A spectrophotometric determination of cyanate using reaction with 2-aminobenzoic acid

Guilloton, Michel; Karst, Francis

doi:10.1016/0003-2697(85)90572-x

Cited by 46 publications

(40 citation statements)

References 14 publications

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“…The peak absorbance of this dye is followed spectrophotometrically at 585 nm (ε max = 131600 M −1 cm −1 ). The concentration of cyanate was determined spectrophotometrically employing a modified method of Guilloton and Karst based on the reaction between cyanate ions and 2-aminobenzoic acid under buffered conditions [26]. The concentration of cyanate could be precisely determined independently of the pH of the system, and in the presence of cyanide ions, by measuring the absorbance of the complex formed at 310 nm.…”

Section: Methods and Apparatusmentioning

confidence: 99%

Novel Ni−Fe-oxide systems for catalytic oxidation of cyanide in an aqueous phase

Stoyanova

Christoskova

2005

Open Chemistry

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Catalytic activity of mixed Ni-Fe oxide systems with respect to air oxidation of aqueous cyanide solution at 308 K was investigated. The catalysts employed were prepared by an oxidation-precipitation method at room temperature and were characterized by powder Xray diffraction (XRD), Mössbauer spectroscopy, and chemical analysis. The cyanide oxidation rate was found to be dependent on the catalyst's calcination temperature, pH of the medium, and catalyst loading. Results revealed that the catalyst calcined at 120 • C is the most active where up to 90 % of free cyanide (4 mM) was removed after oxidation for 30 minutes in the presence of 2.5 g/L catalyst at pH 9.5. The cyanide conversion becomes less favorable as the pH of the solution increases (with other constant parameters). The selectivity data showed that carbon dioxide is the main oxidation product, regardless of pH of the solution.

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Section: Methods and Apparatusmentioning

confidence: 99%

Novel Ni−Fe-oxide systems for catalytic oxidation of cyanide in an aqueous phase

Stoyanova

Christoskova

2005

Open Chemistry

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“…Cultures which did not exhibit a normal growth rate were discarded, and only those with a generation time of about 50 min, which corresponds to the noninhibited growth, were used. Cyanate decomposition in vivo was measured as described previously (8).…”

Section: Methodsmentioning

confidence: 99%

Role of bicarbonate/CO2 in the inhibition of Escherichia coli growth by cyanate

et al. 1995

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Cyanase is an inducible enzyme in Escherichia coli that catalyzes the reaction of cyanate with bicarbonate to give two CO 2 molecules. The gene for cyanase is part of the cyn operon, which includes cynT and cynS, encoding carbonic anhydrase and cyanase, respectively. Carbonic anhydrase functions to prevent depletion of cellular bicarbonate during cyanate decomposition (the product CO 2 can diffuse out of the cell faster than noncatalyzed hydration back to bicarbonate). Addition of cyanate to the culture medium of a ⌬cynT mutant strain of E. coli (having a nonfunctional carbonic anhydrase) results in depletion of cellular bicarbonate, which leads to inhibition of growth and an inability to catalyze cyanate degradation. These effects can be overcome by aeration with a higher partial CO 2 pressure (M. B. Guilloton, A. F. Lamblin, E. I. Kozliak, M. Gerami-Nejad, C. Tu, D. Silverman, P. M. Anderson, and J. A. Fuchs, J. Bacteriol. 175:1443-1451, 1993). The question considered here is why depletion of bicarbonate/CO 2 due to the action of cyanase on cyanate in a ⌬cynT strain has such an inhibitory effect. Growth of wild-type E. coli in minimal medium under conditions of limited CO 2 was severely inhibited, and this inhibition could be overcome by adding certain Krebs cycle intermediates, indicating that one consequence of limiting CO 2 is inhibition of carboxylation reactions. However, supplementation of the growth medium with metabolites whose syntheses are known to depend on a carboxylation reaction was not effective in overcoming inhibition related to the bicarbonate deficiency induced in the ⌬cynT strain by addition of cyanate. Similar results were obtained with a ⌬cyn strain (since cyanase is absent, this strain does not develop a bicarbonate deficiency when cyanate is added); however, as with the ⌬cynT strain, a higher partial CO 2 pressure in the aerating gas or expression of carbonic anhydrase activity (which contributes to a higher intracellular concentration of bicarbonate/CO 2 ) significantly reduced inhibition of growth. There appears to be competition between cyanate and bicarbonate/CO 2 at some unknown but very important site such that cyanate binding inhibits growth. These results suggest that bicarbonate/CO 2 plays a significant role in the growth of E. coli other than simply as a substrate for carboxylation reactions and that strains with mutations in the cyn operon provide a unique model system for studying aspects of the metabolism of bicarbonate/CO 2 and its regulation in bacteria.Cyanase (EC 4.3.99.1) catalyzes the reaction of cyanate with bicarbonate to give two molecules CO 2 (15):The synthesis of cyanase in Escherichia coli is induced by addition of cyanate to the growth medium (2). The gene for cyanase is part of the cyn operon, which includes three genes in the order cynT, cynS, and cynX, encoding carbonic anhydrase, cyanase, and a hydrophobic protein of unknown function, respectively (11,(30)(31)(32)(33). The function of carbonic anhydrase appears to be to prevent depletion of cellular bicarb...

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“…Spectrophotometric determination of cyanate was done according to Guilloton & Karst (1985). Assay of cyanase.…”

Section: Methodsmentioning

confidence: 99%

Isolation and Characterization of Escherichia coli Mutants Lacking Inducible Cyanase

Guilloton

Karst

1987

Microbiology

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To determine the physiological role of cyanate aminohydrolase (cyanase, EC 3.5.5.3) in bacteria, mutants of Escherichia coli K12 devoid of this inducible activity were isolated and their properties investigated. Five independent mutations were localized next to lac; three of them lay beween lacy and codA. Thus cyanase activity could depend on the integrity of one gene or set of clustered genes; we propose for this locus the symbol cnt. Growth of the mutant strains was more sensitive to cyanate than growth of wild-type strains. This difference was noticeable in synthetic medium in the presence of low concentrations of cyanate (< 1 mM). Higher concentrations inhibited growth of both wild-type and mutant strains. Urea in aqueous solutions dissociates slowly into ammonium cyanate. Accordingly wild-type strains were able to grow on a synthetic medium containing 0.5 M-urea whereas mutants lacking cyanase were not. We conclude that cyanase could play a role in destroying exogenous cyanate originating from the dissociation of carbamoyl compounds such as urea ; alternatively cyanate might constitute a convenient nitrogen source for bacteria able to synthesize cyanase in an inducible way.

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A spectrophotometric determination of cyanate using reaction with 2-aminobenzoic acid

Cited by 46 publications

References 14 publications

Novel Ni−Fe-oxide systems for catalytic oxidation of cyanide in an aqueous phase

Novel Ni−Fe-oxide systems for catalytic oxidation of cyanide in an aqueous phase

Role of bicarbonate/CO2 in the inhibition of Escherichia coli growth by cyanate

Isolation and Characterization of Escherichia coli Mutants Lacking Inducible Cyanase

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