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Mercapturic acid sulfur

We do not know whether the S-oxidized mercapturic acid of PCMTB (II) is formed in the conventional rat or if it may be a PCMTB metabolite that is unique to the germfree state. It could result from tissue metabolism during the enterohepatic circulation of the mercapturate precursors or the mercapturate (I). If it is formed in the conventional rat, it may be a precursor for the nonextractable fecal residues because no extractable metabolite that contained an oxidized sulfur was found in conventional rat excreta. [Pg.174]

As in the case of propachlor mercapturic acid sulfoxide, the biological significance of xenobiotic mercapturic acids that contain oxidized sulfur is not known. Casida et al. (39) have reported that sulfoxidation of some thiocarbamate herbicides is a beneficial step in the detoxication process. However, cysteine conjugates can exhibit adverse biological activities. Smith (40) has reviewed work on the metabolism of the toxic principle in kale and has shown that C-S lyase action on S-methylcysteine sulfoxide produces the toxic principle. Virtanen ( ) has reviewed the processes in other plants that lead to the production of compounds with biological activity from -substituted cysteine sulfoxides. [Pg.174]

It is assumed that phenols can conjugate directly with D-glucuronic acid or sulfuric acid. The scheme explains why phenols do not conjugate with mercapturic acid. Parke and Williams128 have recently shown that administration of phenylmercapturic acid or phenylcysteine to the rabbit is followed by the excretion of phenylcysteine, ester sulfates, and thio-phenol, and phenylcysteine also yields diphenyl disulfide. The thiol donor... [Pg.216]

Figure 3. Metabolites of sulfur mustard identified by mass spectrometry, derived from an initial reaction with glutathione and metabolized by divergent mercapturic acid and (1-lyase pathways (8)... Figure 3. Metabolites of sulfur mustard identified by mass spectrometry, derived from an initial reaction with glutathione and metabolized by divergent mercapturic acid and (1-lyase pathways (8)...
Figure 9. Identification of metabolites A through D in urine of rats treated with CDA led to the proposed hidden metabolites shown here in brackets. The reactive sulfate conjugate apparently undergoes glutathione conjugation, further metabolism via the mercapturic acid pathway and, finally, C-S cleavage, methylation and sulfur oxidation of C to yield D. Figure 9. Identification of metabolites A through D in urine of rats treated with CDA led to the proposed hidden metabolites shown here in brackets. The reactive sulfate conjugate apparently undergoes glutathione conjugation, further metabolism via the mercapturic acid pathway and, finally, C-S cleavage, methylation and sulfur oxidation of C to yield D.
Sulfoxidation. Sulfoxidation Is common in sulfur biochemistry (43,44), and has been observed with many of the transamination products listed in Table III, with mercapturic acids (45,46,47) and cysteine conjugates (12). Sulfoxidation is also common with the methylthio-containing metabolites produced from cysteine conjugates (see "Thiol Formation" below). Sulfoxidation increases the polarity of compounds and therefore affects their excretability. [Pg.308]

Measuring the total concentration of urinary thio compounds (including glutathione conjugates, mercapturic acids, and other sulfur-containing carbon disulfide metabolites) can serve as a good marker of exposure. The level of total thio compounds correlates with carbon disulfide exposure levels and is a more sensitive biomarker of exposure than the iodine-azide test (Beauchamp et al. 1983 Van Doom et al. [Pg.101]

In addition, two different types of resistance to chlorinated hydrocarbons occur in insects, particularly flies one is to DDT and the other is to dieldrin, chlordane, and benzene hexachloride (BHC). DDT resistance in flies is commonly due to the increased rate of conversion of DDT (dichlorodiphenyl-trichloroethane) (6.41) to DDE (dichlorodiphenyldichloroethylene), which is inactive. This is achieved by an increased production of the enzyme DDT-dehydrochlorinase (Winteringham and Barnes, 1955). The normal function of this dehydrochlorinase is unknown in the mutant which the agent has caused to be selected. Resistance to BHC in houseflies has been traced to its conversion to water-soluble sulfur-containing derivatives, probably mercapturic acids (Bradbury and Standen, 1959). [Pg.260]

Although the mercapturic acids from the monohalobenzenes constitute 35-50% of the administered compounds, with most unsubstituied hydrocarbons the yield of sulfur conjugate is rather small. The proportion of the dose which is excreted as metabolism products is affected by the degree of absorption of the precursor from the gut. This varies remarkably from one compound to another. Also, precursors tend to dissolve in tissue lipid and are released slowly. [Pg.264]

The observation that naphthalene feeding produced cataracts in rabbits suggested a relationship between mercapturic acid formation and sulfur amino acid metabolism in mammals, In the period between World Wars I and II, most advances in the biochemistrj of mei capturic acids were made through study of tlie nutritional effects produced by mercapturic acid precursors. During this period, the concept of mercapturic acids as... [Pg.264]

It is of interest that Grover and Sims (1964) found that aromatic hydrocarbons and narcotics, which induce hydroxylase activity, have a depressant effect on glutathione iS-arjdtransferase. Hydroxylases have a practically unlimited supply of substrate while the conjugases require glutathione, which rapidly depletes the liver. Nevertheless a severe sulfur amino acid defidency be generated by administration of bromo-benzene and other hydrocarbons or derivatives w-hich are metabolized to proportionately large amounts of mercapturic acids. [Pg.285]

When mercapturic acids were administered to rats, the recovery of the original material was quite variable. Marsden and Young (1958) found only 33% of a-naphthylmercapturic acid was excreted unchanged by rats. This was less than half of the neutral sulfur of the urine and it seems probable some naphthyl-L-cysteine was excreted. Parke and Williams (1951) found 45% of a dose of phenylmercapturic acid was excreted unchanged and 14% as phenylcysteine,... [Pg.291]

Tissue extracts which exhibit little acetylation in contrast to slices actively deacetylate mercapturic acids (Bray and James, 19f30). Kidney extracts are more active than liver. The deacetylase content of extracts of rat, rabbit, and guinea pig liver were roughly equivalent but varied with the type of substituent on the sulfur. For example, the rabbit dc-acetylase activity toward jV-acetyl-S-benzyl-L-cysteine was low, w hereas toward iV-acetyI- S-butylcysteine it w as high. Bray and James concluded that there is little to support the view that tiie failure of the guinea pig to excrete significant amounts of mercapturic acids is due to the deacetylase activity of its tissues. Probably the failure is in part in the acetylation process and in part due to convemion of the S-substituted cysteines into other metabolism products. [Pg.292]

Early studies on the metabolism of mercapturic acids involved determination of the sulfur distribution in the urine as sulfate, neutral sulfur, and ethereal sulfate. The procedures used were incapable of detecting minor metabolites. Changes in the neutral sulfur were assumed to arise from excretion of mercapturic acids particularly. [Pg.292]

On this basis, Shiple el oi. (1924) concluded that mercapturic acids are oxidized to ethereal sulfates. Later Coombs and Hele (1927) and I.ia wrie (1931) decided mercapturic acids are not oxidized in vivo. Krie (1932) found, S-benzylcysteine was not oxidized to any extent in the dog, in contrast to 36% in the rabbit (Sherwdn el al., 1927). Urinary sulfur distributions in general proved an unreliable index of mercapturic acid... [Pg.292]

Table I. Examples of NMR usage in Identification of amino acid conjugates. Cysteine, mercapturate (N-acetylcysteine), glutathione, cystelnylglyclne, and glutamylcysteine are all conjugated through sulfur. Table I. Examples of NMR usage in Identification of amino acid conjugates. Cysteine, mercapturate (N-acetylcysteine), glutathione, cystelnylglyclne, and glutamylcysteine are all conjugated through sulfur.

See other pages where Mercapturic acid sulfur is mentioned: [Pg.265]    [Pg.293]    [Pg.265]    [Pg.293]    [Pg.356]    [Pg.55]    [Pg.165]    [Pg.69]    [Pg.71]    [Pg.240]    [Pg.216]    [Pg.218]    [Pg.240]    [Pg.1689]    [Pg.406]    [Pg.1689]    [Pg.240]    [Pg.186]    [Pg.335]    [Pg.671]    [Pg.352]    [Pg.320]    [Pg.671]    [Pg.115]    [Pg.1068]    [Pg.60]    [Pg.265]    [Pg.266]    [Pg.267]    [Pg.270]    [Pg.287]    [Pg.194]    [Pg.28]   


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Mercapturate

Mercapturic acid

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