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At least 19 recordsLinked to original sources
PubMed2006

Three autocatalysts and self-inhibition in a single reaction: a detailed mechanism of the chlorite-tetrathionate reaction.

The chlorite-tetrathionate reaction has been studied spectrophotometrically in the pH range of 4.65-5.35 at T = 25.0 +/- 0.2 degrees C with an ionic strength of 0.5 M, adjusted with sodium acetate as a buffer component. The reaction is unique in that it demonstrates autocatalysis with respect to the hydrogen and chloride ion products and the key intermediate, HOCl. The thermodynamically most-favorable stoichiometry, 2S(4)O(6)2- + 7ClO2- + 6H2O --> 8SO(4)2- + 7Cl- + 12H+, is not found. Under our experimental conditions, chlorine dioxide, the chlorate ion, or both are detected in appreciable amounts among the products. Initial rate studies reveal that the formation of chlorine dioxide varies in an unusual way, with the chlorite ion acting as a self-inhibitor. The reaction is supercatalytic (i.e., second order with respect to autocatalyst H+). The autocatalytic behavior with respect to Cl- comes from chloride catalysis of the chlorite-hypochlorous acid and hypochlorous acid-tetrathionate subsystems. A detailed kinetic study and a model that explains this unusual kinetic behavior are presented.

Journal Article↗
PubMed1986

[Comparative study of the detection of Pseudomonas aeruginosa in water].

In this report we examined quantitatively (MPN-procedure) various methods of isolating Ps. aeruginosa from surface waters. When comparing different media (malachitgreen broth, Preuss-broth, selenite broth, asparagine broth, malachitgreen/acetamide broth) the enrichments in malachitgreen and asparagine showed the highest isolation frequencies after an 48 h incubation time. In heavily polluted river water the results can be improved by a second enrichment step in acetamide broth. Dependent on the river water pollution 0...11,000 Ps. aeruginosa/l were detected. In waste water up to 2.4 X 10(6) Ps. aeruginosa/l were isolated. The results emphasize the significance of water as a reservoir and a source of distribution of Ps. aeruginosa in the environment.

Acetamides↗
PubMed2004

Localization, purification and properties of a tetrathionate hydrolase from Acidithiobacillus caldus.

The moderately thermophilic bacterium Acidithiobacillus caldus is found in bacterial populations in many bioleaching operations throughout the world. This bacterium oxidizes elemental sulfur and other reduced inorganic sulfur compounds as the sole source of energy. The purpose of this study was to purify and characterize the tetrathionate hydrolase of A. caldus. The enzyme was purified 16.7-fold by one step chromatography using a SP Sepharose column. The purified enzyme resolved into a single band in 10% polyacrylamide gel, both under denaturing and native conditions. Its homogeneity was confirmed by N-terminal amino acid sequencing. Tetrathionate hydrolase was shown to be a homodimer with a molecular mass of 103 kDa (composed from two 52 kDa monomers). The purified enzyme had optimum activity at pH 3.0 and 40 degrees C and an isoelectric point of 9.8. The periplasmic localization of the enzyme was determined by differential fractionation of A. caldus cells. Detected products of the tetrathionate hydrolase reaction were thiosulfate and pentathionate as confirmed by RP-HPLC analysis. The activity of the purified enzyme was drastically enhanced by divalent metal ions.

Acidithiobacillus↗
PubMed2000

Isolation and characterization of alkaliphilic, chemolithoautotrophic, sulphur-oxidizing bacteria.

Alkaliphilic sulphur-oxidizing bacteria were isolated from samples from alkaline environments including soda soil and soda lakes. Two isolates, currently known as strains AL 2 and AL 3, were characterized. They grew over a pH range 8.0-10.4 with an optimum at 9.5-9.8. Both strains could oxidize thiosulphate, sulphide, polysulphide, elemental sulphur and tetrathionate. Strain AL 3 more actively oxidized thiosulphate and sulphide, while isolate AL 2 had higher activity with elemental sulphur and tetrathionate. Isolate AL 2 was also able to oxidize trithionate. The pH optimum for thiosulphate and sulphide oxidation was between 9-10. Some activity remained at pH 11, but was negligible at pH 7. Metabolism of tetrathionate by isolate AL 2 involved initial anaerobic hydrolysis to form sulphur, thiosulphate and sulphate in a sequence similar to that in other colourless sulphur-oxidizing bacteria. Sulphate was produced by both strains. During batch growth on thiosulphate, elemental sulphur and sulphite transiently accumulated in cultures of isolates AL 2 and AL 3, respectively. At lower pH values, both strains accumulated sulphur during sulphide and thiosulphate oxidation. Both strains contained ribulose bisphosphate carboxylase. Thiosulphate oxidation in isolate AL 3 appeared to be sodium ion-dependent. Isolate AL 2 differed from AL 3 by its high GC mol % value (65.5 and 49.5, respectively), sulphur deposition in its periplasm, the absence of carboxysomes, lower sulphur-oxidizing capacity, growth kinetics (lower growth rate and higher growth yield) and cytochrome composition.

Anaerobiosis↗
PubMed2005

Paracoccus bengalensis sp. nov., a novel sulfur-oxidizing chemolithoautotroph from the rhizospheric soil of an Indian tropical leguminous plant.

Paracoccus versutus-like isolates from the rhizosphere of Clitoria ternatea, a slender leguminous herb (family--Papilionaceae), found ubiquitously in waste places and village forests of the Lower Gangetic plains of India, presented a case of graduated infraspecific variation that was capped by the identification of a new species Paracoccus bengalensis (type strain JJJ(T) = LMG 22700(T) = MTCC 7003(T)). The diverged phenetic and genetic structure of these sulfur-oxidizing chemolithoautotrophs presented a case of apparent nonconformity of 16S rRNA gene sequence similarities with results of DNA-DNA hybridization. Despite high 16S rRNA gene sequence similarity with P. versutus one of the newly isolated strains, viz., JJJ(T) was identified as a new species of Paracoccus by virtue of its explicitly low DNA-DNA hybridization (42-45%) with the type strain of the closest species P. versutus (), distinct G + C content (65.3 mol%), physiological and biochemical differences amounting to <60% phenetic similarity with strains of P. versutus as well as new isolates akin to the species. The newly described species also had a unique fatty acid profile that was distinguished by the absence of 18:1 omega9c, unique possession of Summed feature 3 (16:1omega7c & 15:0 iso 2-OH), 19:0 10 methyl, and a much higher concentration of 19:0 cycloomega8c.

Fabaceae↗
PubMed2004

Phylogenetically diverse new sulfur chemolithotrophs of alpha-proteobacteria isolated from Indian soils.

Five facultative sulfur chemolithotrophs were isolated from soils to study the diversity of sulfur lithotrophy. Phenotypic characteristics, including sulfur lithotrophic properties and chemotaxonomic features of the isolates, were similar to those of the members of the colorless sulfur bacteria. 16S rDNA sequence analyses rendered placing the isolates to three distinct phylogenetic clusters of alpha-proteobacteria. Three isolates, AS001, AS002, and KCT002, were identified as members of the genus Paracoccus. The strains AS001 and AS002, having identical 16S-rDNA sequence, showed significant 16S rDNA sequence similarity (99.1%) to Paracoccus versutus. The strain KCT002 showed highest (98%) 16S rDNA sequence similarity to P. alcaliphilus and 96% similarity to the pair AS001 and AS002. Isolate KCT001 appeared to be closely related to Pseudaminobacter salicylatoxidans, although sulfur lithotrophy of P. salicylotoxidans is not known. The other isolate, TCK, showed almost identical 16S rDNA (99.9%) sequence with two recently described unclassified chemolithoautotrophic arsenite oxidizing strains. Physiological and chemotaxonomic characteristics and phylogenetic analyses of the five new strains emphasize the need of polyphasic bacterial taxonomy of sulfur lithotrophs.

Alphaproteobacteria↗
PubMed1985

Purification of 2,3-bisphosphoglycerate synthase-phosphatase from pig skeletal muscle.

Two enzymes which possess 2,3-bisphosphoglycerate synthase, 2,3-bisphosphoglycerate phosphatase and phosphoglycerate mutase activities have been purified from pig skeletal muscle. One of the enzymes corresponds to type M phosphoglycerate mutase. The other enzyme shows properties similar to those of the 2,3-bisphosphoglycerate synthase-phosphatase present in mammalian erythrocytes. The erythrocyte and the muscle enzyme possess the same molecular (56 000) and subunit (27 000) weights. The synthase, phosphatase and mutase activity ratio is similar in both enzymes, and they are affected by the same inhibitor (glycerate 3-P) and activators (glycolate 2-P, pyrophosphate, sulfite and bisulfite).

Animals↗
PubMed1997

Cytoplasmic calcium buffers in intact human red cells.

1. Precise knowledge of the cytoplasmic Ca2+ buffering behaviour in intact human red cells is essential for the characterization of their [Ca2+]i-dependent functions. This was investigated by using a refined method and experimental protocols which allowed continuity in the estimates of [Ca2+]i, from nanomolar to millimolar concentrations, in the presence and absence of external Ca2+ chelators. 2. The study was carried out in human red cells whose plasma membrane Ca2+ pump was inhibited either by depleting the cells of ATP or by adding vanadate to the cell suspension. Cytoplasmic Ca2+ buffering was analysed from plots of total cell calcium content vs. ionized cytoplasmic Ca2+ concentration ([CaT]i vs. [Ca2+]i) obtained from measurements of the equilibrium distribution of 45Ca2+ at different external Ca2+ concentrations ([Ca2+]o), in conditions known to clamp cell volume and pH. The equilibrium distribution of 45Ca2+ was induced by the divalent cation ionophore A23187. 3. The results showed the following. (i) The known red cell Ca2+ buffer represented by alpha, with a large capacity and low Ca2+ affinity, was the main cytoplasmic Ca2+ binding agent. (ii) The value of alpha was remarkably constant; the means for each of four donors ranged from 0.33 to 0.35, with a combined value of all independent measurements of 0.34 +/- 0.01 (mean +/- S.E.M., n = 16). This contrasts with the variability previously reported. (iii) There was an additional Ca2+ buffering complex with a low capacity (approximately 80 micromol (340 g Hb)(-1)) and intermediate Ca2+ affinity (apparent dissociation constant, K(D,app) approximately 4-50 microM) whose possible identity is discussed. (iv) The cell content of putative Ca2+ buffers with submicromolar Ca2+ dissociation constants was below the detection limit of the methods used here (less than 2 micromol (340 g Hb)(-1)). 4. Vanadate (1 mM) inhibited the Vmax of the Ca2+ pump in inosine-fed cells by 99.7%. The cytoplasmic Ca2+ buffering behaviour in these cells was similar to that found in ATP-depleted cells.

Adenosine Triphosphate↗
PubMed1985

L1210 dihydrofolate reductase: activation and enhancement of methotrexate sensitivity.

Dihydrofolate reductase, purified to homogeneity from a subline of L1210 murine leukemia cells resistant to 10(-6) M Methotrexate, was resolved into two principal forms (1 and 2) by isoelectric focusing. These forms had pI values of 7.4 and 8.2, respectively; both stained for protein and catalytic activity. Form 1 was a single component, comprising ca. 10% of the total protein, but multiple components of 2 were observed by narrowing the pH range in the electrophoretic procedure. Urea-denatured enzyme exhibited two bands of approximately equal intensity upon isoelectric focusing. These results were interpreted to mean that the enzyme consists of a set of conformationally different forms, arising from two primary structures. Inhibition of the native enzyme by Methotrexate was polyphasic, and appreciable activity remained when the drug was present at an equimolar concentration. Various agents (KCl, H+, urea, and SH-modifiers), known to "activate" dihydrofolate reductases, produced a monophasic, stoichiometric inhibition. Activating agents appear to induce a more open (and labile) conformation of the enzyme. This leads to increased affinity for MTX accompanied, in some instances, by increased catalytic activity.

Animals↗
PubMed1985

Purification and preliminary characterization of phosphoglycerate mutase from Schizosaccharomyces pombe.

Phosphoglycerate mutase could be purified to over 95% homogeneity by a single step procedure involving elution from Cibacron Blue-Sepharose by a pulse of cofactor 2,3-bisphosphoglycerate. Although the enzyme has been isolated in only small quantities (c. 100 micrograms), gel filtration and sodium dodecylsulphate polyacrylamide gel electrophoresis indicated that it is monomeric with Mr approximately 23,000, an extremely low value for this enzyme. Preliminary investigations of the kinetic characteristics and the nature of important amino acid side chains have been undertaken.

Diacetyl↗
PubMed1985

Effect of the lactoperoxidase system on lipoprotein lipase activity and lipolysis in milk.

The lactoperoxidase/SCN-/H2O2 system (LPS) was found to inhibit lipoprotein lipase (LPL) in milk. Inhibition was related to the amount of SCN-/H2O2 added to milk. Lipolysis was unaltered until LPL activity was decreased to less than 40% of the original activity. When LPL was inhibited further, decreased lipolysis was observed. Purified LPL was also inhibited by LPS, at similar concentrations of SCN-/H2O2 as in milk. It was shown that non enzymically prepared OSCN- inhibited LPL at concentrations comparable to those produced by the LPS. Cysteine could eliminate the effect of LPS on LPL. The sulphydryl reagents dithiobisnitrobenzoic acid and Na tetrathionate had no effect on LPL activity.

Animals↗
PubMed1990

The effect of sodium tetrathionate on cyanide conversion to thiocyanate by enzymatic and non-enzymatic mechanisms.

Sodium tetrathionate has been proposed as a cyanide antidote despite its reported toxicology and inhibitory effect on rhodanese. We investigated the effect of tetrathionate and an analog, dithionite, on rhodanese activity because of their structural similarity to thiosulfate, a known sulfane sulfur donor for this enzyme. Rhodanese activity of guinea pig liver homogenate was assayed by measuring the formation of ferric thiocyanate complex at 460 nm. With thiosulfate as a substrate, the Km for rhodanese was 6.7 mM and the Vmax was 0.67 mumol thiocyanate min-1 mg-1 protein. The conversion of cyanide to thiocyanate by rhodanese was inhibited in the presence of tetrathionate at the millimolar concentration (e.g. 1 mM) range. Dithionite had a negligible effect on rhodanese activity. Neither thiosulfate (1-100 mM) nor dithionite produced significant amounts of thiocyanate from cyanide spontaneously (i.e. non-enzymatically). However, in the absence of rhodanese, tetrathionate (1.0, 10.0 and 100.0 mM) produced a dose-dependent increase in thiocyanate. These data suggest that tetrathionate detoxifies cyanide non-enzymatically, which may, in part, account for its antidotal effects.

Animals↗
PubMed1996

Association of poly(ADP-ribose) polymerase with nuclear subfractions catalyzed with sodium tetrathionate and hydrogene peroxide crosslinks.

Poly(ADP-ribose) polymerase (PARP) is a nuclear enzyme which catalyzes the transfer of ADP-ribose units from NAD+ to a variety of nuclear proteins under the stimulation of DNA strand break. To examine its role in DNA repair, we have been studying the interaction of PARP with other nuclear proteins using disulfide cross-linking, initiated by sodium tetrathionate (NaTT). Chinese Hamster Ovary (CHO) cells were extracted sequentially with Nonidet P40 (detergent), nucleases (DNase+RNase), and high salt (1.6 M NaCl) with and without the addition of a sulfhydryl reducing agent. The residual structures are referred to as the nuclear matrix, and are implicated in the organization of DNA repair and replication. Treatment of the cells with NaTT causes the crosslinking of PARP to the nuclear matrix. Activating PARP by pretreating the cells with H2O2 did not increase the cross-linking of PARP with the nuclear matrix, suggesting a lack of additional interaction of the enzyme with the nuclear matrix during DNA repair. Both NaTT and H2O2 induced crosslinks of PARP that were extractable with high salt. To shorten the procedure, these crosslinks were extracted from cells without nucleases and high salt treatment, using phosphate buffer. Using western blotting, these crosslinks appeared as a smear of high molecular weight species including a possible dimer of PARP at 230 kDa, which return to 116 kDa following reduction with beta-mercaptoethanol.

Animals↗