Sequential participation of glutathione and sulph‐hydryl (S) in reductive dechlorination of 2, 4‐di‐, and 2, 4, 5‐trichloro phenacyl chlorides by soluble fraction (105,000 x g) of chicken liver homogenate.

Akhtar, M. Humayoun

doi:10.1080/03601237909372114

Cited by 4 publications

(4 citation statements)

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“…Previous studies showed that the reduction of toxic α-haloketones to nontoxic acetophenones requires glutathione (11,(16)(17)(18). In the initially proposed reaction mechanism, α-haloketones react nonenzymatically with glutathione to yield S-(phenacyl)glutathiones, which are the true substrates of an enzyme that was termed S-(phenacyl)glutathione reductase (SPG-R) (18,19).…”

Section: Introductionmentioning

confidence: 99%

Glutathione Transferase Omega 1 Catalyzes the Reduction of S-(Phenacyl)glutathiones to Acetophenones

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Anders

2006

Chem. Res. Toxicol.

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S-(Phenacyl)glutathione reductase (SPG-R) plays a significant role in the biotransformation of reactive α-haloketones to non-toxic acetophenones. Comparison of the apparent subunit size, aminoacid composition, and catalysis of the reduction of S-(phenacyl)glutathiones indicated that a previously described rat SPG-R (Kitada et al. (1985) J. Biol. Chem. 260,11749-11754) is homologous to the omega-class glutathione transferase GSTO1-1. The available data show that the SPG-R reaction is catalyzed by GSTO1-1 and not by other GSTs, including the closely related GSTO2-2 isoenzyme. In the proposed reaction mechanism, the active-site cysteine residue of GSTO1-1 reacts with the S-(phenacyl)glutathione substrate to give an acetophenone and a mixed disulfide with the active-site cysteine; a second thiol substrate (e.g., glutathione or 2-mercaptoethanol) reacts with the active-site disulfide to regenerate the catalytically active enzyme and to form a mixed disulfide. A new spectrophotometric assay was developed that allows the rapid determination of SPG-R activity and specific measurement of GSTO1-1 in the presence of other GSTs. This is the first specific reaction attributed to GSTO1-1, and these results demonstrate the catalytic diversity of GSTO1-1, which, in addition to SPG-R activity, catalyzes the reduction of dehydroascorbate and monomethylarsonate (V) and also possesses thioltransferase and GST activity.

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Section: Introductionmentioning

confidence: 99%

Glutathione Transferase Omega 1 Catalyzes the Reduction of S-(Phenacyl)glutathiones to Acetophenones

Board

Anders

2006

Chem. Res. Toxicol.

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“…If direct hydrolysis of I via P-0-vinyl cleavage to I11 had been the major route, a large amount of V and other metabolites would have been observed in the 3-h urine samples. In this connection it should be pointed out that the facile conversion of I11 to V via IV, in in vitro studies, is well established (Akhtar, 1979;Hutson et al, 1976).…”

Section: Resultsmentioning

confidence: 89%

“…It has been shown previously that I11 is very efficiently converted into a glutathione conjugate. The conjugate in turn is further metabolized to other products (Akhtar, 1979;Hutson et al, 1976). The fact that IV was not detected is also explained by the studies of Akhtar (1979), who showed that IV was efficiently reduced to V Residues of VI were not detected in the current study despite the fact that they had been shown to be present in in vitro studies with the soluble fraction from bovine liver homogenates (Akhtar and Foster, 1979).…”

Section: Resultsmentioning

confidence: 98%

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Metabolism and excretion of tetrachlorvinphos in dairy cows

Akhtar¹,

Foster²

1980

J. Agric. Food Chem.

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Metabolism and excretion of tetrachlorvinphos were studied in dairy cows after oral administration for 5 days, followed by no treatment for a 10-day period. Orally administered tetrachlorvinphos (50 ppm, based on average daily ration intake) was absorbed, extensively metabolized, and almost totally eliminated in 10 days following the end of treatment. Traces of unchanged insecticide were detected in urine. The metabolites identified in hydrolyzed urine were as follows: desmethyl tetrachlorvinphos (13.2 % ), l-(2,4,5-trichlorophenyl)ethanol (34.8%), (2,4,5-trichlorophenyl)ethane-1,2-diol (28.1 %), and 2,4,5-trichloromandelic acid (6.1 % ). In addition, unchanged insecticide (7.1 %) as well as significant amounts of 1-(2,4,5-trichlorophenyl)ethanol (8.7%) was excreted in the feces. Neither unchanged insecticide nor metabolites could be detected in milk and various tissues from treated lactating cows.

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The in‐vivo metabolism of propetamphos by insecticide‐resistant and susceptible strains of the housefly, Musca domestica

1986

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The metabolism of propetamphos by insecticide-resistant and susceptible houseflies, in vivo, was investigated. Two major pathways of propetamphos degradation were found. The first is the major route of detoxification for both resistant and susceptible strains at low doses and involves a hydrolysis of the P-0-vinyl bond, ultimately resulting in the formation of carbon dioxide. The second major pathway involves conjugation. As the dose increases, so does the importance of this pathway. Those strains of houseflies with greater conjugative capacity are able to tolerate greater doses of propetamphos than those strains with lesser conjugative capacity. The properties exhibited by this conjugate are consistent with those of glutathione conjugates. This is further supported by a parallel between reported values of glutathione S-transferase activity in the houseflies tested and tolerance to propetamphos.

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Sequential participation of glutathione and sulph‐hydryl (S) in reductive dechlorination of 2, 4‐di‐, and 2, 4, 5‐trichloro phenacyl chlorides by soluble fraction (105,000 x g) of chicken liver homogenate.

Cited by 4 publications

References 11 publications

Glutathione Transferase Omega 1 Catalyzes the Reduction of S-(Phenacyl)glutathiones to Acetophenones

Glutathione Transferase Omega 1 Catalyzes the Reduction of S-(Phenacyl)glutathiones to Acetophenones

Metabolism and excretion of tetrachlorvinphos in dairy cows

The in‐vivo metabolism of propetamphos by insecticide‐resistant and susceptible strains of the housefly, Musca domestica

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