Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Acetyl-CoA carboxylase (ACC) is regulated in mammalian tissues, in part, by multisite enzyme phosphorylation. Yeast ACC (Y-ACC) has been highly purified from S. cerevisiae by monomeric avidin-Sepharose chromatography, revealing an enzyme subunit species of molecular mass 265,000 Da. Unlike mammalian enzyme, Y-ACC is citrate-independent, and reacts weakly or not at all with a panel of anti-rat liver ACC antibodies. Like rat ACC, Y-ACC is rapidly phosphorylated and inactivated by two mammalian carboxylase kinases, the cAMP-dependent protein kinase and 5'-AMP-stimulated kinase. It is also phosphorylated by rat liver casein kinase II, but without any change in catalytic activity. Three major yeast protein kinases active on ACC have been fractionated; all co-elute with kinases active on casein, but each appears to be a distinct catalytic species. Like the mammalian casein kinases, however, phosphorylation of ACC by these yeast kinases does not alter yeast ACC activity. Taken together, these data indicate that Y-ACC possesses at least two classes of phosphorylation sites, one or more of which acutely regulates enzyme activity. Alterations in Y-ACC phosphorylation in yeast, as in mammalian tissues, could be an important modulator of the rates of fatty acid synthesis.
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PMID:Yeast acetyl-CoA carboxylase: in vitro phosphorylation by mammalian and yeast protein kinases. 197 18

The activities of several hepatic enzymes are preferentially zonated to the periportal or perivenous cells of the liver acinus. Employing dual-digitonin-pulse perfusion of rat liver in the study of acetyl-CoA carboxylase (ACC), we have identified a heretofore unrecognized feature of hepatic zonation, namely an intrahepatic gradient in enzyme specific activity. ACC activity shows a relative periportal localization in normally feeding rats, even when corrected for ACC protein mass. In contrast with results previously reported by us [Evans, Quistorff & Witters (1989) Biochem. J. 259, 821-829], the total mass of both hepatic ACC isoenzymes was not found to differ between the two hepatic zones in the present study. In perfusion eluates from fed animals, periportal ACC displays enhanced citrate reactivity and two kinetic components of acetyl-CoA reactivity; the largest periportal/perivenous gradient (5-fold) is accounted for by a species with a lower Km for acetyl-CoA. The zonal gradient in ACC maximal velocity, measured in eluates from fed rats, does not persist after ACC purification, although the isolated periportal enzyme, like dephosphorylated ACC, has a lower activation constant for citrate. Total ACC protein phosphatase activity is higher in periportal eluates, but no differences in the activities of either a 5'-AMP-activated ACC kinase or the cyclic-AMP-dependent protein kinase are noted between the hepatic zones. The induction of total hepatic ACC mass and specific activity, on fasting/refeeding with a high-carbohydrate diet, abolishes the periportal/perivenous activity gradient, largely owing to a selective activation of perivenous enzyme. Nutritional induction is also accompanied by a marked alteration in ACC acetyl-CoA kinetics and abolition of the gradient in total ACC phosphatase. These studies indicate that hepatic enzyme zonation, which is often attributed to differential expression of enzyme protein, may result from zonal variations in enzyme specific activity, owing to differences in allosteric regulation and/or covalent modification.
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PMID:Hepatic zonation of acetyl-CoA carboxylase activity. 197 69

1. We have synthesized two peptides, one based on the exact sequence around the unique site (Ser79) for the AMP-activated protein kinase on rat acetyl-CoA carboxylase (SSMS peptide) and another in which the serine residue corresponding to the site for cyclic-AMP-dependent protein kinase (Ser77) was replaced by alanine (SAMS peptide). 2. Both peptides were phosphorylated with similar kinetics by the AMP-activated protein kinase, but only the SSMS peptide was a substrate for cyclic-AMP-dependent protein kinase. The SAMS peptide was not phosphorylated by any of five other purified protein kinases tested. 3. The Km of AMP-activated protein kinase for the SAMS peptide is higher than that for acetyl-CoA carboxylase, but the Vmax for peptide phosphorylation is 2.5 times higher than that of its parent protein. This peptide therefore gives a convenient and sensitive assay for the AMP-activated protein kinase. 4. Acetyl-CoA-carboxylase kinase and peptide kinase activities copurify through six steps from a post-mitochondrial supernatant of rat liver, showing that the SAMS peptide is a specific substrate for the AMP-activated protein kinase in this tissue. We could not demonstrate AMP-dependence of the kinase activity in crude preparations, apparently due to endogenous AMP remaining bound to the enzyme. However, 8-bromoadenosine 5-monophosphate (Br8AMP) is a partial agonist at the allosteric (AMP) site, and inhibition by 2 mM Br8AMP can be used to test that one is measuring the AMP-stimulated form of the kinase. 5. Using this approach, we have examined the kinase activity in nine different rat tissues, plus a mouse macrophage cell line, and find that there is a correlation between tissues expressing significant levels of peptide kinase activity and those active in the synthesis or storage of lipids. 6. We also use the peptide assay to show that cyclic AMP-dependent protein kinase does not activate purified AMP-activated protein kinase, and does not affect the activation of partially purified AMP-activated protein kinase by endogenous kinase kinase.
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PMID:Tissue distribution of the AMP-activated protein kinase, and lack of activation by cyclic-AMP-dependent protein kinase, studied using a specific and sensitive peptide assay. 257 67

1. We have purified the AMP-activated protein kinase 4800-fold from rat liver. The acetyl-CoA carboxylase kinase and 3-hydroxy-3-methylglutaryl-CoA(HMG-CoA) reductase kinase activities copurify through all six purification steps and are inactivated with similar kinetics by treatment with the reactive ATP analogue fluorosulphonylbenzoyladenosine. 2. The final preparation contains several polypeptides detectable by SDS/polyacrylamide gel electrophoresis, but only one of these, with an apparent molecular mass of 63 kDa, is labelled using [14C]fluorosulphonylbenzoyladenosine. This is also the only polypeptide in the preparation that becomes significantly labelled during incubation with [gamma 32P]ATP. This autophosphorylation reaction did not affect the AMP-stimulated kinase activity. 3. In the absence of AMP the purified kinase has apparent Km values for ATP and acetyl-CoA carboxylase of 86 microM and 1.9 microM respectively. AMP increases the Vmax 3-5-fold without a significant change in the Km for either protein or ATP substrates. 4. The response to AMP depends on the ATP concentration in the assay, but at a near-physiological ATP concentration the half-maximal effect of AMP occurs at 14 microM. Studies with a range of nucleoside monophosphates and diphosphates, and AMP analogues showed that the allosteric activation by AMP was very specific. ADP gave a small stimulation at low concentrations but was inhibitory at high concentrations. 5. These results show that the AMP-activated protein kinase is the major HMG-CoA reductase kinase detectable in rat liver under our assay conditions and that it is therefore likely to be identical to previously described HMG-CoA reductase kinase(s) which are activated by adenine nucleotides and phosphorylation. The AMP-binding and catalytic domains of the kinase are located on a 63-kDa polypeptide which is subject to autophosphorylation.
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PMID:Purification and characterization of the AMP-activated protein kinase. Copurification of acetyl-CoA carboxylase kinase and 3-hydroxy-3-methylglutaryl-CoA reductase kinase activities. 259 24

The kinetic parameters and phosphorylation state of acetyl-CoA carboxylase were analysed after purification of the enzyme by avidin--Sepharose chromatography from extracts of isolated adipocytes treated with glucagon or adrenaline. The results provide evidence that the mechanism of inhibition of acetyl-CoA carboxylase in adipocytes treated with glucagon [Zammit & Corstorphine (1982) Biochem. J. 208, 783-788] involves increased phosphorylation of the enzyme. Hormone treatment had effects on the kinetic parameters of the enzyme similar to those of phosphorylation of the enzyme in vitro by cyclic AMP-dependent protein kinase. Glucagon treatment of adipocytes led to increased phosphorylation of acetyl-CoA carboxylase in the same chymotryptic peptide as that containing the major site phosphorylated on the enzyme by purified cyclic AMP-dependent protein kinase in vitro [Munday & Hardie (1984) Eur. J. Biochem. 141, 617-627]. The dose--response curves for inhibition of enzyme activity and increased phosphorylation of the enzyme were very similar, with half-maximal effects occurring at concentrations of glucagon (0.5-1 nM) which are close to the physiological range. In general, the patterns of increased 32P-labelling of chymotryptic peptides induced by glucagon or adrenaline were similar, although there were quantitative differences between the effects of the two hormones on individual peptides. The results are discussed in terms of the possible roles of cyclic AMP-dependent and -independent protein kinases in the regulation of acetyl-CoA carboxylase activity and of lipogenesis in white adipose tissue.
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PMID:Evidence that glucagon-mediated inhibition of acetyl-CoA carboxylase in isolated adipocytes involves increased phosphorylation of the enzyme by cyclic AMP-dependent protein kinase. 285 3

ATP-citrate lyase and acetyl-CoA carboxylase purified from lactating rat mammary gland are phosphorylated stoichiometrically by the calmodulin-dependent multiprotein kinase from rabbit skeletal muscle. The reactions are completely dependent on the presence of both Ca2+ and calmodulin. ATP-citrate lyase and acetyl-CoA carboxylase are also phosphorylated stoichiometrically by the Ca2+- and phospholipid-dependent protein kinase (protein kinase C) purified from bovine brain. Phosphorylation of these substrates is stimulated 6-fold and 40-fold respectively by Ca2+ and phosphatidylserine. The calmodulin-dependent and phospholipid-dependent protein kinases phosphorylate the same serine residue on ATP-citrate lyase that is phosphorylated by cyclic-AMP-dependent protein kinase. The sequence of the tryptic peptide containing this site on the mammary enzyme is identical with the sequence of the peptide containing the site on ATP-citrate lyase that is phosphorylated in isolated hepatocytes in response to insulin and/or glucagon. The calmodulin-dependent, phospholipid-dependent and cyclic-AMP-dependent protein kinases phosphorylate distinct sites on acetyl-CoA carboxylase. However, one of the three phosphorylated tryptic peptides derived from enzyme treated with the phospholipid-dependent kinase is identical with the major phosphopeptide (T1) derived from enzyme treated with cyclic-AMP-dependent protein kinase. Phosphorylation of acetyl-CoA carboxylase by the phospholipid-dependent protein kinase inactivates acetyl-CoA carboxylase in a similar manner to cyclic-AMP-dependent protein kinase. With either protein kinase slightly greater phosphorylation and inactivation is seen after pretreatment of acetyl-CoA carboxylase with protein phosphatase-2A, but the effects of the protein phosphatase treatment are not completely reversed. Inactivation by the phospholipid-dependent protein kinase is Ca2+- and phospholipid-dependent, is reversed by protein phosphatase-2A, and correlates with the degree of phosphorylation. The relevance of these findings to insulin- and growth-factor-promoted phosphorylation of ATP-citrate lyase and acetyl-CoA carboxylase in intact cells is discussed.
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PMID:Characterization of the phosphorylation of rat mammary ATP-citrate lyase and acetyl-CoA carboxylase by Ca2+ and calmodulin-dependent multiprotein kinase and Ca2+ and phospholipid-dependent protein kinase. 287 35

Because of certain similarities between acetyl-CoA carboxylase (ACC) and tubulin, and the recent demonstration of the ADP-ribosylation of tubulin by cholera toxin, we have investigated a potential role for ADP-ribosylation in the regulation of ACC activity. Incubation of purified rat liver ACC with cholera toxin in the presence of millimolar concentrations of [adenylate-32P]NAD results in a time-dependent incorporation of ADP-ribose into ACC of greater than 2 mol/mol of enzyme subunit, accompanied by a marked inactivation of enzyme activity. This effect is not mimicked by pertussis toxin, ADP-ribose, or ribose 5-phosphate. Incubation of labeled ACC with snake venom phosphodiesterase and alkaline hydrolysis release 32P-products tentatively identified by high-performance liquid chromatography as 5'-[32P]AMP and [32P]ADP-ribose, respectively. These data are consistent with a mono-ADP-ribosylation of ACC catalyzed by cholera toxin. Phosphodiesterase treatment of inactivated ACC partially restores enzyme activity. The effects of ADP-ribosylation of ACC are expressed both as a decrease in the enzyme Vmax and as an increase in the apparent Ka for citrate. These results suggest that ACC might be a substrate for endogenous ADP-ribosyltransferases and that this covalent modification could be an important regulatory mechanism for the modulation of fatty acid synthesis in vivo.
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PMID:Regulation of acetyl-CoA carboxylase by ADP-ribosylation. 287 58

Relationships between the cyclic AMP content, the rate of lipogenesis and the activity of acetyl-CoA carboxylase in acini prepared from lactating rat mammary tissue were investigated by exposing them to agents that increase their cyclic AMP content in the presence or absence of insulin. The dose-dependent inhibition of lipogenesis by theophylline in acini isolated from fed rats was highly correlated with the induced increases in acinar cyclic AMP content. Cyclic AMP of acini from 24 h-starved lactating rats was more sensitive in its response to theophylline than that in acini from fed animals. Neither forskolin nor a mixture of isoprenaline and Ro 7-2956 were able significantly to change either the rate of lipogenesis or the activity of acetyl-CoA carboxylase in acini from fed rats when added to incubations in vitro, in spite of the large increases in cyclic AMP concentration produced by these agents. Insulin was without effect on the activity of acetyl-CoA carboxylase and on either the basal or isoprenaline-stimulated cyclic AMP content of acini. These results are discussed in terms of the possibility that the rate of lipogenesis and the cyclic AMP content in mammary acini can vary independently of one another and of the activity of acetyl-CoA carboxylase.
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PMID:Modulation of intracellular cyclic AMP content and rate of lipogenesis in mammary acini in vitro. 288 37

Phosphorylation of soluble proteins in rat mammary acinar cells was investigated. When phosphorylation proceeded in intact cells, in the presence of [32P]Pi, the major non-casein phosphoproteins, including acetyl-CoA carboxylase, were unresponsive to incubation conditions that caused major increases in the intracellular concentration of cyclic AMP. The overall 32P specific radioactivity (c.p.m./microgram of protein) of acetyl-CoA carboxylase, assessed after affinity purification of the enzyme with avidin-Sepharose, was unchanged by incubation under such conditions. Furthermore, the distribution of 32P among tryptic phosphopeptides of the enzyme, resolved by reversed-phase h.p.l.c., was not altered by cyclic AMP-increasing treatments of the acinar cells. When cytosol fractions were incubated with [gamma-32P]ATP, some phosphoproteins responded to the addition of micromolar concentrations of dibutyryl cyclic AMP or cyclic AMP by undergoing an enhancement of phosphate incorporation. In these experiments in vitro, protein phosphatase activity did not make a major contribution to the net phosphorylation of individual phosphoproteins, and acetyl-CoA carboxylase was not prominent among the phosphoproteins identified after short (less than 1 min) incubations of cytosols with [gamma-32P]ATP. The resistance of protein phosphorylation to variations in the cyclic AMP concentration in intact mammary epithelial cells, demonstrated by this work, is one of several mechanisms that ensure the pleiotropic refractoriness of those cells to agents which normally cause a stimulation of adenylate cyclase activity in hormone-sensitive cells.
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PMID:Protein phosphorylation in rat mammary acini and in cytosol preparations in vitro. Phosphorylation of acetyl-CoA carboxylase is unaffected by cyclic AMP. 288 90

Superose 6 chromatography was used to separate rapidly the polymeric and dimeric forms of acetyl-CoA carboxylase. With preparations of acetyl-CoA carboxylase purified by Sepharose-avidin chromatography, it is shown that citrate promotes polymerization and that the extent of polymerization is diminished, but not eliminated, after phosphorylation by cyclic-AMP-dependent protein kinase. After exposure of rat epididymal adipose tissue to insulin, evidence was obtained for a marked increase in polymerization. The polymeric form, which was active in the absence of citrate, exhibited increased phosphorylation, particularly on a tryptic peptide designated the I-peptide in an earlier study [Brownsey & Denton (1982) Biochem. J. 202, 77-86]. In contrast, in tissue exposed to the beta-agonist isoprenaline, most of the phosphorylated acetyl-CoA carboxylase appeared to be in the dimeric form if chromatography was carried out in the absence of citrate, whereas in the presence of citrate the degree of polymerization was diminished.
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PMID:Use of rapid gel-permeation chromatography to explore the inter-relationships between polymerization, phosphorylation and activity of acetyl-CoA carboxylase. Effects of insulin and phosphorylation by cyclic AMP-dependent protein kinase. 288 91


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