Hydrocarbon detoxification

The marine environment acts as a sink for a large proportion of polyaromatic hydrocarbons (PAH) and these compounds have become a major area of interest in aquatic toxicology. Mixed function oxidases (MFO) are a class of microsomal enzymes involved in oxidative transformation, the primary biochemical process in hydrocarbon detoxification as well as mutagen-carcinogen activation (1,2). The reactions carried out by these enzymes are mediated by multiple forms of cytochrome P-450 which controls the substrate specificity of the system (3). One class of MFO, the aromatic hydrocarbon hydroxylases (AHH), has received considerable attention in relation to their role in hydrocarbon hydroxylation. AHH are found in various species of fish (4) and although limited data is available it appears that these enzymes may be present in a variety of aquatic animals (5,6,7,8). 

Ribbons DW, RW Eaton (1982) Chemical transformations of aromatic hydrocarbons that support the growth of microorganisms. In Biodegradation and detoxification of environmental pollutants (Ed AM Chakrabarty), pp. 59-84. CRC Press, Boca Raton. 

Methylphenanthrene fulfills the structural requirements but, as in the case of the other monomethylphenanthracenes, is inactive as a tumor initiator on mouse skin ( 5). This seems to be due to facile metabolic detoxification by formation of the 9,10-dihydrodiol, a process which is blocked in the tumorigenic isomers 1,4- and 4,10-dime thy lphenanthrene ( 5,j>). Among the methylated benzoicIphenan-threnes, the 3-,4-,5-, and 6-methyl isomers are the most tumori-genic The 1-methyl isomer, in which the methyl group is present in a 4-sided "fjord , is only weakly active like the parent hydrocarbon (23). 

Heitkamp, M.A. (1988) Environmental and biological factors affecting the biodegradation and detoxification of polycyclic aromatic hydrocarbons. Diss. Abstr. Int l. B. 48, 1926. 

Cemiglia, C.E., G.L. White, and R.H. Heflich. 1985. Fungal metabolism and detoxification of polycyclic aromatic hydrocarbons. Arch. Microbiol. 143 105-110. 

Like most halogenated hydrocarbon pesticides, very little of the chlordecone or its metabolites is excreted via the urine. Because of the apparent enterohepatic recirculation of chlordecone and chlordecone alcohol, most experimental approaches to chlordecone detoxification have focused on limiting reabsorption from the gastrointestinal tract using cholestyramine (Boylan et al. 1978 Cohn et al. 1978), liquid paraffin (Richter et al. 1979), and chlorella and chlorella- derived sporopollenin (Pore 1984). No information was found that indicated that mirex undergoes enterohepatic recirculation, so it is not known whether use of these therapies would be effective in reducing absorption of mirex. 

Together with glutathione conjugation, hydration is a major pathway in the inactivation and detoxification of arene oxides. Exceptions to this rule will be treated when discussing polycyclic aromatic hydrocarbons. Arene oxides are good substrates for microsomal EH, as evidenced in Table 10.1, where hydration of selected arene oxides, alkene oxides, and cy-cloalkene oxides by purified rat liver epoxide hydrolase is compared. The hy- ... 

The presence of benzo[6]thiophene in commercial naphthalene, its possible contamination with isomeric thienothiophenes 1 and 2, and their ability to poison aromatic hydrogenation catalysts led Maxted and Walker to develop detoxification by a preliminary short hydrogenation, in which thienothiophenes 1 and 2, and benzo[6]-thiophene are adsorbed on the catalyst. This is followed by their hydrogenation products that can easUy be oxidized with hydrogen peroxide or permolybdic acid to nontoxic sulfones subsequent hydrogenation of the aromatic hydrocarbons is then performed as usual. 

In 1948 Maxted and Walker studied the detoxification of catalyst poisons in the hydrogenation of aromatic hydrocarbons and found that the isomeric thienothiophenes 1 and 2 could be converted into the sul-fones of fully hydrogenated thienothiophenes 1 and 2, which do not poison the catalysts. This conversion is performed by brief preliminary hydrogenation and subsequent oxidation by hydrogen peroxide or per-molybdic acid. However, no data on the isolation or foe properties of these disulfones are available. It has been reported that direct oxidation of thienothiophenes 1 and 2 does not produce sulfones. 

Halide-saturated hydrocarbons such as carbon tetrachloride degrade very slowly, if at all, when exposed to solar detoxification treatment. Bicarbonate, a common constituent of groundwater, acts as a scavenger of hydroxyl radicals and can significantly hinder solar detoxification treatment. The presence of nontargeted contaminants in process infiuent can lower process efficiency. 

Cerniglia, C. E., Freeman, J. P., White, G. L., Heflich, R.H. Miller, D.W. (1985B). Fungal metabolism and detoxification of the nitropolycyclic aromatic hydrocarbon, 1-nitropyrene. Applied and Environmental Microbiology, 50, 649-... 

Sutherland, J. B. (1992). Detoxification of polycyclic aromatic hydrocarbons by fungi. Journal of Industrial Microbiology, 9, 53-62. 

Reductive dehalogenation of chlorinated phenols to phenol, cyclohexanol and other chlorine-free compounds takes place rapidly with hydrogen gas and Pd/C in an aqueous system or under solvent-free conditions. Thus, pentachloro phenol was able to be completely dechlorinated within 20 min (Scheme 4.45). This methodology enables a facile route for rapid and complete detoxification of highly toxic polychlorinated aromatic hydrocarbons and environmental remediation71,72. 

P16) (32,76)] hydrocarbons carcinogens, and detoxification metabolism. Arg554Lys polymorphism... 

Aryl hydrocarbon hydroxylase (AHH) is a complex mixed function oxidase enzyme which converts polycyclic aromatic hydrocarbons such as DMBA to more hydrophilic and readily excretable products. During this process metabolites that are more carcinogenic than the parent compound can be produced. The distribution of MFO enzymes, their activity, and the balance between conversion of procarcinogens to active carcinogens and their detoxification is probably a... 

Approximately 300 organic pesticide chemicals are being marketed in more than 10,000 different formulations. Last year over 750 million pounds were used in the United States. Insecticides account for nearly half this amount, but herbicides will far surpass them in tonnage within a few years. The chlorinated hydrocarbon insecticides have attracted attention because of their so-called persistence However, unlike some of their inorganic predecessors, organic pesticides are decomposed in the environment by biological and physicochemical processes which influence the amounts that will be found in the environment. Their mere presence in the environment does not necessarily jeopardize the public health. The amounts present, their toxicities, and the rate of detoxification and decomposition must be considered to assess their significance in the environment... 

Aryl hydrocarbon hydroxylase (AHH) is part of the microsomal mixed-function oxidase system involved in the detoxification of polycyclic aromatic hydrocarbons. In the HPLC assay developed for the AHH activity, benzo[a]pyrene (BaP) is used as the substrate, and the activity is determined by measuring the unreacted BaP during the reaction. 

In situ catalytic hydrodechlorination of chlorinated hydrocarbons in wastewater can be used for detoxification of process wastewater or groundwater contaminated with low-molecular weight chlorinated hydrocarbons such as trichloroethylene and trichloroethane. The advantage of this approach is that it consists of a single-step process which can be carried out under ambient conditions. 

The efficacy of land treatment for spills of oil and oil products is confirmed in carefully controlled experiments in the laboratory and in the field. Thus, the hydrocarbons in gasoline, jet fuel, and heating oil are extensively degraded in soils treated with fertilizer, lime, and simulated tilling. This approach reduces the total hydrocarbons by up to 95%, eliminates polycyclic aromatic hydrocarbons, and results in complete detoxification in a few months. Crude oil, crankcase oil, jet fuel, heating oil, and diesel oil disappear faster than in a soil without these treatments. 

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