Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:6.2.1.1 (ACS)
 78,556 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The acetate activating system of Acetobacter aceti has been studied. The enzyme responsible, acetyl-CoA synthetase, has been purified about 500-fold from crude cell extracts and was approximately 85% pure as judged by polyacrylamide gel electrophoresis in sodium dodecyl sulphate. The purified enzyme showed optimal activity at pH 7.6 in both Tris-HCL and potassium phosphate buffers. In its purest form, the enzyme was stable at 4 degrees-C but denatured upon freezing. The Km values for CoA, ATP and acetate were found to be 0.104 mM, 0.36 mM and 0.25 mM respectively; propionate and acrylate were also activated by the enzyme but not butyrate, isobutyrate or valerate. GTP, UTP, CTP and ADP could not replace ATP in the reaction, and cysteine or pantetheine failed to replace CoA. The cationic requirements were studied and of the divalent cations tested, only Mn2+ could significantly replace Mg2+ in the reaction; K+ and NH4+ stimulated enzyme activity but inhibited at high concentrations; Na+ was a poor activator, but did not inhibit at higher concentrations. The effect of a number of glucose and other metabolites on enzyme activity has been tested.
 ...
PMID:Characterization of the acetyl-CoA synthetase of Acetobacter aceti. 1

A series of 5-alkyl-5-phenylbarbituric acid analogues were shown to be potent hypolipidemic agents in rats and mice at 20 mg/kg/day. This dose is lower than that required for hypolipidemic activity for clofibrate and nicotinic acid derivatives in rodents and man. These new derivatives reduced both serum cholesterol and triglyceride levels in rodents by either the oral or intraperitoneal route of administration. Previous studies have demonstrated that similar heterocyclic compounds, i.e. cyclic imides, glutarimides and hydantoins are potent hypolipidemic agents in rodents. The barbituric acid derivatives probably interfered with de novo synthesis of cholesterol and fatty acids in the early steps since the agents inhibit the activities of ATP-dependent citrate lyase and acetyl-CoA synthetase. Triglyceride synthesis may be blocked since the agents inhibited the rate limiting enzyme, sn-glycerol-3-phosphate-acyl-transferase. Rat tissue lipids especially cholesterol and triglycerides were reduced after 14 days treatment. Fecal lipids were increased in cholesterol and phospholipid content by selected compounds. The rat serum lipoprotein after 14 days drug administration showed reduced VLDL-cholesterol and HDL-triglyceride contents. The modulation of the lipid content of the serum lipoproteins by the barbituric acids suggest that these agents may be helpful in treating clinical hyperlipidemic disease states.
 ...
PMID:Hypolipidemic activity in rodents of phenobarbital and related derivatives. 228 80

On the basis of enzyme activities detected in extracts of Selenomonas ruminantium HD4 grown in glucose-limited continuous culture, at a slow (0.11 h-1) and a fast (0.52 h-1) dilution rate, a pathway of glucose catabolism to lactate, acetate, succinate, and propionate was constructed. Glucose was catabolized to phosphoenol pyruvate (PEP) via the Emden-Meyerhoff-Parnas pathway. PEP was converted to either pyruvate (via pyruvate kinase) or oxalacetate (via PEP carboxykinase). Pyruvate was reduced to L-lactate via a NAD-dependent lactate dehydrogenase or oxidatively decarboxylated to acetyl coenzyme A (acetyl-CoA) and CO2 by pyruvate:ferredoxin oxidoreductase. Acetyl-CoA was apparently converted in a single enzymatic step to acetate and CoA, with concomitant formation of 1 molecule of ATP; since acetyl-phosphate was not an intermediate, the enzyme catalyzing this reaction was identified as acetate thiokinase. Oxalacetate was converted to succinate via the activities of malate dehydrogenase, fumarase and a membrane-bound fumarate reductase. Succinate was then excreted or decarboxylated to propionate via a membrane-bound methylmalonyl-CoA decarboxylase. Pyruvate kinase was inhibited by Pi and activated by fructose 1,6-bisphosphate. PEP carboxykinase activity was found to be 0.054 mumol min-1 mg of protein-1 at a dilution rate of 0.11 h-1 but could not be detected in extracts of cells grown at a dilution rate of 0.52 h-1. Several potential sites for energy conservation exist in S. ruminantium HD4, including pyruvate kinase, acetate thiokinase, PEP carboxykinase, fumarate reductase, and methylmalonyl-CoA decarboxylase. Possession of these five sites for energy conservation may explain the high yields reported here (56 to 78 mg of cells [dry weight] mol of glucose-1) for S. ruminantium HD4 grown in glucose-limited continuous culture.
 ...
PMID:Pathway and sites for energy conservation in the metabolism of glucose by Selenomonas ruminantium. 314 85

2-(2,4-Dimethylphenyl)indan-1,3-dione was shown to be a potent hypolipidemic agent in rodents, lowering significantly both serum cholesterol and triglyceride levels at 20 mg/kg/day. The agent in vivo inhibited the enzymatic activities of ATP-dependent citrate lyase, acetyl-CoA synthetase, cholesterol-7-alpha-hydroxylase, acyl-CoA cholesterol acyl transferase, sn-glycerol-3-phosphate acyl transferase and phosphatidylate phosphohydrolase. Tissue lipid levels of liver and small intestine also were reduced by the agent. The rat serum lipoprotein lipid content was modulated by the drug, which should be favorable for the removable of cholesterol from peripheral tissue for conduction to the liver for clearance from the body. Low density lipoprotein (LDL) cholesterol levels were reduced after treatment, which suggests that the agent potentially reduces deposition of cholesterol in plaques. If chemotherapy for atherosclerosis is to be successful, then the high density lipoprotein (HDL) cholesterol level needs to be elevated more than 16% to 25%, the level produced by current hypolipidemic agents. 2-(2,4-Dimethylphenyl)indan-1,3-dione offers a 75% increase in HDL cholesterol levels and a 30% reduction of LDL cholesterol levels with a suppression of de novo synthesis of lipids and a reduction of tissue cholesterol deposition.
 ...
PMID:Effects of 2-(2,4-dimethylphenyl)indan-1,3-dione on serum lipoprotein and lipid metabolism of rodents. 318 7

The biochemical defect in the mutant Chinese hamster ovary cell lines Clone 13 (Briles, E. B., Li, E., and Kornfeld, S. (1977). J. Biol. Chem. 252, 1107-1116) and Lec8 (Stanley, P. (1980) ACS Symp. Ser. 128, 214-221) was examined. These two mutants, which belong to the same genetic complementation group, were shown in previous studies to exhibit an 80-90% reduction in galactosylation and sialylation of proteins and lipids when compared to wild-type cells. The same studies, however, demonstrated that the mutants were not deficient in the corresponding sugar nucleotides, glycosyltransferases, and endogenous acceptors for these transferases. We now provide evidence strongly suggesting that the primary defect in Lec8 and Clone 13 cells is their inability to translocate UDP-galactose into the lumen of the Golgi apparatus. Golgi vesicles from Lec8 and Clone 13 CHO glycosylation mutants translocate in vitro UDP-galactose at only 3-5% the rate of vesicles from wild-type CHO cells. The deficiency is specific because vesicles from the mutant cells can translocate adenosine 3'-phosphate 5'-phosphosulfate, UDP-N-acetylglucosamine, and UDP-N-acetylgalactosamine at rates comparable to those of vesicles from wild-type cells. These studies also suggest that sugar nucleotides sharing a common uridine nucleotide utilize different translocators present in the Golgi membrane in vivo. The consequence of the above-described mutations and the resulting block in galactosylation of macromolecules in vivo on the translocation of CMP-sialic acid into the Golgi lumen was also examined. As expected, Golgi apparatus vesicles from Lec8 cells were unable to incorporate sialic acid into (endogenous) macromolecules. However, the vesicles were able to transport CMP-sialic acid into their lumen, although the rate of translocation was only 17% of that of wild-type-derived Golgi vesicles.
 ...
PMID:Mechanism of galactosylation in the Golgi apparatus. A Chinese hamster ovary cell mutant deficient in translocation of UDP-galactose across Golgi vesicle membranes. 351 Feb 3

Simple and sensitive spectrophotometric and radiochemical procedures are described for the assay of acetyl-CoA:arylamine N-acetyltransferase (NAT; EC 2.3.1.5), which catalyzes the reaction acetyl-CoA + arylamine----N-acetylated arylamine + CoASH. The methods are applicable to crude tissue homogenates and blood lysates. The spectrophotometric assay is characterized by two features: (i) NAT activity is measured by quantifying the disappearance of the arylamine substrate as reflected by decreasing Schiff's base formation with dimethylaminobenzaldehyde. (ii) During the enzymatic reaction, the inhibitory product CoASH is recycled by the system acetyl phosphate/phosphotransacetylase to the substrate acetyl-CoA. The radiochemical procedure depends on enzymatic synthesis of [3H]acetyl-CoA in the assay using [3H]acetate, ATP, CoASH, and acetyl-CoA synthetase. NAT activity is measured by quantifying N-[3H]acetylarylamine after separation from [3H]acetate by extraction. Product inhibition by CoASH is prevented in this system by the use of acetyl-CoA synthetase.
 ...
PMID:New spectrophotometric and radiochemical assays for acetyl-CoA: arylamine N-acetyltransferase applicable to a variety of arylamines. 401 68

1. A method is described for extracting separately mitochondrial and extramitochondrial enzymes from fat-cells prepared by collagenase digestion from rat epididymal fat-pads. The following distribution of enzymes has been observed (with the total activities of the enzymes as units/mg of fat-cell DNA at 25 degrees C given in parenthesis). Exclusively mitochondrial enzymes: glutamate dehydrogenase (1.8), NAD-isocitrate dehydrogenase (0.5), citrate synthase (5.2), pyruvate carboxylase (3.0); exclusively extramitochondrial enzymes: glucose 6-phosphate dehydrogenase (5.8), 6-phosphogluconate dehydrogenase (5.2), NADP-malate dehydrogenase (11.0), ATP-citrate lyase (5.1); enzymes present in both mitochondrial and extramitochondrial compartments: NADP-isocitrate dehydrogenase (3.7), NAD-malate dehydrogenase (330), aconitate hydratase (1.1), carnitine acetyltransferase (0.4), acetyl-CoA synthetase (1.0), aspartate aminotransferase (1.7), alanine aminotransferase (6.1). The mean DNA content of eight preparations of fat-cells was 109mug/g dry weight of cells. 2. Mitochondria showing respiratory control ratios of 3-6 with pyruvate, about 3 with succinate and P/O ratios of approaching 3 and 2 respectively have been isolated from fat-cells. From studies of rates of oxygen uptake and of swelling in iso-osmotic solutions of ammonium salts, it is concluded that fat-cell mitochondria are permeable to the monocarboxylic acids, pyruvate and acetate; that in the presence of phosphate they are permeable to malate and succinate and to a lesser extent oxaloacetate but not fumarate; and that in the presence of both malate and phosphate they are permeable to citrate, isocitrate and 2-oxoglutarate. In addition, isolated fat-cell mitochondria have been found to oxidize acetyl l-carnitine and, slowly, l-glycerol 3-phosphate. 3. It is concluded that the major means of transport of acetyl units into the cytoplasm for fatty acid synthesis is as citrate. Extensive transport as glutamate, 2-oxoglutarate and isocitrate, as acetate and as acetyl l-carnitine appears to be ruled out by the low activities of mitochondrial aconitate hydratase, mitochondrial acetyl-CoA hydrolyase and carnitine acetyltransferase respectively. Pathways whereby oxaloacetate generated in the cytoplasm during fatty acid synthesis by ATP-citrate lyase may be returned to mitochondria for further citrate synthesis are discussed. 4. It is also concluded that fat-cells contain pathways that will allow the excess of reducing power formed in the cytoplasm when adipose tissue is incubated in glucose and insulin to be transferred to mitochondria as l-glycerol 3-phosphate or malate. When adipose tissue is incubated in pyruvate alone, reducing power for fatty acid, l-glycerol 3-phosphate and lactate formation may be transferred to the cytoplasm as citrate and malate.
 ...
PMID:The intracellular localization of enzymes in white-adipose-tissue fat-cells and permeability properties of fat-cell mitochondria. Transfer of acetyl units and reducing power between mitochondria and cytoplasm. 439 82

1. Transient and steady-state changes caused by acetate utilization were studied in perfused rat heart. The transient period occupied 6min and steady-state changes were followed in a further 6min of perfusion. 2. In control perfusions glucose oxidation accounted for 75% of oxygen utilization; the remaining 25% was assumed to represent oxidation of glyceride fatty acids. With acetate in the steady state, acetate oxidation accounted for 80% of oxygen utilization, which increased by 20%; glucose oxidation was almost totally suppressed. The rate of tricarboxylate-cycle turnover increased by 67% with acetate perfusion. The net yield of ATP in the steady state was not altered by acetate. 3. Acetate oxidation increased muscle concentrations of acetyl-CoA, citrate, isocitrate, 2-oxoglutarate, glutamate, alanine, AMP and glucose 6-phosphate, and lowered those of CoA and aspartate; the concentrations of pyruvate, ATP and ADP showed no detectable change. The times for maximum changes were 1min, acetyl-CoA, CoA, alanine and AMP; 6min, citrate, isocitrate, glutamate and aspartate; 2-4min, 2-oxoglutarate. Malate concentration fell in the first minute and rose to a value somewhat greater than in the control by 6min. There was a transient and rapid rise in glucose 6-phosphate concentration in the first minute superimposed on the slower rise over 6min. 4. Acetate perfusion decreased the output of lactate, the muscle concentration of lactate and the [lactate]/[pyruvate] ratio in perfusion medium and muscle in the first minute; these returned to control values by 6min. 5. During the first minute acetate decreased oxygen consumption and lowered the net yield of ATP by 30% without any significant change in muscle ATP or ADP concentrations. 6. The specific radioactivities of cycle metabolites were measured during and after a 1min pulse of [1-(14)C]acetate delivered in the first and twelfth minutes of acetate perfusion. A model based on the known flow rates and concentrations of cycle metabolites was analysed by computer simulation. The model, which assumed single pools of cycle metabolites, fitted the data well with the inclusion of an isotope-exchange reaction between isocitrate and 2-oxoglutarate+bicarbonate. The exchange was verified by perfusions with [(14)C]bicarbonate. There was no evidence for isotope exchange between citrate and acetyl-CoA or between 2-oxoglutarate and malate. There was rapid isotope equilibration between 2-oxoglutarate and glutamate, but relatively poor isotope equilibration between malate and aspartate. 7. It is concluded that the citrate synthase reaction is displaced from equilibrium in rat heart, that isocitrate dehydrogenase and aconitate hydratase may approximate to equilibrium, that alanine aminotransferase is close to equilibrium, but that aspartate transamination is slow for reasons that have yet to be investigated. 8. The slow rise in citrate concentration as compared with the rapid rise in that of acetyl-CoA is attributed to the slow generation of oxaloacetate by aspartate aminotransferase. 9. It is proposed that the tricarboxylate cycle may operate as two spans: acetyl-CoA-->2-oxoglutarate, controlled by citrate synthase, and 2-oxoglutarate-->oxaloacetate, controlled by 2-oxoglutarate dehydrogenase; a scheme for cycle control during acetate oxidation is outlined. The initiating factors are considered to be changes in acetyl-CoA, CoA and AMP concentrations brought about by acetyl-CoA synthetase. 10. Evidence is presented for a transient inhibition of phosphofructokinase during the first minute of acetate perfusion that was not due to a rise in whole-tissue citrate concentration. The probable importance of metabolite compartmentation is stressed.
 ...
PMID:Control of the tricarboxylate cycle and its interactions with glycolysis during acetate utilization in rat heart. 544 22

1. The overall metabolic changes in lactating mammary gland in alloxan-diabetic and anti-insulin-serum-treated rats were assessed by measurement of the incorporation of (14)C from specifically labelled glucose, pyruvate and acetate into carbon dioxide and lipid, together with measurements of enzymes concerned with the pentose phosphate pathway and with citrate metabolism. 2. Alloxan-diabetes depressed the rate of formation of (14)CO(2) from [1-(14)C]glucose and [2-(14)C]glucose to approx. 10% of the control rate; this was partially reversed by addition of insulin in vitro. The quotient Oxidation of [1-(14)C]glucose/Oxidation of [6-(14)C]glucose fell from a value of 17.6 in the control group to 3.9 in the diabetic group and was restored to 14.3 in the presence of insulin in vitro. In keeping with these results it was shown that glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities were significantly decreased in alloxan-diabetic rats. 3. Alloxan-diabetes depressed the decarboxylation and the oxidation of labelled pyruvate, but not the oxidation of labelled acetate. 4. The synthesis of lipid from specifically labelled glucose was greatly decreased, that from [2-(14)C]pyruvate was almost unchanged and that from [1-(14)C]acetate alone was increased in alloxandiabetic rats. However, the stimulation of lipid synthesis from acetate by glucose was small in the alloxan-diabetic rats compared with the controls. Insulin in vitro partially reversed all these effects. Both citrate-cleavage enzyme and acetate thiokinase activities were decreased in alloxan-diabetic rats. 5. Treatment of rats with anti-insulin serum depressed the formation of (14)CO(2) from [1-(14)C]glucose and [2-(14)C]glucose, but increased that from [6-(14)C]glucose. This was completely restored by the presence of insulin in vitro. The quotient Oxidation of [1-(14)C]glucose/Oxidation of [6-(14)C]glucose fell from a value of 17.6 in the control group to 3.8 in the anti-insulin-serum-treated group. There were no changes in the activity of glucose 6-phosphate dehydrogenase or 6-phosphogluconate dehydrogenase, but the hexokinase distribution changed and the content of the soluble fraction increased significantly. 6. The synthesis of lipid from specifically labelled glucose was depressed in anti-insulin-serum-treated rats; this effect was completely reversed by addition of insulin in vitro to the tissue slices.
 ...
PMID:Effect of alloxan-diabetes and treatment with anti-insulin serum on pathways of glucose metabolism in lactating rat mammary gland. 569 42

Saccharin analogues were observed to be potent antihyperlipidemic agents at 20 mg/kg/day in rodents, significantly reducing both serum cholesterol and triglyceride levels in both normal and atherogenic mice. The saccharin analogues suppressed in vitro and in vivo liver enzymatic activity of acetyl-CoA synthetase, citrate lyase, and mitochondrial citrate exchange leading to a reduction of available cytoplasmic acetyl-CoA, which is required for the synthesis of cholesterol and fatty acids. Liver acetyl-CoA carboxylase, phosphatidate phosphohydralase, and glycerol-3-phosphate acyl transferase activities were markedly reduced by the saccharin analogues. Suppression of these enzymes would lead to a reduction of triglyceride synthesis. The saccharin analogues accelerated bile excretion of cholesterol metabolites and increased the fecal excretion of the cholesterol, triglycerides, neutral lipids, and phospholipids. The liver and plasma lipoprotein lipid content (including cholesterol, triglycerides, and neutral lipids) was markedly reduced by the saccharin analogues, whereas phospholipid content was elevated. The reduction of lipid content of serum chylomicron, very low-density, low-density, and high-density lipoprotein fractions by the saccharin analogues indicates that these agents may be useful in controlling hyperlipidemic diseases where specific lipoprotein fractions are elevated.
 ...
PMID:Antihyperlipidemic activity of saccharin analogues in rodents. 664 71


1 2 3 4 5 6 7 8 9 10 Next >>