A New Spectrophotometric Method for the Determination of Small Amounts of Chloride Using the Mercuric Thiocyanate Method

Iwasaki, Iwaji; Utsumi, Satori; Hagino, Ken; Ozawa, T.

doi:10.1246/bcsj.29.860

Cited by 172 publications

(60 citation statements)

References 6 publications

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“…The filtered sample water was analyzed value and the average concentration in seawater, for chloride and sulfate by the colorimetric respectively. methods of, respectively, Iwasaki et al (1956) The deposition rates of sodium vary widely and Iwasaki et al (1957), and for sodium and with place and season (Fig. 1).…”

Section: Resultsmentioning

confidence: 99%

Deposition of anthropogenic sulfate and Pb-210 in the western North Pacific area.

1985

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The monthly deposition rates of sodium, calcium, chloride, sulfate and Pb-210 from the atmosphere were measured at 12 stations in various parts of the Japanese Islands for two years. The deposition rates of sea salt particles were higher in the coastal region near the Sea of Japan in winter, demonstrating the fact that the strong winter monsoon produces many sea salt particles. Amounts of chloride, sulfate and calcium in excess of the sea salt component were always observed. The rather uniform annual deposition rates of excess sulfate (3-10g/m2/y) suggest that a large part of this excess sulfate originates in global air pollution. Pb-210, much of which is of upper atmospheric origin, is also deposited in significant amounts in winter . This seasonal change may be due to the replacement of lower air masses over the continental margin area , which yields a two-layer model for the atmospheric transport of chemical constituents. The geographical variation of Pb-210 deposition can be explained using the two-layer model and by assuming a 12 day residence time for the tropospheric aerosols. The deposition rates for sulfate over the ocean area decrease more rapidly with distance from the continental coast than those for Pb-210. This result may show that the atmospheric residence time of sulfate is shorter than that of Pb-210.

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Section: Resultsmentioning

confidence: 99%

Deposition of anthropogenic sulfate and Pb-210 in the western North Pacific area.

1985

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“…The reaction was terminated by addition of 0.1 volume of 3 N H 2 SO 4 . Chloride ions released were determined spectrophotometrically with mercuric thiocyanate and ferric ammonium sulfate (5). One unit of enzyme activity was defined as the amount of enzyme that catalyzes dehalogenation of 1 mol of L-CPA per min.…”

Section: Methodsmentioning

confidence: 99%

Bacterial DL-2-haloacid dehalogenase from Pseudomonas sp. strain 113: gene cloning and structural comparison with D- and L-2-haloacid dehalogenases

et al. 1997

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DL-2-Haloacid dehalogenase from Pseudomonas sp. strain 113 (DL-DEX) catalyzes the hydrolytic dehalogenation of both D-and L-2-haloalkanoic acids to produce the corresponding L-and D-2-hydroxyalkanoic acids, respectively, with inversion of the C 2 configuration. DL-DEX is a unique enzyme: it acts on the chiral carbon of the substrate and uses both enantiomers as equivalent substrates. We have isolated and sequenced the gene encoding DL-DEX. The open reading frame consists of 921 bp corresponding to 307 amino acid residues. No sequence similarity between DL-DEX and L-2-haloacid dehalogenases was found. However, DL-DEX had significant sequence similarity with D-2-haloacid dehalogenase from Pseudomonas putida AJ1, which specifically acts on D-2-haloalkanoic acids: 23% of the total amino acid residues of DL-DEX are conserved. We mutated each of the 26 residues with charged and polar side chains, which are conserved between DL-DEX and D-2-haloacid dehalogenase. Thr65, Glu69, and Asp194 were found to be essential for dehalogenation of not only the D-but also the L-enantiomer of 2-haloalkanoic acids. Each of the mutant enzymes, whose activities were lower than that of the wild-type enzyme, acted on both enantiomers of 2-haloacids as equivalent substrates in the same manner as the wild-type enzyme. We also found that each enantiomer of 2-chloropropionate competitively inhibits the enzymatic dehalogenation of the other. These results suggest that DL-DEX has a single and common catalytic site for both enantiomers.DL-2-Haloacid dehalogenase from Pseudomonas sp. strain 113 (DL-DEX) catalyzes the hydrolytic dehalogenation of both enantiomers of 2-haloalkanoic acids to produce the corresponding 2-hydroxyalkanoic acids with inversion of the C 2 configuration (14, 15). DL-DEX is a unique enzyme; it acts on the chiral carbon of the substrate enantiomers, which are used as equivalent substrates. Most other enzymes acting on the chiral carbon of substrates act on a sole enantiomer. Racemases and DL-DEX are the exceptions, although racemases differ markedly from DL-DEX in that they catalyze stereochemical but not chemical conversion of substrates. Racemases are believed to possess a single and common binding site for both substrate enantiomers. Thus, it will be interesting to clarify whether DL-DEX has a common site or distinct ones for each enantiomer in order to compare it with racemases. Different kinds of 2-haloacid dehalogenases showing different stereospecificities have been isolated from several bacterial strains (2, 6, 21). L-2-Haloacid dehalogenases specifically act on L-enantiomers of 2-haloacids to produce the corresponding D-2-hydroxy acids (11, 13, 23). D-2-Haloacid dehalogenase from Pseudomonas putida AJ1 dehalogenates D-enantiomers to form L-2-hydroxy acids (22). Although the two families of dehalogenases act on opposite enantiomers of 2-haloacids, they are similar to each other in that they act exclusively on one particular enantiomer. Thus, DL-DEX differs markedly from them in this respect, although all of them deha...

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“…The chloride ions released were measured spectrophotometrically (21). One unit of enzyme was defined as the amount of the enzyme that catalyzes the dehalogenation of 1 mol of the substrate/min.…”

Section: Reaction Mechanism Of Dl-2-haloacid Dehalogenase 20978mentioning

confidence: 99%

dl-2-Haloacid Dehalogenase fromPseudomonas sp. 113 Is a New Class of Dehalogenase Catalyzing Hydrolytic Dehalogenation Not Involving Enzyme-Substrate Ester Intermediate

Nardi‐Dei¹,

Kurihara²,

Park³

et al. 1999

Journal of Biological Chemistry

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18 O of the solvent directly attacks the ␣-carbon of 2-haloalkanoic acid to displace the halogen atom. This is the first example of an enzymatic hydrolytic dehalogenation that proceeds without producing an ester intermediate.Various enzymes catalyzing hydrolytic dehalogenation of organohalogen compounds have been isolated and characterized (1-3). These enzymes include 2-haloacid dehalogenases (EC 3.8.1.2), haloacetate dehalogenases (EC 3.8.1.3), haloalkane dehalogenases (EC 3.8.1.5), and 4-chlorobenzoyl-CoA dehalogenases (EC 3.8.1.6). 2-Haloacid dehalogenases are further classified into three groups based on their substrate specificities (4). L-2-Haloacid dehalogenase (L-DEX) 1 specifically acts on L-2-haloalkanoic acids, and the corresponding D-2-hydroxyalkanoic acids are produced. D-2-Haloacid dehalogenase (D-DEX) catalyzes the conversion of D-2-hydroxyalkanoic acids into L-2-hydroxyalkanoic acids. DL-2-Haloacid dehalogenase (DL-DEX) dehalogenates both D-and L-2-haloalkanoic acids, and the corresponding L-and D-2-hydroxyalkanoic acids are produced. DL-DEX is similar to racemases and epimerases in that it acts indiscriminately on the chiral center of both D-and L-enantiomers. However, this enzyme is unique in that it catalyzes a chemical conversion on the chiral centers of both enantiomers. Thus far, the reaction mechanisms of L-DEX from Pseudomonas sp. YL (L-DEX YL) (5-7), haloalkane dehalogenase from Xanthobacter autotrophicus GJ10 (8 -10), and 4-chlorobenzoylCoA dehalogenases from Pseudomonas sp. strain CBS3 (11,12) and Arthrobacter sp. 4-CB1 (13) have been analyzed. Their reactions proceed as shown in Fig. 1A. Each of these dehalogenases has an acidic amino acid residue whose carboxylate group attacks the carbon atom of the substrate to which the halogen atom is bound. Asp 10 of L-DEX YL, Asp 124 of haloalkane dehalogenase from X. autotrophicus GJ10, and Asp 145 of 4-chlorobenzoyl-CoA dehalogenase from Pseudomonas sp. strain CBS3 were identified to play this essential role for respective enzymes. The ester intermediates produced in the course of these reactions are subsequently hydrolyzed releasing the products and restoring the carboxylate groups of the enzymes. These were confirmed by chemical modification, sitedirected mutagenesis, mass spectrometry, and x-ray crystallographical analysis (5-13).DL-DEXs have been purified from Pseudomonas sp. 113 (DL-DEX 113) (14), Pseudomonas putida PP3 (15), and Rhizobium sp. (16). However, none of the reaction mechanisms of these DL-DEXs have been studied, and it is unknown whether the reaction mechanism of DL-DEX is similar to that of other halidohydrolases (dehalogenases that catalyze the hydrolytic dehalogenation). We previously determined the primary structure of DL-DEX 113 (Fig. 2), and found that it is similar to that of D-DEX from Pseudomonas putida AJ1 (17). We also showed that DL-DEX 113 has a single and common catalytic site for both D-and L-enantiomers based on a site-directed mutagenesis experiment and kinetic analysis (17). In the present study, we analyze...

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A New Spectrophotometric Method for the Determination of Small Amounts of Chloride Using the Mercuric Thiocyanate Method

Cited by 172 publications

References 6 publications

Deposition of anthropogenic sulfate and Pb-210 in the western North Pacific area.

Deposition of anthropogenic sulfate and Pb-210 in the western North Pacific area.

Bacterial DL-2-haloacid dehalogenase from Pseudomonas sp. strain 113: gene cloning and structural comparison with D- and L-2-haloacid dehalogenases

dl-2-Haloacid Dehalogenase fromPseudomonas sp. 113 Is a New Class of Dehalogenase Catalyzing Hydrolytic Dehalogenation Not Involving Enzyme-Substrate Ester Intermediate

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