in lipogenesis; the injection of glucose to newly hatched chicks gives rise to an appreciable elvation on the activities of acetyl coenzyme A carboxylase and fatty acid synthetase. The present study shows that during the first hours after hatching, there is a natural elevation of glycemia which parallels the increase in acetyl coenzyme A carboxylase activity. However, the administration of hormones which alter the blood glucose levels considerably (insulin, tolbutamide, glucagon and hydrocortisone) did not influence the enzyme activity. The administration of thyroxine, estradiol and cyclic AMP, was also without effect. These results do not support the theory that the increased amount of blood glucose is the natural effector of the induction acetyl coenzyme A carboxylase. They also show that different lipogenic enzymes are not regulated via the same 'operon' since thyroxine or glucagon which alter the level of some enzymes on this pathway did not modify that of the acetyl coenzyme A carboxylase.
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PMID:Development of hepatic acetyl coenzyme A carboxylase in hormone-treated chicks. 1 45

The effects of citrate and cyclic AMP on the rate and degree of phosphorylation and inactivation of rat liver acetyl-CoA carboxylase were examined. High citrate concentrations (10 to 20 mM), which are generally used to stabilize and activate the enzyme, inhibit phosphorylation and inactivation of carboxylase. At lower concentrations of citrate, the rate and degree of phosphorylation are increased. Furthermore, phosphorylation and enzyme inactivation are affected by cyclic AMP under these conditions. At high citrate concentrations, cyclic AMP has little or no effect on inactivation and phosphorylation of acetyl-CoA carboxylase. Phosphorlation and inactivation of carboxylase is accompanied by depolymerization of the polymeric form of the enzyme into intermediate and protomeric forms. Depolymerization of carboxylase requires the transfer of the gamma-phosphate group from ATP to carboxylase. Inactivation occurs in the absence of CO2, which indicates that phosphorylation of the enzyme is the cause of inactivation and depolymerization, i.e. carboxylation of the enzyme is not responsible for inactivation of the enzyme.
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PMID:Regulation of rat liver acetyl-CoA carboxylase. Stimulation of phosphorylation and subsequent inactivation of liver acetyl-CoA carboxylase by cyclic 3':5'-monophosphate and effect on the structure of the enzyme. 3 Jul 74

A hormonally induced change in the covalent phosphorylation state of several enzymes is generally regarded as an important mechanism for hormonal modulation of enzyme activity. We have previously demonstrated that epinephrine stimulates the phosphorylation of a peptide of Mr = 220,000 in adipocytes. Incubation of 32P-labeled cytosolic proteins from adipocytes and hepatocytes with antisera raised against homogeneous chicken and rat liver acetyl coenzyme A carboxylase results in the specific and complete precipitation of the same phosphopeptide. No other major phosphopeptide is specifically precipitated. In hepatocytes, glucagon stimulates the incorporation of 32P into this peptide associated with an inhibition of enzyme activity. These data, coupled with previous studies in adipocytes, suggest that cyclic AMP-dependent protein phosphorylation plays a major role in the regulation of acetyl-CoA carboxylase activity and of fatty acid biosynthesis in adipose tissue and liver.
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PMID:Glucagon regulation of protein phosphorylation. Identification of acetyl coenzyme A carboxylase as a substrate. 3 66

Mutant strains of Candida lipolytica defective in acyl-CoA synthetase II [acid:CoA ligase (AMP-forming), EC 6.2.1.3] have been isolated. The mutants fail to grow on fatty acid as a sole carbon source but are capable of incorporating exogenous fatty acid into cellular lipids. This observation, together with our previous finding that mutant strains defective in acyl-CoA synthetase I cannot incorporate exogenous fatty acid into cellular lipids but are able to degrade fatty acid via beta-oxidation, indicates the presence of two functionally distinct long-chain acyl-CoA pools in the cell--i.e., one for lipid synthesis and the other for beta-oxidation. Unlike the wild-type and the revertant strains as well as the mutants lacking acyl-CoA synthetase II, the mutants defective in acyl-CoA synthetase I do not exhibit the repression of acetyl-CoA carboxylase [acetyl-CoA:carbon-dioxide ligase (ADP-forming), EC 6.4.1.2] by exogenous fatty acid. Measurement of the two long-chain acyl-CoA pools with the aid of appropriate mutant strains has indicated that the long-chain acyl-CoA to be utilized for lipid synthesis, but not that to be degraded via beta-oxidation, is involved in the repression of acetyl-CoA carboxylase.
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PMID:Involvement of long-chain acyl coenzyme A for lipid synthesis in repression of acetyl-coenzyme A carboxylase in Candida lipolytica. 4 Dec 42

Chick liver cell monolayers synthesize fatty acids at in vivo rates and are responsive to insulin and glucagon. High rates of fatty acid synthesis are maintained with insulin present and lost slowly without insulin. Glucagon or 3',5'-cyclic AMP cause immediate cessation of fatty acid synthesis. The site of inhibition appears to be cytoplasmic acetyl-CoA carboxylase which catalyzes the first committed step of fatty acid synthesis. Liver carboxylase exists either as catalytically inactive protomers or active filamentous polymers. Citrate, an allosteric activator of the enzyme, is required for both catalysis and polymerization. Glucagon and cAMP cause an immediate decrease in the cytoplasmic citrate concentration of chick liver cells apparently by inhibiting the conversion of glucose to citrate at the phosphofructokinase reaction. Since fatty acid synthesis and citrate level are closely correlated, citrate appears to be a feed-forward activator of the carboxylase in vivo. Compelling evidence indicates that carboxylase filaments are present in the intact cell when citrate levels are high and depolymerize when citrate levels fall. Hence, carboxylase activity and fatty acid synthetic rate appear to be determined by cytoplasmic citrate level.
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PMID:Hormonal regulation of acetyl-CoA carboxylase activity in the liver cell. 4 83

The biochemical explanation for lipid accumulation was investigated principally in Candida 107 and, for comparison, in the non-oleaginous yeast Candida utilis. There were no significant differences between these two yeasts in their control of glucose uptake; in both yeasts, the rates of glucose uptake were independent of the growth rate and were higher in carbon-limited chemostat cultures than in nitrogen-limited cultures. There was no lipid turnover in either yeast, as judged from [14C]acetate uptake and subsequent loss of 14C from the lipid of steady-state chemostat cultures. Acetyl-CoA carboxylase from both yeasts was similar in most characteristics except that from Candida 107 was activated by citrate (40% activation at 1 mM). The enzyme from Candida 107 was relatively unstable and, when isolated from nitrogen-limited (lipid-accumulating) cultures, was accompanied by a low molecular weight inhibitor. The reason for lipid accumulation is attributed to the decrease in the intracellular concentration of AMP as cultures become depleted of nitrogen. As the NAD+-dependent isocitrate dehydrogenase of Candida 107, but not C. utilis, requires AMP for activity, the metabolism of citrate through the tricarboxylic acid cycle in the mitochondria becomes arrested. In Candida 107, but not in C. utilis, there is an active ATP:citrate lyase which converts the accumulating citrate, when it passes into the cytosol, into acetyl-CoA and oxaloacetate. The former product is then available for fatty acid biosynthesis which is stimulated by the high ATP concentration within the cells, by the activation of acetyl-CoA carboxylase by citrate and by the provision of NADPH generated as oxaloacetate is converted via malate to pyruvate. Similar characteristics were evident in oleaginous strains of Rhodotorula glutinis and Mucor circinelloides but not in non-oleaginous representatives of these species.
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PMID:A biochemical explanation for lipid accumulation in Candida 107 and other oleaginous micro-organisms. 4 15

Labeling experiments with chicken liver cell monolayers and suspensions show that glucagon and N6, O2-dibutyryladenosine 3':5'-cyclic monophosphate (dibutyryl cyclic AMP) block fatty acid synthesis from acetate without appreciably affecting cholesterogenesis from acetate or acylglyceride synthesis from palmitate. Neither acetyl-CoA carboxylase [acetyl-CoA:carbon-dioxide ligase (ADP-forming), EC 6.4.1.2] activity assayed in the presence of citrate nor fatty acid synthetase activity is decreased in extracts of cells treated with glucagon. However, the cytoplasmic concentration of citrate, a required allosteric activator of acetyl-CoA carboxylase, is depressed more than 90% by glucagon or dibutyrl cyclic AMP. Pyruvate or lactate largely prevents the inhibitory action of these effectors on fatty acid synthesis by causing a large increase in cytoplasmic citrate level. Thus, it appears that glucagon, acting via cyclic AMP, inhibits fatty acid synthesis by blocking the formation of citrate, an essential activator of acetyl-CoA carboxylase.
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PMID:Mechanism for acute control of fatty acid synthesis by glucagon and 3':5'-cyclic AMP in the liver cell. 19 2


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