Specificity of murine glutathione S- transferase isozymes in the glutathione conjugation of ()- anti- and (+)-syn-stereoisomers of benzo[g]chrysene 11,12-diol 13,14-epoxide
Ajai Pal,
Albrecht Seidel1,2,
Hong Xia,
Xun Hu,
Sanjay K. Srivastava,
Franz Oesch1 and
Shivendra V. Singh3
Cancer Research Laboratory, Mercy Cancer Institute, Mercy Hospital of Pittsburgh, Pittsburgh, PA 15219, USA and
1 Institute of Toxicology, University of Mainz, Obere Zahlbacher Strasse 67, D-55131, Mainz, Germany
 |
Abstract
|
---|
Specificities of murine glutathione (GSH) S-transferase (GST) isozymes mGSTA1-1, mGSTA2-2, mGSTA3-3 and mGSTA4-4 (
class), mGSTP1-1 (
class) and mGSTM1-1 (µ class) for GSH conjugation of ()-anti- and (+)-syn-stereoisomers of benzo[g]chrysene 11,12-diol 13,14-epoxide (B[g]CDE), the activated metabolites of the environmental pollutant benzo[g]chrysene (B[g]C), have been determined. When GST activity was determined as a function of varying ()-anti- or (+)-syn-B[g]CDE concentration (10320 µM) at a fixed saturating concentration of GSH (2 mM), each isozyme obeyed MichaelisMenten kinetics. mGSTA1-1 was significantly more efficient than other murine GSTs in the GSH conjugation of not only ()-anti-stereoisomer but also (+)-syn-B[g]CDE. For example, the catalytic efficiency (kcat/Km) of mGSTA1-1 towards ()-anti-B[g]CDE was ~2.3- to 16.6-fold higher compared with other murine GSTs. Likewise, mGSTA1-1 was ~2.7-, 6.7-, 4.4- and 12.4-fold more efficient than mGSTA2-2, mGSTA3-3, mGSTP1-1 and mGSTM1-1, respectively, in catalyzing the GSH conjugation of (+)-syn-B[g]CDE. Interestingly, mGSTA4-4, which also belongs to class
, was virtually inactive towards both stereoisomers of B[g]CDE. The results of the present study indicate that murine GSTs, especially
class isozymes, significantly differ in their ability to detoxify B[g]CDE stereoisomers and that mGSTA1-1 plays a major role in the detoxification of both ()-anti- and (+)-syn-B[g]CDE, which among four B[g]CDE stereoisomers are formed from the carcinogen B[g]C as major DNA binding metabolites.
Abbreviations: B[g]C, benzo[g] chrysene; B[g]CDE, benzo[g]chrysene 11,12-diol 13,14-epoxide; BPDE, benzo[a]pyrene 7,8-diol 9,10-epoxide; GSH, glutathione; GST, glutathione S-transferase; PAHs, polycyclic aromatic hydrocarbons.
 |
Introduction
|
---|
Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental pollutants and known to produce tumors at various sites in laboratory animals (14). Moreover, these compounds are suspected human carcinogens (4). The tumorigenicity of PAHs is predominantly linked to the formation of diol epoxides, which are generated through cytochrome P450- and microsomal epoxide hydrolase-mediated activation of the parent hydrocarbons (2,3). The diol epoxides implicated as the active metabolites of PAH carcinogens generally have the epoxide function in a bay or a fjord region (5). The diol epoxides of both bay and fjord region classes exist as a pair of optical enantiomers [(+)- and ()-enantiomer] of two diastereomers (anti- and syn-isomers) (3,5). In the case of bay region diol epoxides, e.g. benzo[a]pyrene 7,8-diol 9,10-epoxide-(BPDE), the stereoisomer with (7R,8S)-diol (9S,10R)-epoxide absolute configuration [(+)-anti-BPDE] is significantly more tumorigenic than the other three stereoisomers [refer to Figure 1
for structure and absolute configuration of (+)-anti-BPDE] (6,7). For fjord region diol epoxides, e.g. benzo[g]chrysene 11,12-diol 13,14-epoxide (B[g]CDE), both the ()-anti-stereoisomer with the (11R,12S)-diol (13S,14R)-epoxide absolute configuration and the (+)-syn-stereoisomer with the (11S,12R)-diol (13S,14R)-epoxide absolute configuration (Figure 1
) possess high tumorigenic activity (810). Moreover, the diol epoxides of the fjord region class are relatively more potent carcinogens than corresponding bay region compounds. For example, it has been demonstrated that racemic anti-B[g]CDE, the activated form of the environmental pollutant benzo[g]chrysene (B[g]C), is a far more potent tumor initiator than anti-BPDE (11). While covalent interaction of the PAH diol epoxides with nucleophilic centers in DNA is a critical event in PAH-induced tumorigenesis (1,3), glutathione (GSH) S-transferases (GSTs) play an important role in their cellular detoxification (1214).

View larger version (17K):
[in this window]
[in a new window]
|
Fig. 1. Structures and absolute configurations of (+)-anti-benzo[a]pyrene 7,8-diol 9,10-epoxide, ()-anti-benzo[g]chrysene 11,12-diol 13,14-epoxide and (+)-syn-benzo[g]chrysene 11,12-diol 13,14-epoxide.
|
|
GSTs are a superfamily of isozymes that catalyze the GSH conjugation of a wide variety of electrophilic compounds, generally leading to their detoxification (15,16). The cytosolic GST activity in mammalian tissues is often due to multiple isozymes, grouped into four major classes,
, µ,
and
, which exhibit overlapping but distinct substrate specificities (1518). For example, the
class human and rat GSTs are poor in catalyzing the GSH conjugation of (+)-anti-BPDE (12), which is the activated form of benzo[a]pyrene (BP) (3).
Recently, we have identified a novel
class GST isozyme in tissues of female A/J mouse (previously designated GST 9.5), which is between 9- and 625-fold more efficient than other murine GSTs in the GSH conjugation of (+)-anti-BPDE (19). More recently, we have cloned the cDNAs for both the subunits of GST 9.5 and demonstrated that this isozyme is composed of A1 and A2 type murine GST subunits and that the A1 type subunit is responsible for its exceptional activity towards (+)-anti-BPDE (20). However, the specificity of murine GSTs, especially mGSTA1-1, in catalyzing the GSH conjugation of fjord region diol epoxides is poorly characterized.
In the present study we have compared catalytic efficiencies of murine GSTs in the GSH conjugation of ()-anti- and (+)-syn-stereoisomers of B[g]CDE, the two stereoisomers to which the moderate carcinogen B[g]C is metabolically activated in mouse skin (21). The results of the present study indicate that murine GSTs significantly differ in their ability to detoxify B[g]CDE stereoisomers and that mGSTA1-1 is significantly more efficient than other murine GSTs towards both ()-anti- and (+)-syn-B[g]CDE. In conclusion, our results indicate that mGSTA1-1 plays a major role in the detoxification of both bay region and fjord region PAH diol epoxides.
 |
Materials and methods
|
---|
Materials
Female A/J mice (~8 weeks old) were purchased from the National Cancer Institute Frederick Cancer Research and Development Center (Frederick, MD). Reagents including GSH and epoxy-activated Sepharose 6B were purchased from Sigma (St Louis, MO). Individual enantiomers of B[g]CDE were prepared from optically active B[g]C 11,12-diols according to published methods (22). The specific rotations of the enantiomeric B[g]CDE were in good accordance with the reported values (22). Other reagents were of the highest purity available.
Purification of GST isozymes
Previous studies from our laboratory have shown that >90% of total GST activity in various organs of female A/J mouse is due to mGSTA1-1, mGSTA2-2, mGSTA3-3, mGSTA4-4, mGSTM1-1 and/or mGSTP1-1 (20,23). We therefore selected the above isozymes for their kinetic characterization towards B[g]CDE stereoisomers. Recombinant mGSTA1-1 and mGSTA2-2 were expressed and purified by GSH affinity chromatography as described previously (20). Recombinant mGSTA4-4 was a generous gift from Dr Piotr Zimniak (University of Arkansas for Medical Sciences, Little Rock, AR). Other murine GST isozymes were purified from the liver of female A/J mice using a protocol that involves GSH affinity chromatography followed by chromatofocusing, as described previously (23). The GSH affinity chromatography was performed by the method of Simons and Vander Jagt (24) with some modifications described previously (25). Protein content was determined by the Bradford method (26). The homogeneity and classification of the above GST isozymes was ascertained by reverse phase HPLC and western blot analysis, respectively, as described previously (23).
Determination of GST activity towards B[g]CDE stereoisomers
The purified GST isozymes were dialyzed against 50 mM TrisHCl (pH 7.5) containing 2.5 mM KCl and 0.5 mM EDTA (TKE buffer) and stored at 20°C until used. The activity of each isozyme towards the model substrate 1-chloro-2,4-dinitrobenzene was determined (27) prior to activity measurements towards B[g]CDE stereoisomers. The reaction mixture in a final volume of 0.1 ml contained TKE buffer, 2 mM GSH and the desired concentrations of the B[g]CDE stereoisomer (10320 µM) and GST isozyme protein. The GST isozymes were used at the following concentrations: mGSTA3-3, 100 µg/ml; mGSTP1-1, 30 µg/ml; mGSTM1-1, 86 µg/ml; recombinant mGSTA4-4, mGSTA1-1 and mGSTA2-2, 30 µg/ml. The reaction was started by adding B[g]CDE stereoisomer and the reaction mixture was incubated for 30 s at 37°C. The GST isozyme protein concentrations and incubation time specified above were selected based on our previous studies with murine GSTs using racemic anti-B[g]CDE (28). The reaction was terminated by rapid mixing with 0.1 ml chilled acetone and the reaction mixture was extracted with TKE buffer saturated with ethyl acetate. The GSH conjugates of B[g]CDE stereoisomers in the aqueous phase were quantified by reverse phase HPLC using a Waters Nova-Pak C18 (3.9x150 mm) column. The GSH conjugates of ()-anti- and (+)-syn-B[g]CDE were eluted isocratically (18.6% acetonitrile in 0.1% trifluoroacetic acid) at retention times of ~5.2 and 10.3 min, respectively. The concentrations of the GSH conjugates of ()-anti- and (+)-syn-B[g]CDE were determined using the molar extinction coefficients reported by Jernström et al. (29). A control without the GST protein was also included to account for non-enzymatic conjugation of GSH with B[g]CDE. The kinetic constants (Km and Vmax) were estimated by fitting a hyperbolic function to the data points through non-linear regression analysis.
 |
Results and discussion
|
---|
Non-enzymatic (spontaneous) GSH conjugation of ()-anti-B[g]CDE was not detectable. On the other hand, this reaction was accelerated to varying degrees in the presence of different GST isozymes. When GST activity was determined as a function of varying ()-anti-B[g]CDE concentration (10320 µM) at a fixed saturating concentration of GSH (2 mM), each isozyme obeyed MichaelisMenten kinetics (plots not shown). As shown in Table I
, the
class isozyme mGSTA1-1 was significantly more efficient than other murine GSTs in the GSH conjugation of ()-anti-B[g]CDE. For example, the catalytic efficiency of mGSTA1-1 towards ()-anti-B[g]CDE was ~6.4-, 16.6- and 7.5-fold higher compared with mGSTA3-3, mGSTP1-1 and mGSTM1-1, respectively. This was mainly due to a relatively higher Vmax (~2.6- to 4.4-fold higher) and considerably lower Km (~6071% lower) for mGSTA1-1 than for mGSTA3-3, mGSTP1-1 and mGSTM1-1. Even though the Vmax for mGSTA1-1 was slightly lower than that for mGSTA2-2, the former isozyme was ~2.3-fold more efficient than mGSTA2-2 in the GSH conjugation of ()-anti-B[g]CDE. mGSTA4-4, which also belongs to class
, was virtually inactive towards this substrate.
View this table:
[in this window]
[in a new window]
|
Table I. Kinetic constants for murine GSTs towards ()-anti- and (+)-syn-B[g]CDE stereoisomers [values for (+)-syn-B[g]CDE are given in parentheses]
|
|
Similarly to ()-anti-B[g]CDE, non-enzymatic conjugation of the (+)-syn-enantiomer of B[g]CDE with GSH could not be detected. Adherence to MichaelisMenten kinetics was also observed for each isozyme when GST activity was measured as a function of varying (+)-syn-B[g]CDE concentration (10320 µM) at 2 mM GSH concentration (plots not shown). The kinetic constants for murine GSTs in the GSH conjugation of (+)-syn-B[g]CDE are also summarized in Table I
(parentheses). Similarly to the ()-anti-enantiomer, mGSTA1-1 was significantly more efficient (~2.7- to 12.4-fold) than other murine GSTs in the GSH conjugation of (+)-syn-B[g]CDE. While catalytic efficiencies for
class isozymes mGSTA1-1, mGSTA2-2 and mGSTA3-3 towards ()-anti- and (+)-syn-B[g]CDE were comparable, mGSTP1-1 was 4-fold more efficient towards (+)-syn-stereoisomer than towards ()-anti-B[g]CDE (Table I
). On the other hand, mGSTM1-1 was ~1.6-fold more efficient towards ()-anti-B[g]CDE compared with the (+)-syn-stereoisomer.
The results of the present study indicate that mGSTA1-1 is significantly more efficient than other classes of murine GSTs, including those of class
, in the GSH conjugation of both the ()-anti- and (+)-syn-stereoisomers of B[g]CDE, which are the activated metabolites of the environmental pollutant B[g]C (21,30). The catalytic efficiency of mGSTA1-1 towards B[g]CDE stereoisomers is ~2.3- to 16.6-fold higher than those of other murine GSTs examined in the present study. We have shown previously that mGSTA1-1 is ~3- to 655-fold more effective than mGSTA2-2, mGSTA3-3, mGSTA4-4, mGSTP1-1 and mGSTM1-1 in catalyzing the GSH conjugation of bay region diol epoxide (+)-anti-BPDE (20), another environmentally relevant PAH diol epoxide (14). Taken together, these observations suggest that mGSTA1-1 may play a major role in the GSH conjugation (detoxification) of not only bay region compounds but also the PAH diol epoxides of the fjord region class (e.g. B[g]CDE).
Previous studies with human GST isozymes have also demonstrated that the catalytic efficiency of hGSTA1-1 is between 1.3- and 5.9-fold higher compared with hGSTM1-1 and hGSTP1-1 towards the ()-anti- and (+)-syn-B[g]CDE stereoisomers (13). Unlike mouse GSTA1-1, however, human GSTA1-1 is relatively more effective towards the (+)-syn-B[g]CDE compared with the ()-anti-enantiomer of B[g]CDE (13). Mouse GSTA1-1 is equally efficient in the GSH conjugation of the ()-anti- and (+)-syn-B[g]CDE isomers (Table I
).
The results of the present study reveal that the
class murine GSTs markedly differ in their ability to detoxify B[g]CDE. For example,
class isozyme mGSTA4-4, which shares ~59% amino acid sequence identity with mGSTA1-1 (20,31), is virtually inactive towards both the ()-anti- and (+)-syn-B[g]CDE stereoisomers. Even though mGSTA2-2 and mGSTA3-3, which respectively share ~96 and 69% amino acid sequence identities with mGSTA1-1 (20,32,33), can catalyze the GSH conjugation of both ()-anti- and (+)-syn-B[g]CDE, their catalytic efficiencies are significantly lower compared with mGSTA1-1. These observations, taken together with the results of previous studies, suggest that
class murine GSTs may have a unique role in the detoxification of xenobiotics. For example, while mGSTA1-1 seems to be important in the detoxification of PAH diol epoxides (20; present study), this isozyme may have a limited role in cellular protection against 4-hydroxynonenal, which is the toxic end product of lipid peroxidation. Instead, the majority of the GST-mediated detoxification of 4-hydroxynonenal may be carried out by mGSTA4-4, as the specific activity of this isozyme towards 4-hydroxynonenal (55 µmol/min/mg protein) is ~162-, 83- and 50-fold higher compared with mGSTA1-1, mGSTA2-2 and mGSTA3-3, respectively (16,20). On the other hand, mGSTA3-3 may play a major role in cellular protection against other oxidative products such as lipid hydroperoxides (16). For example, the specific activity of mGSTA3-3 towards cumene hydroperoxide (12 µmol/min/mg protein) is ~9-, 4- and 17-fold higher compared with mGSTA1-1, mGSTA2-2 and mGSTA4-4, respectively (16,20).
Previous studies have shown that the diol epoxides of the fjord region class are relatively more potent mutagens in bacterial and mammalian cells (34) and more potent carcinogens in animal models than corresponding diol epoxides of the bay region class (611). For example, it has been shown that racemic anti-B[g]CDE is a far more potent tumor initiator compared with anti-BPDE (11). The results of the present study, taken together with our previous studies, reveal that the catalytic efficiencies of murine GSTs is significantly lower towards B[g]CDE stereoisomers (present study) compared with corresponding bay region diol epoxides (20). For example, the catalytic efficiency of mGSTA1-1 towards anti-BPDE stereoisomer with the (7R,8S)-diol (9S,10R)-epoxide absolute configuration [(+)-anti-stereoisomer] (131/mM/s; 20) is ~16-fold higher than towards the B[g]CDE stereoisomer with a similar absolute configuration [()-anti-B[g]CDE] (present study). Likewise, the catalytic efficiencies of mGSTA2-2 and mGSTP1-1 towards (+)-anti-BPDE are significantly higher compared with the corresponding enantiomer of B[g]CDE (20; present study). On the other hand, some isozymes, such as mGSTA3-3 and mGSTM1-1, exhibit comparable catalytic efficiency towards both above diol epoxides. These observations suggest that relatively higher carcinogenic potency of fjord region compounds compared with diol epoxides of the bay region class may, at least in part, be due to a relatively lower capacity of GSTs to detoxify the former compounds. On the other hand, differences in the DNA adduction profile for bay region and fjord region diol epoxides may also be important in their differential carcinogenic potency. For example, it has been shown that while guanine residues in DNA are the principal site of reaction for bay region dihydrodiol epoxides (e.g. anti-BPDE), both adenine and guanine residues are modified by the dihydrodiol epoxides of the fjord region class, such as anti-B[g]CDE (3537).
In conclusion, the results of the present study indicate that murine GSTs, particularly the isozymes of class
, significantly differ in their ability to detoxify B[g]CDE stereoisomers and that the
class isozyme mGSTA1-1 is significantly more efficient than other classes of murine GSTs in the GSH conjugation of both stereoisomers [()-anti- and (+)-syn-] of B[g]CDE. Thus, it seems reasonable to conclude that mGSTA1-1 plays a major role in the detoxification of both bay region and fjord region PAH diol epoxides.
 |
Acknowledgments
|
---|
This investigation was supported in part by USPHS grant CA 76348 (S.V.S.), awarded by the National Cancer Institute, and the Deutsche Forschungsgemeinschaft, SFB 302 (A.S.).
 |
Notes
|
---|
2 Present address: Biochemical Institute for Environmental Carcinogens, Prof. Dr Gernot Grimmer Foundation, Lurup 4, D-22927 Grosshansdorf, Germany 
3 To whom correspondence should be addressedEmail: ssingh{at}mercy.pmhs.org 
 |
References
|
---|
-
Dipple,A., Moschel,R.C. and Bigger,C.A.H. (1984) Polynuclear aromatic carcinogens. In Searle,C.E. (ed.) Chemical Carcinogens. American Chemical Society, Washington, DC, Vol. 1, pp. 41163.
-
Harvey,R.G. (1991) Polycyclic Aromatic Hydrocarbons: Chemistry and Carcinogenesis. Cambridge University Press, Cambridge, UK.
-
Thakker,D.R., Yagi,H., Levin,W., Wood,A.W., Conney,A.H. and Jerina,D.M. (1985) Polycyclic aromatic hydrocarbons: metabolic activation to ultimate carcinogens. In Anders,M.W. (ed.) Bioactivation of Foreign Compounds. Academic Press, New York, NY, pp. 177242.
-
International Agency for Research on Cancer (1983) IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans: Polynuclear Aromatic Compounds, Part 1. Chemical, Environmental and Experimental Data. IARC Scientific Publications no. 32, IARC, Lyon.
-
Jerina,D.M. and Daly,J.W. (1976) Oxidation of carbon. In Parke,D.V. and Smith,R.L. (eds.) Drug MetabolismFrom Microbe to Man. Taylor & Francis, London, UK, pp. 1332.
-
Buening,M.K., Wislocki,P.G., Levin,W., Yagi,H., Thakker,D.R., Akagi,H., Koreeda,M., Jerina,D.M. and Conney,A.H. (1978) Tumorigenicity of the optical enantiomers of the diastereomeric benzo[a]pyrene-7,8-diol-9,10-epoxides in newborn mice: exceptional activity of (+)-7ß,8
-dihydroxy-9
,10
-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene. Proc. Natl Acad. Sci. USA, 75, 53585361.[Abstract]
-
Slaga,T.J., Bracken,W.J., Gleason,G., Levin,W., Yagi,H., Jerina,D.M. and Conney,A.H. (1979) Marked differences in the skin tumor-initiating activities of the optical enantiomers of the diastereomeric benzo[a]pyrene 7,8-diol-9,10-epoxides. Cancer Res., 39, 6771.[ISI][Medline]
-
Levin,W., Chang,R.L., Wood,A.W., Thakker,D.R., Yagi,H., Jerina,D.M. and Conney,A.H. (1986) Tumorigenicity of optical isomers of the diastereomeric bay-region 3,4-diol-1,2-epoxides of benzo[c]phenanthrene in murine tumor models. Cancer Res., 46, 22572261.[Abstract]
-
Hecht,S.S., El-Bayoumy,K., Rivenson,A. and Amin,S. (1994) Potent mammary carcinogenicity in female CD rats of a fjord region diol-epoxide of benzo[c]phenanthrene compared to a bay region diol-epoxide of benzo[a]pyrene. Cancer Res., 54, 2124.[Abstract]
-
Amin,S., Desai,D., Dai,W., Harvey,R.G. and Hecht,S.S. (1995) Tumorigenicity in newborn mice of fjord region and other sterically hindered diol epoxides of benzo[g]chrysene, dibenzo[a,l]pyrene (dibenzo(def,p)chrysene), 4H-cyclopenta(def)chrysene and fluoranthene. Carcinogenesis, 16, 28132817.[Abstract]
-
Amin,S., Krzeminski,J., Rivenson,A., Kurtzke,C., Hecht,S.S. and El-Bayoumy,K. (1995) Mammary carcinogenicity in female CD rats of fjord region diol epoxides of benzo[c]phenanthrene, benzo[g]chrysene and dibenzo[a,l]pyrene. Carcinogenesis, 16, 19711974.[Abstract]
-
Robertson,I.G.C., Guthenberg,C., Mannervik,B. and Jernström,B. (1986) Differences in stereoselectivity and catalytic efficiency of three human glutathione transferases in the conjugation of glutathione with 7ß,8
-dihydroxy-9
,10
-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene. Cancer Res., 46, 22202224.[Abstract]
-
Sundberg,C., Widersten,M., Seidel,A., Mannervik,B. and Jernström,B. (1997) Glutathione conjugation of bay- and fjord-region diol epoxides of polycyclic aromatic hydrocarbons by glutathione transferases M1-1 and P1-1. Chem. Res. Toxicol., 10, 12211227.[ISI][Medline]
-
Hesse,S., Jernström,B., Martinez,M., Moldéus,P., Christodoulides,L. and Ketterer,B. (1982) Inactivation of DNA-binding metabolites of benzo[a]pyrene and benzo[a]pyrene-7,8-dihydrodiol by glutathione and glutathione S-transferases. Carcinogenesis, 3, 757760.[ISI][Medline]
-
Mannervik,B. (1985) The isoenzymes of glutathione transferase. Adv. Enzymol. Relat. Areas Mol. Biol., 57, 357417.[Medline]
-
Hayes,J.D. and Pulford,D.J. (1995) The glutathione S-transferase supergene family: regulation of GST* and the contribution of the isoenzymes to cancer chemoprotection and drug resistance. Crit. Rev. Biochem. Mol. Biol., 30, 445600.[Abstract]
-
Mannervik,B., Ålin,P., Guthenberg,C., Jensson,H., Tahir,M.K., Warholm,M. and Jörnvall,H. (1985) Identification of three classes of cytosolic glutathione transferase common to several mammalian species: correlation between structural data and enzymatic properties. Proc. Natl Acad. Sci. USA, 82, 72027206.[Abstract]
-
Meyer,D.J., Coles,B., Pemble,S.E., Gilmore,K.S., Fraser,G.M. and Ketterer,B. (1991) Theta, a new class of glutathione transferases purified from rat and man. Biochem. J., 274, 409414.[ISI][Medline]
-
Hu,X., Srivastava,S.K., Xia,H., Awasthi,Y.C. and Singh,S.V. (1996) An alpha class mouse glutathione S-transferase with exceptional catalytic efficiency in the conjugation of glutathione with 7ß,8
-dihydroxy-9
,10
-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene. J. Biol. Chem., 271, 3268432688.[Abstract/Free Full Text]
-
Xia,H., Pan,S.-S., Hu,X., Srivastava,S.K., Pal,A. and Singh,S.V. (1998) Cloning, expression and biochemical characterization of a functionally novel alpha class glutathione S-transferase with exceptional activity in the glutathione conjugation of (+)-anti-7,8-dihydroxy-9,10-oxy-7,8,9,10-tetrahydrobenzo(a)pyrene. Arch. Biochem. Biophys., 353, 337348.[ISI][Medline]
-
Giles,A.S., Seidel,A. and Phillips,D.H. (1996) Covalent DNA adducts formed in mouse epidermis by benzo[g]chrysene. Carcinogenesis, 17, 13311336.[Abstract]
-
Bushman,D.R., Grossman,S.J., Jerina,D.M. and Lehr,R.E. (1989) Synthesis of optically active fjord-region 11,12-diol 13,14-epoxides and the K-region 9,10-oxide of the carcinogen benzo[g]chrysene. J. Org. Chem., 54, 35333544.[ISI]
-
Hu,X., Benson,P.J., Srivastava,S.K., Mack,L.M., Xia,H., Gupta,V., Zaren,H.A. and Singh,S.V. (1996) Glutathione S-transferases of female A/J mouse liver and forestomach and their differential induction by anti-carcinogenic organosulfides from garlic. Arch. Biochem. Biophys., 336, 199214.[ISI][Medline]
-
Simons,P.C. and Vander Jagt,D.L. (1977) Purification of glutathione S-transferases from human liver by glutathione-affinity chromatography. Anal. Biochem., 82, 334341.[ISI][Medline]
-
Singh,S.V., Leal,T., Ansari,G.A.S. and Awasthi,Y.C. (1987) Purification and characterization of glutathione S-transferases of human kidney. Biochem. J., 246, 179186.[ISI][Medline]
-
Bradford,M.M. (1976) A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of proteindye binding. Anal. Biochem., 72, 248254.[ISI][Medline]
-
Habig,W.H., Pabst,M.J. and Jakoby,W.B. (1974) Glutathione S-transferases: the first enzymatic step in mercapturic acid formation. J. Biol. Chem., 249, 71307139.[Abstract/Free Full Text]
-
Hu,X. and Singh,S.V. (1997) Differential catalytic efficiency and enantioselectivity of murine glutathione S-transferase isoenzymes in the glutathione conjugation of carcinogenic anti-diol epoxides of chrysene and benzo(g)chrysene. Arch. Biochem. Biophys., 345, 318324.[ISI][Medline]
-
Jernström,B., Funk,M., Frank,H., Mannervik,B. and Seidel,A. (1996) Glutathione S-transferase A1-1-catalysed conjugation of bay and fjord region diol epoxides of polycyclic aromatic hydrocarbons with glutathione. Carcinogenesis, 17, 14911498.[Abstract]
-
Agarwal,R., Coffing,S.L., Baird,W.M., Kiselyov,A.S., Harvey,R.G. and Dipple,A. (1997) Metabolic activation of benzo[g]chrysene in the human mammary carcinoma cell line MCF-7. Cancer Res., 57, 415419.[Abstract]
-
Zimniak,P., Eckles,M.A., Saxena,M. and Awasthi,Y.C. (1992) A subgroup of class
glutathione S-transferases. Cloning of cDNA for mouse lung glutathione S-transferase GST 5.7. FEBS Lett., 313, 173176.[ISI][Medline]
-
Pearson,W.R., Reinhart,J., Sisk,S.C., Anderson,K.S. and Adler,P.N. (1988) Tissue-specific induction of murine glutathione transferase mRNAs by butylated hydroxyanisole. J. Biol. Chem., 263, 1332413332.[Abstract/Free Full Text]
-
Hayes,J.D., Judah,D.J., Neal,G.E. and Nguyen,T. (1992) Molecular cloning and heterologous expression of a cDNA encoding a mouse glutathione S-transferase Yc subunit possessing high catalytic activity for aflatoxin B1-8,9-epoxide. Biochem. J., 285, 173180.[ISI][Medline]
-
Glatt,H., Piée,A., Pauly,K., Steinbrecher,T., Schrode,R., Oesch,F. and Seidel,A. (1991) Fjord- and bay-region diol epoxides investigated for stability, SOS induction in Escherichia coli and mutagenicity in Salmonella typhimurium and mammalian cells. Cancer Res., 51, 16591667.[Abstract]
-
Cheng,S.C., Hilton,B.D., Roman,J.M. and Dipple,A. (1989) DNA adducts from carcinogenic and noncarcinogenic enantiomers of benzo[a]pyrene dihydrodiol epoxide. Chem. Res. Toxicol., 2, 334340.[ISI][Medline]
-
Szeliga,J., Lee,H., Harvey,R.G., Page,J.E., Ross,H.L., Routledge,M.N., Hilton,B.D. and Dipple,A. (1994) Reaction with DNA and mutagenic specificity of syn-benzo[g]chrysene 11,12-dihydrodiol 13,14-epoxide. Chem. Res. Toxicol., 7, 420427.[ISI][Medline]
-
Szeliga,J., Page,J.E., Hilton,B.D., Kiselyov,A.S., Harvey,R.G., Dunayevskiy,Y.M., Vouros,P. and Dipple,A. (1995) Characterization of DNA adducts formed by anti-benzo[g]chrysene 11,12-dihydrodiol 13,14-epoxide. Chem. Res. Toxicol., 8, 10141019.[ISI][Medline]
Received March 2, 1999;
revised May 28, 1999;
accepted June 17, 1999.