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:6.2.1.1 (ACS)
78,556 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adventitious redox-active metals in Krebs-Henseleit buffer exhibit a significant enhancement of damage to isolated rat hearts. Using atomic absorption spectroscopy, it was determined that Krebs-Henseleit buffer contains substantial amounts of contaminating iron and copper. Significant copper contamination was found in ACS Reagent grade sodium chloride and sodium bicarbonate; iron contamination in sodium chloride, potassium chloride, sodium bicarbonate, and calcium chloride. Chelating resin treatment of individual reagents was found to decrease copper content of Krebs-Henseleit buffer from 0.32 to 0.17 microM. Using salicylate as a probe for .OH formation, it was determined that considerable amounts of this radical are formed when 0.25 mM ascorbate is added to the buffer indicating significant metal-catalysed autoxidation. Isolated rat hearts, perfused with non-chelexed Krebs-Henseleit buffer plus 0.25 mM ascorbate for 60 min, sustained moderate injury with developed systolic pressure, +dP/dtmax and -dP/dtmax decreased by 30 to 35% by the end of experiment. Hearts perfused with chelating resin-treated Krebs-Henseleit buffer sustained no significant injury within the same time frame. Furthermore, it was observed that hearts perfused with non-chelexed Krebs-Henseleit buffer accumulate significant amounts of copper depending on the amount of contamination and length of perfusion. Significant effects on post-ischemic end diastolic pressure were observed in hearts perfused with a Krebs-Henseleit buffer subsequently found to be contaminated with high levels of copper. These results clearly demonstrate that adventitious redox-active transition metals may be a confounding factor in experimental results. Further, it is recommended that all perfusion media be routinely examined for adventitious metals and treated if deemed necessary.
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PMID:Adventitious redox-active metals in Krebs-Henseleit buffer can contribute to Langendorff heart experimental results. 852 67

Pyrococcus furiosus is a strictly anaerobic archaeon (archaebacterium) that grows at temperatures up to 105 degrees C by fermenting carbohydrates and peptides. Cell extracts have been previously shown to contain an unusual acetyl coenzyme A (acetyl-CoA) synthetase (ACS) which catalyzes the formation of acetate and ATP from acetyl-CoA by using ADP and phosphate rather than AMP and PPi. We show here that P. furiosus contains two distinct isoenzymes of ACS, and both have been purified. One, termed ACS I, uses acetyl-CoA and isobutyryl-CoA but not indoleacetyl-CoA or phenylacetyl-CoA as substrates, while the other, ACS II, utilizes all four CoA derivatives. Succinyl-CoA did not serve as a substrate for either enzyme. ACS I and ACS II have similar molecular masses (approximately 140 kDa), and both appear to be heterotetramers (alpha2beta2) of two different subunits of 45 (alpha) and 23 (beta) kDa. They lack metal ions such as Fe2+, Cu2+, Zn2+, and Mg2+ and are stable to oxygen. At 25 degrees C, both enzymes were virtually inactive and exhibited optimal activities above 90 degrees C (at pH 8.0) and at pH 9.0 (at 80 degrees C). The times required to lose 50% of their activity at 80 degrees C were about 18 h for ACS I and 8 h for ACS II. With both enzymes in the acid formation reactions, ADP and phosphate could be replaced by GDP and phosphate but not by CDP and phosphate or by AMP and PPi. The apparent Km values for ADP, GDP, and phosphate were approximately 150, 132, and 396 microM, respectively, for ACS I (using acetyl-CoA) and 61, 236, and 580 microM, respectively, for ACS II (using indoleacetyl-CoA). With ADP and phosphate as substrates, the apparent Km values for acetyl-CoA and isobutyryl-CoA were 25 and 29 microM, respectively, for ACS I and 26 and 12 microM, respectively, for ACS II. With ACS II, the apparent Km value for phenylacetyl-CoA was 4 microM. Both enzymes also catalyzed the reverse reaction, the ATP-dependent formation of the CoA derivatives of acetate (I and II), isobutyrate (I and II), phenylacetate (II only), and indoleacetate (II only). The N-terminal amino acid sequences of the two subunits of ACS I were similar to those of ACS II and to that of a hypothetical 67-kDa protein from Escherichia coli but showed no similarity to mesophilic ACS-type enzymes. To our knowledge, ACS I and II are the first ATP-utilizing enzymes to be purified from a hyperthermophile, and ACS II is the first enzyme of the ACS type to utilize aromatic CoA derivatives.
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PMID:Purification and characterization of two reversible and ADP-dependent acetyl coenzyme A synthetases from the hyperthermophilic archaeon Pyrococcus furiosus. 883 Jun 84

The bifunctional CO dehydrogenase/acetyl-CoA synthase (CODH/ACS) plays a central role in the Wood-Ljungdahl pathway of autotrophic CO(2) fixation. A recent structure of the Moorella thermoacetica enzyme revealed that the ACS active site contains a [4Fe-4S] cluster bridged to a binuclear Cu-Ni site. Here, biochemical and x-ray absorption spectroscopic (XAS) evidence is presented that the copper ion at the M. thermoacetica ACS active site is essential. Depletion of copper correlates with reduction in ACS activity and in intensity of the "NiFeC" EPR signal without affecting either the activity or the EPR spectroscopic properties associated with CODH. In contrast, Zn content is negatively correlated with ACS activity without any apparent relationship to CODH activity. Cu is also found in the methanogenic CODH/ACS from Methanosarcina thermophila. XAS studies are consistent with a distorted Cu(I)-S(3) site in the fully active enzyme in solution. Cu extended x-ray absorption fine structure analysis indicates an average Cu-S bond length of 2.25 A and a metal neighbor at 2.65 A, consistent with the Cu-Ni distance observed in the crystal structure. XAS experiments in the presence of seleno-CoA reveal a Cu-S(3)Se environment with a 2.4-A Se-Cu bond, strongly implicating a Cu-SCoA intermediate in the mechanism of acetyl-CoA synthesis. These results indicate an essential and functional role for copper in the CODH/ACS from acetogenic and methanogenic organisms.
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PMID:Functional copper at the acetyl-CoA synthase active site. 1258 21

The structure of carbon monoxide dehydrogenase/acetyl-coenzyme A synthase (CODH/ACS), a central enzyme in the anaerobic metabolism of acetyl-coenzyme A (acetyl-CoA), has been solved to a resolution of 2.2A. The active-site metal cluster responsible for catalyzing acetyl C-C bond synthesis and cleavage, designated the A center, was identified as an Fe(4)S(4) iron sulfur cluster with one of its cysteine thiolates acting as a bridge to an adjacent binuclear metal site. Nickel was found at one position in the binuclear site and the other metal was indicated to be copper - a surprising result, implying a previously unrecognized role for copper. Details of the A center provided new insight into the unusual organometallic mechanism of acetyl C-C bond formation and cleavage, with substantial conformational changes indicated for binding of the large methylcorrinoid protein substrate, and a unique intramolecular channel acting to contain carbon monoxide within the protein and transfer it to the site needed for acetyl-CoA synthesis.
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PMID:Acetate C-C bond formation and decomposition in the anaerobic world: the structure of a central enzyme and its key active-site metal cluster. 1276 30

Models for the active site of the acetyl CoA synthase (ACS) were synthesized by attachment of Cu+ and Ni(0) to nickel diaminodithiolate (S2N2) and diamidodithiolate (S2N2') complexes. The Ni-Ni species form stable CO adducts, i.e., [{(CO)2Ni}{NiS2N2'}]2-, whereas the Cu-NiS2N2 and Cu-NiS2N2' models do not. These results provide supporting evidence for a biological role for reduced nickel in ACS.
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PMID:Structural analogues of the bimetallic reaction center in acetyl CoA synthase: a Ni--Ni model with bound CO. 1286 45

The metal binding affinity of an (N2S2)Ni bridging metallothiolate ligand (Zn2+ < Ni2+ < Cu+) gives precedent for the observed heterogeneity in ACS/CODH.
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PMID:Capture of Ni(II), Cu(I) and Z(II) by thiolate sulfurs of an N2S2Ni complex: a role for a metallothiolate ligand in the acetyl-coenzyme A synthase active site. 1293 85

The nickel(II) complex of an N2S2 ligand, derived from a diazacycle, N,N'-bis(mercaptoethyl)-1,5-diazacycloheptane, (bme-dach)Ni, Ni-1', serves as a metallodithiolate ligand to NiII, CuI, ZnII, Ag, and PbII. The binding ability of the NiN2S2 ligand to the metal ions was established through spectrochemical titrations in aqueous media and compared to classical S-donor ligands. For M = Ni, Zn, Pb, binding constants, log K = ca. 2. were computed for 1:1 Ni-1'/M(solvate) adducts; for Ag+ and Cu+, the 3:2 (Ni-1')3M2 adducts were the first formed products even in water with log beta3,2 values of 26 and >30, respectively. In all cases, the binding ability of Ni-S-R is intermediate between that of a free thiolate and a free thioether. The great specificity for copper over nickel and zinc by N2S2Ni, which serves as a reasonable structural model for the distal nickel of the acetyl CoA synthase active site, relates to biochemical studies of heterogeneity (metal content and type) in various preparations of acetyl CoA synthase enzyme.
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PMID:N2S2Ni metallodithiolate complexes as ligands: structural and aqueous solution quantitative studies of the ability of metal ions to form M-S-Ni bridges to mercapto groups coordinated to nickel(II). implications for acetyl coenzyme A synthase. 1585 64

Oxidized low-density lipoprotein (oxLDL) is immunogenic while oxidized phospholipids (oxPL) formed on oxLDL and lysophosphatidylcholine (lyso-PC) generated during LDL oxidation through the hydrolysis of oxPL by the lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), significantly contribute to oxLDL immunogenicity. We determined the autoantibody titers against various forms of mildly oxLDL in patients with acute coronary syndromes without persistent elevation of the ST segment (NSTE-ACS) and with undetectable serum levels of lipoprotein (a). Moreover, the effect of early atorvastatin administration on these autoantibody titers was evaluated. From the 133 consecutive NSTE-ACS patients, 55 were eligible for the study. Thirty-four received atorvastatin (group A), whereas 21 did not received any hypolipidemic therapy (group B). Two forms of copper-oxidized LDL were prepared at the end of propagation or decomposition phase (oxLDL(P) or oxLDL(D), respectively). Similar types of oxLDL were prepared after previous inactivation of the endogenous Lp-PLA(2) [oxLDL(-)]. In group B, autoantibody titers of IgG class against oxLDL(P) and oxLDL(D) were elevated at 1 month of follow-up to reach the baseline values 3 months afterwards. By contrast the titers against oxLDL(-)(P) and oxLDL(-)(D) increased at 1 month of follow-up and remained elevated for up to 6 months of follow-up. Atorvastatin treatment prevented the elevation of autoantibody titers against all forms of oxidized LDL. We conclude that a short-term immune response against oxLDL(P) and oxLDL(D) (enriched in lyso-PC) and a chronic immune response against oxLDL(-)(P) and oxLDL(-)(D) (enriched in oxPL) are observed after an NSTE-ACS, suggesting an important role of the LDL-associated Lp-PLA(2) in modulating these immune responses. Early atorvastatin treatment prevents both immune responses; however, the clinical significance of this effect remains to be established.
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PMID:Short- and long-term elevation of autoantibody titers against oxidized LDL in patients with acute coronary syndromes. Role of the lipoprotein-associated phospholipase A2 and the effect of atorvastatin treatment. 1714 May 82

After activation with NiCl2, the recombinant alpha subunit of the Ni-containing alpha2beta2 acetyl-CoA synthase/carbon monoxide dehydrogenase (ACS/CODH) catalyzes the synthesis of acetyl-CoA from CO, CoA, and a methyl group donated from the corrinoid-iron-sulfur protein (CoFeSP). The alpha subunit has two conformations (open and closed), and contains a novel [Fe4S4]-[Nip Nid] active site in which the proximal Nip ion is labile. Prior to Ni activation, recombinant apo-alpha contain only an Fe4S4 cluster. Ni-activated alpha subunits exhibit catalytic, spectroscopic and heterogeneity properties typical of alpha subunits contained in ACS/CODH. Evidence presented here indicates that apo-alpha is a monomer whereas Ni-treated alpha oligomerizes, forming dimers and higher molecular weight species including tetramers. No oligomerization occurred when apo-alpha was treated with Cu(II), Zn(II), or Co(II) ions, but oligomerization occurred when apo-alpha was treated with Pt(II) and Pd(II) ions. The dimer accepted only 0.5 methyl group/alpha and exhibited, upon treatment with CO and under reducing conditions, the NiFeC EPR signal quantifying to 0.4 spin/alpha. Dimers appear to consist of two types of alpha subunits, including one responsible for catalytic activity and one that provides a structural scaffold. Higher molecular weight species may be similarly constituted. It is concluded that Ni binding to the A-cluster induces a conformational change in the alpha subunit, possibly to the open conformation, that promotes oligomerization. These interrelated events demonstrate previously unrealized connections between (a) the conformation of the alpha subunit; (b) the metal which occupies the proximal/distal sites of the A-cluster; and (c) catalytic activity.
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PMID:Nickel-dependent oligomerization of the alpha subunit of acetyl-coenzyme a synthase/carbon monoxide dehydrogenase. 1788 77

Donnan dialysis is an ion exchange membrane process that can be used for the purification and concentration of diluted solutions. In this work, the behaviour of gold, silver and copper in cyanide medium is examined. Flux of cyanide complexes and corresponding free cyanide are determined using five commercial anion exchanger membranes (AMV, ACS, RAI 5035, ADP and ADS). The results show that the rate transfer depends upon the nature of the anion exchanger membrane. It is observed that the species number in the feed solution influences the transfer selectivity of metal ion complex against free cyanide Thus, gold which forms only one stable species with cyanides is transferred faster through an ACS membrane than copper which forms three species. However, this result is not verified when an ADS membrane is used. A model of the complex transfer through anion exchange membranes based on Donnan dialysis is proposed. A three compartment Donnan dialysis is performed to improve the separation between the studied metals. Decyanidation is also examined and separation factors are calculated. It is shown that Donnan dialysis can be an efficient technique for the separation of cyanides complexes of copper, gold and silver when parameters such as anion exchange membrane and the number of compartments are optimised. An advantage of this technique is also the possibility of recycling all reactants with a good impact on the environment.
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PMID:Donnan dialysis of copper, gold and silver cyanides with various anion exchange membranes. 1896 59


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