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)

A protein kinase which phosphorylates and inactivates acetyl-CoA carboxylase has been purified to apparent homogeneity from rat liver. The kinase was found to exist in two forms: bound to carboxylase in a complex or in a free form that is in different stages of aggregation over a wide range of molecular weights. The purification of the kinase involved first partial purification of acetyl-CoA carboxylase through polyethylene glycol precipitation and DEAE-cellulose chromatography. The kinase was then separated from acetyl-CoA carboxylase by Sepharose 2B chromatography. The molecular weight of the kinase subunit was 170,000 as determined by sodium dodecyl sulfate-gel electrophoresis. The incorporation of 1 mol of phosphate/mole of carboxylase subunit caused complete inactivation of the carboxylase. Acetyl-CoA carboxylase, inactivated by the kinase, can be dephosphorylated and reactivated when incubated with phosphorylase phosphatase. The Km values of the kinase for acetyl-CoA carboxylase and ATP are 90 nM and 20 microM, respectively. The kinase was found to be cyclic AMP-independent, but activated by CoA. The protein kinase can phosphorylate acetyl-CoA carboxylase, protamine, and histones, but could not act on hydroxymethylglutaryl-CoA reductase or phosphorylase b.
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PMID:Purification and properties of a kinase which phosphorylates and inactivates acetyl-CoA carboxylase. 612 Jan 70

The nature of the protein phosphatases involved in the regulation of glycolysis/gluconeogenesis, fatty acid synthesis and cholesterol synthesis in rat liver has been investigated using L-pyruvate kinase, ATP-citrate lyase, acetyl-CoA carboxylase and hydroxymethylglutaryl-CoA reductase as substrates. The results show that protein phosphatases-1, 2A and 2C are the only significant protein phosphatases in rat liver acting on these four substrates. The relationship of these three enzymes to other protein phosphatases described in the literature is discussed.
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PMID:The protein phosphatases involved in cellular regulation. 3. Fatty acid synthesis, cholesterol synthesis and glycolysis/gluconeogenesis. 630 26

Methods were developed for quantifying protein phosphatases-1, 2A, 2B and 2C in cell extracts, and these procedures were exploited to determine their tissue and subcellular distributions. In addition, the contribution of each enzyme to the total protein phosphatase activity in skeletal muscle and liver extracts towards nine proteins involved in the control of glycogen metabolism, glycolysis/gluconeogenesis, fatty acid synthesis and cholesterol synthesis was assessed. Each protein phosphatase was present at significant concentrations in skeletal muscle, heart muscle, liver, brain and adipose tissue, although the relative amounts differed considerably. In skeletal muscle, protein phosphatase-1 was the major enzyme acting on phosphorylase, glycogen synthase and phosphorylase kinase (beta-subunit), and thus was the major protein phosphatase responsible for the inactivation of glycogenolysis and stimulation of glycogen synthesis. This idea was reinforced by the observation that 50% of the protein phosphatase-1 activity was associated with the protein-glycogen complex. In the liver, protein phosphatases-1, 2A and 2C each appear to play a role in the regulation of glycogen metabolism. Protein phosphatase-1 accounted for a significant fraction of the total potential activity towards phosphorylase and glycogen synthase, and was the major phosphorylase kinase (beta-subunit) phosphatase of this tissue. In addition, it was the only protein phosphatase present in the protein-glycogen complex. Protein phosphatase 2A was also a major phosphorylase phosphatase and glycogen synthase phosphatase in this tissue. Protein phosphatase 2C was a significant glycogen synthase phosphatase in the liver, but had negligible activity toward phosphorylase or phosphorylase kinase (beta-subunit). In the absence of Ca2+, protein phosphatase 2A was the major phosphorylase kinase (alpha-subunit) phosphatase and the only inhibitor-1 phosphatase, in skeletal muscle or liver. In the presence of Ca2+, protein phosphatase 2B accounted for most of the activity towards these substrates. Protein phosphatase 2A was the major enzyme acting on L-pyruvate kinase, ATP-citrate lyase and acetyl-CoA carboxylase in rat liver, suggesting an important role in the regulation of glycolysis/gluconeogenesis and fatty acid synthesis. Protein phosphatase 2C was the major enzyme acting on hydroxymethylglutaryl-CoA (HMG-CoA) reductase and HMG-CoA reductase kinase, suggesting an important role in the regulation of cholesterol synthesis. However, the observation that 20% of the protein phosphatase-1 in liver was associated with the microsomal fraction suggests that this enzyme may also be involved in regulating HMG-CoA reductase, which is tightly associated with microsomes. The activity of protein phosphatase-1 in dilute skeletal muscle and liver extracts was just as sensitive to inhibitor-1 and inhibitor-2 as the purified enzyme. In concentrated extracts, higher concentrations of the inhibitor proteins were required and the inhibition was time-dependent...
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PMID:The protein phosphatases involved in cellular regulation. 6. Measurement of type-1 and type-2 protein phosphatases in extracts of mammalian tissues; an assessment of their physiological roles. 630 29

Studies of lipid metabolism in cell cultures are usually carried out after preincubation of cells in media containing lipoprotein-deficient or delipidated serum. The artifacts produced during delipidation prevent the standardization of assays and the study of the role of hormones on lipid metabolism. We studied the effects of triiodothyronine, hydrocortisone, insulin and their combination on cholesterol and fatty acid synthesis in cultured human skin fibroblasts preincubated for 24 h in an artificial medium (medium A) consisting of equal volumes of Dulbecco's modified Eagle's and Ham's F-12 media enriched with transferrin, biotin and calcium pantothenate. In cells preincubated in medium A the incorporation of acetate to cholesterol and the activity of hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase were much lower than in cells preincubated in standard medium containing lipoprotein-deficient serum. Addition of the three hormones caused a marked stimulation of the incorporation of acetate to cholesterol (from 3.1 to 17.7 pmol/min per mg protein), an activity similar to that in cells preincubated in lipoprotein-deficient serum plus hormones. The stimulatory effect of the hormones on HMG-CoA reductase activity was smaller, from 11 to 26 pmol/min per mg protein compared to 83 pmol/min per mg protein in cells preincubated in lipoprotein-deficient serum plus hormones. Most of the stimulatory effect was due to insulin. The lack of coordinate response between these two parameters in cells preincubated in artificial medium could not be explained by (a) stimulation of a post-mevalonate step as measured by the incorporation of mevalonate to cholesterol; (b) the in vitro inactivation of HMG-CoA reductase by phosphorylation: incubation of fibroblast microsomes with Escherichia coli alkaline phosphatase resulted in a decrease in HMG-CoA reductase activity, in contrast to an increase in hepatic microsomes; (c) the presence of inhibitors of HMG-CoA reductase in the microsomal extract. In cells preincubated in medium A the incorporation of acetate to fatty acids and the activities of acetyl-CoA carboxylase and fatty acid synthetase were approximately equal to that of cells preincubated in standard medium containing lipoprotein-deficient serum. Hormones added to medium A caused a stimulation of incorporation of acetate to fatty acids (from 5.1 to 19.8 pmol/min per mg protein), the activity of acetyl-CoA carboxylase (from 494 to 820 pmol/min per mg protein) and of fatty acid synthetase (from 300 to 678 pmol/mg protein). These values were significantly higher than those obtained in cells preincubated with lipoprotein-deficient serum with or without hormones.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The effects of triiodothyronine, hydrocortisone and insulin on lipid synthesis by cultured fibroblasts preincubated in a serum-free medium. 636 71

The effects of tunicamycin on 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity and cholesterol biosynthesis have been studied in cultured C-6 glial cells. Depending on culture conditions, exposure to tunicamycin caused either a marked inhibition of induction of HMG-CoA reductase activity or, under steady state conditions, a marked reduction in enzymatic activity. Incorporation of [14 C]acetate into sterols was affected similarly. After a 24-h exposure, a 50% reduction in reductase activity was observed with a concentration of 0.05 micrograms/ml, and a maximal, 65-70% reduction occurred with 0.10 micrograms/ml of the drug. The effect of tunicamycin on reductase activity and on sterol synthesis was apparent 4 h after addition of the drug and nearly maximal after 6 h. The relative specificity of the effect of tunicamycin was indicated by the finding of no change in the activities of NADPH-cytochrome c reductase, acetyl-CoA carboxylase, or fatty acid synthetase, in incorporation of [3H]leucine into total protein, or in the rate of increase in cellular protein and phospholipid at concentrations of tunicamycin that caused the marked effect on HMG-CoA reductase. The reversibility of the effect of tunicamycin was shown by observing total recovery of reductase activity within 24 h after removal of the drug following a 24-h exposure. That the effect of tunicamycin on reductase is related to the drug's effect on glycoprotein synthesis was shown in two ways. First, the range of concentrations over which tunicamycin led to the decrease in reductase activity was essentially identical with the range over which the drug led to a decrease in incorporation of [3H]mannose into protein. Second, incubation of C-6 cells with N-acetylglucosamine simultaneously with tunicamycin was accompanied by prevention of the drug's effect on both HMG-CoA reductase and glycoprotein synthesis. These data suggest that glycoprotein synthesis is necessary for the expression of HMG-CoA reductase activity and, thereby, cholesterol synthesis in glial cells. Moreover, a link between glycoprotein and cholesterol biosynthesis could play a role in the mediation of certain maturational events in cells of neural origin.
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PMID:Effect of tunicamycin on 3-hydroxy-3-methylglutaryl coenzyme A reductase in C-6 glial cells. 687 86

Swine were fed corn- or barley-based diets with, or without, culture filtrate (CF) of Trichoderma viride for 21 days. Weight gains were nonsignificantly but slightly increased by CF. The activities of beta-hydroxy-beta-methylglutaryl coenzyme A (HMG-CoA) reductase, cholesterol 7 alpha-hydroxylase, acetyl-CoA carboxylase (ACX), fatty acid synthetase (FAS) and other lipogenic enzymes in several tissues were determined. Significant decreases in the activities of HMG-CoA reductase and cholesterol 7 alpha-hydroxylase in all tissues of swine fed the CF-diets were observed. The major site for the regulation of cholesterol biosynthesis was adipose tissue followed by the intestine, liver, lung and muscle in order of activity. The concentrations of cholesterol in serum and muscle were decreased 27% and 23%, respectively, by CF. ACX and FAS activities increased ca. 2-fold when CF was fed with either of the cereal-based diets. The major sites for fatty acid synthesis was the adipose tissue and, to a lesser extent, the liver. Very low rates of synthesis were detected in intestine, lung and muscle. Similar distributions of activities were found for related lipogenic enzymes.
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PMID:Effects of cereals and culture filtrate of Trichoderma viride on lipid metabolism of swine. 689 42

Various physical fractions of the barley kernel were fed to one-day-old female and male chickens to determine their effect on hepatic beta-hydroxy-beta-methylglutaryl coenzyme A (HMG-CoA) reductase, cholesterol 7 alpha-hydroxylase and the lipogenic enzymes, acetyl-CoA carboxylase (ACX), malic enzyme (ME), citrate-cleavage enzyme (CCE) and fatty acid synthetase (FAS) at the subcellular level. Significant inhibition (p less than 0.01) of cholesterol biosynthesis accompanied by significant decreases in plasma cholesterol concentrations and induction of fatty acid synthesis were found in diets based on pearled barley, barley pearlings and a high-protein barley flour (HPBF: aleurone and subaleurone layers of barley endosperm) separated from the pearlings when compared to corn. Lower weight gains in 1- to 4-week-old birds fed the high-protein barley flour were found to be the result of lower feed consumption; pair feeding of 12-week-old birds with diets based on corn and high-protein barley flour produced equal weight gains in both treatments and significant reductions in hepatic HMG-CoA reductase, plasma cholesterol and induction in several lipogenic enzymes in birds fed the high-protein barley flour. Substitutions of 5-20% high-protein barley flour for corn in a corn-based diet produced significant weight gains (p less than 0.01) of 10 to 20% in 2-week-old chickens, inhibited cholesterol biosynthesis by 45-65% and produced a 3-fold increase in a fatty acid synthetase. The results indicate that HPBF contains an inhibitor(s) of cholesterol biosynthesis and a growth factor(s) when compared to a corn-based diet.
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PMID:Effects of different fractions of the barley kernel on the hepatic lipid metabolism of chickens. 716 70

The possibility of biosynthesis of cholic (I) and chenodeoxycholic (II) acids from [1-14C]acetyl-CoA and [2-14C]malonyl-CoA in a reconstituted system of rat liver and the incorporation of acetyl-CoA into these bile acids under conditions of acetyl-CoA carboxylase activation by citrate or its inhibition by avidin were studied. The effects of Triton WR 1339 and cholesterol feeding on acetyl-CoA and malonyl-CoA incorporation into I and II were investigated. Teh incorporation of both substrates into the total unsaponifiable lipid fraction and fatty acids was demonstrated. The reconstituted system of rat liver was found able to synthesize and I and II not only from acetyl-CoA, but from malonyl-CoA as well. The rate of malonyl-CoA incorporation into the bile acids was somewhat higher than that of acetyl-CoA incorporation. Preincubation of the reconstituted system with citrate stimulated the rate of acetyl-CoA incorporation into I. Stimulation of biosynthesis of I occurred independently of the diurnal rhythm of the 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA reductase) activity. An addition of avidin to the reconstituted system preincubated with citrate caused inhibition of acetyl-CoA incorporation both into fatty acids and into I. The rate of biosynthesis of II remained practically unchanged in both cases. Treatment with Triton WR 1339 had only a slight effect, while cholesterol feeding significantly stimulated the incorporation of acetyl-CoA and malonyl-CoA into I and II. The results obtained suggest the participation of malonyl-CoA in formation of bile acids, preferentially cholic acid, and in a lesser degree, in sterol biosynthesis. Data from stimulation of bile acid biosynthesis under cholesterol feeding suggest that HMG-CoA reductase localized in the soluble fraction of rat liver is involved in bile acid biosynthesis.
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PMID:[Biosynthesis of cholic and chenodeoxycholic acids from [1-14C]acetyl-CoA and [2-14C]malonyl-CoA in a reconstituted system from the rat liver]. 723 4

The 5'-AMP-activated protein kinase (AMPK) regulates the fatty acid and sterol synthesizing pathways via phosphorylation of acetyl-CoA carboxylase and HMG-CoA reductase, respectively. Highly purified kinase from porcine liver contains three apparent subunits of molecular mass 63 kDa, 40 kDa and 38 kDa. Peptide sequencing of the 63 kDa protein (AMPK63cat) revealed that this polypeptide is the catalytic subunit of the kinase. Porcine peptide sequences were used to clone by RT-PCR partial length cDNAs for the catalytic domains of the porcine AMPK63cat, and its rat homolog, which were virtually identical in deduced amino acid sequence. Screening of a rat liver cDNA library with these partial length cDNAs and with degenerate oligonucleotides yielded several unique clones, some of which had a 142 bp deletion in the catalytic domain of the kinase. A consensus full-length sequence with a 1.7 kb open reading frame has been constructed from overlapping library and PCR-derived clones. A large mRNA for rat AMPK63cat (8.5 kb) is expressed in nearly all rat tissues, with highest levels detectable in heart and skeletal muscle. Using PCR, the presence of two mRNA species with or without the 142 bp deletion in the catalytic domain was noted in all rat tissues examined. Comparison of the deduced protein sequence of AMPK63cat reveals highly conserved homologies in both the catalytic and non-catalytic domains to several members of the SNF1 kinase family, including kinases from Arabidopsis, barley, rye, and S. cerevesiae, as well as to other mammalian kinases and to a C. elegans kinase. The high evolutionary conservation of both kinase structure and function (metabolite sensing) coupled with their pattern of tissue/organism expression suggest that the mammalian members of this kinase family likely play wider roles than the regulation of cellular lipid metabolism.
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PMID:Catalytic subunits of the porcine and rat 5'-AMP-activated protein kinase are members of the SNF1 protein kinase family. 771 24

To investigate the importance of factors influencing substrate availability for triacylglycerol biosynthesis on lipoprotein metabolism, the effects of two opposite-acting sulphur-substituted fatty acid analogues, tetradecylthioacetic acid and tetradecylthiopropionic acid were studied. Administration of tetradecylthioacetic acid to rats resulted in a reduction of plasma levels of triacylglycerols (44%) and cholesterol (26%). This was accompanied by a reduction in very-low-density lipoprotein (VLDL) triacylglycerols (48%), VLDL cholesterol (36%), low-density lipoprotein (LDL) cholesterol (36%) and high-density lipoprotein (HDL) triacylglycerols (50%), whereas HDL cholesterol levels did not change. Subsequently, the HDL/LDL-cholesterol ratio increased by 40%. The cholesterol-lowering effect was accompanied by a reduction in hydroxymethylglutaryl CoA (HMG-CoA) reductase activity (37%). Both mitochondrial and peroxisomal fatty acid oxidation increased (1.7-fold and 5.3-fold, respectively). Furthermore, there was a significant negative correlation between plasma triacylglycerols and mitochondrial fatty acid oxidation. Hepatic triacylglycerol synthesis was retarded, as indicated by a decrease in VLDL triacylglycerol secretion (40%), and by a reduced liver triacylglycerol content (29%). The activities of lipoprotein lipase and hepatic lipase in post-heparin plasma were not affected. Microsomal and cytosolic phosphatidate phosphohydrolase activities were inhibited (28% and 70%, respectively). Hepatic malonyl-CoA levels decreased by 29% and the total activity of acetyl-CoA carboxylase was reduced (23%). In hepatocytes treated with tetradecylthioacetic acid, mitochondrial fatty acid oxidation increased markedly (100%) and triacylglycerol secretion was reduced (40%). In tetradecylthiopropionic-acid-treated rats, a significant increase in both plasma and VLDL triacylglycerols was found (46% and 72%, respectively) but VLDL triacylglycerol secretion was unaffected. However, no effect on either plasma or lipoprotein cholesterol levels was seen. Mitochondrial fatty acid oxidation was decreased by 50% and hepatic triacylglycerol levels increased by 33%. In hepatocytes exposed to tetradecylthiopropionic acid, triacylglycerol synthesis increased (100%) while triacylglycerol secretion and fatty acid oxidation remained unaltered. The results illustrate that lipoprotein triacylglycerol levels can be modulated by changes in the availability of fatty acid substrate for triacylglycerol biosynthesis, mainly by affecting mitochondrial fatty acid oxidation. In addition, we demonstrate that suppression of rat hepatic HMG-CoA reductase activity during treatment with tetradecylthioacetic acid may contribute to a cholesterol-lowering effect.
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PMID:Hepatic fatty acid metabolism as a determinant of plasma and liver triacylglycerol levels. Studies on tetradecylthioacetic and tetradecylthiopropionic acids. 786 30


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