Journal Article

Specificity of murine glutathione <i>S-</i> transferase isozymes in the glutathione conjugation of (–)- <i>anti</i>- and (+)-<i>syn</i>-stereoisomers of benzo[<i>g</i>]chrysene 11,12-diol 13,14-epoxide

Ajai Pal, Albrecht Seidel, Hong Xia, Xun Hu, Sanjay K. Srivastava, Franz Oesch and Shivendra V. Singh

in Carcinogenesis

Volume 20, issue 10, pages 1997-2001
Published in print October 1999 | ISSN: 0143-3334
Published online October 1999 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/20.10.1997
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

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Specificities of murine glutathione (GSH) S-transferase (GST) isozymes mGSTA1-1, mGSTA2-2, mGSTA3-3 and mGSTA4-4 (α class), mGSTP1-1 (π 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 (10–320 μM) at a fixed saturating concentration of GSH (2 mM), each isozyme obeyed Michaelis–Menten 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 α, was virtually inactive towards both stereoisomers of B[g]CDE. The results of the present study indicate that murine GSTs, especially α 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.

Keywords: 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.

Journal Article.  3546 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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