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Enzymatyczna degradacja związków chlorowcoorganicznych

Lewandowicz A.

Wiadomości Chemiczne

2001

[Z] 55, 9-10

883--911

Degradation of the halogenated organic compound poses ecological, sanitary, as well as synthetic, and other problems. Enzymatic degradation of these compounds seems to be a promising option. There are many natural sources of the chlorinated organic compounds, as well as those connected with human activity. The first source dominates. However, human production cannot be ignored, however, due to the considerable toxicity of the compounds produced and their dissemination. The mechanisms, by which enzymes called dehalogenases catalyze halogen-carbon bond breaking varies. Dehalogenases following different pathways were isolated from many microorganisms. Their substrates are usually involved in halorespiration processes, so dehalogenation is involved in carbon source and energy supply, as well. Moreover, cometabolic dehalogenation is possible. Dehalogenases are also present in mammals. For example, iodine dehalogenases (so called deiodinases) are necessary for thyroid hormones homeostasis. Hydrolytic dehalogenases are currently the most studied among all classes of dehalogenases. They include such unusual enzymes as 4-chlorobenzoil-CoA dehalogenase, which is capable of breaking chlorine - aromatic carbon bond under room temperature and neutral pH, and fluoroacetate dehalogenase, which cleaves the carbon-fluorine bond. For some of these enzymes three-dimensional structures are available now and mechanistic details have been studied. This contribution summarizes the present knowledge of enzymatic catalysis of this unusual chemical processes with special consideration on reaction mechanism of the best known hydrolytic dehalogenases.

SO2 Inducedliberation of halide anions from organics

Bronikowski T., Pasiuk-Bronikowska W., Ulejczyk M.

Archiwum Ochrony Środowiska

1999

Vol. 25, no. 2

9-16

To shed more light chemical transformations of pollutants in atmospheric waters, the interaction between sulphoxo radicals ( SO(-3), SO(-4), SO(-5)) and some halogenated organic compounds (1,2,4,5-tetrakis(trifluoromethyl)benzene, 2,4,5-trichlorophenol and 2,5-dichlorophenol) in the aqueous phase was studied. The radicals were generated in a laboratory reactor with a planar gas-liquid interface where the autoxidation of dissolved SO2(SO(2-3), HSO(-3)) took place. The following effects were found: distinct reduction in the rate of SO2 oxidation to SO(2-4)(conductometric method), transformations of the initially applied organic compounds (as shown by uv-spectra) and liberation of halide ions (ionic chromatography). Suggestions on the mechanism of the interaction were given.

Zmierzając do wyjaśnienia chemicznych przemian polutantów w wodach atmosferycznych, badano wzajemne oddziaływane rodników siarkotlenowych i niektórych halogenopochodnych związków organicznych (1,2,4,5-tetrakis(trifluorometylo)benzenu, 2,4,5-trichlorofenolu oraz 2,5-dichlorofenolu) w fazie wodnej. Rodniki te generowano w laboratoryjnym reaktorze z płaską powierzchnią gaz-ciecz, w którym prowadzono autooksydację rozpuszczonego SO2(SO(2-3), HSO(-3)). Stwierdzono znaczne obniżenie szybkości wytwarzania SO(2-4) w obecności badanych związków organicznych (pomiary konduktometryczne), przemiany tych związków w czasie eksperymentów (badania spektrofotometryczne) oraz uwalnianie jonów halogenkowych (analiza metodą chromatografii jonowej). Przedstawiono sugestie dotyczące mechanizmu obserwowanych oddziaływań.