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Updated: Mar 30, 2026

Spectrophotometric Screening for Potential Inhibitors of Cytosolic Glutathione S-Transferases
Published on: October 10, 2020
Benzene oxide is a substrate for glutathione S-transferases
Adam T Zarth1, Sharon E Murphy2, Stephen S Hecht1
1Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA; Medicinal Chemistry Graduate Program, University of Minnesota, Minneapolis, MN, USA.
Glutathione S-transferases (GSTs) detoxify benzene oxide (BO), a carcinogen. GSTT1 and GSTP1 show significant activity, with GSTT1 being critical for BO detoxification, while GSTA1 and GSTM1 appear less important.
Area of Science:
- Biochemistry
- Toxicology
- Enzymology
Background:
- Benzene is a human carcinogen requiring activation to benzene oxide (BO).
- Detoxification of BO occurs via glutathione conjugation, producing S-phenylmercapturic acid.
- Glutathione S-transferases (GSTs) may catalyze this detoxification, but kinetic data are lacking.
Purpose of the Study:
- To investigate the kinetic parameters of specific GST isoforms (GSTA1, GSTT1, GSTM1, GSTP1) in catalyzing the reaction between glutathione and benzene oxide (BO).
- To determine the role of different GSTs in the detoxification pathway of BO.
Main Methods:
- Incubation of GSTA1, GSTT1, GSTM1, and GSTP1 with glutathione and benzene oxide (BO).
- Quantification of S-phenylglutathione formation.
- Determination of kinetic parameters (Km and Vmax) for active GST isoforms.
Main Results:
- GSTT1 and GSTP1 exhibited measurable activity in catalyzing the glutathione conjugation of BO.
- Kinetic parameters for GSTT1 were Km = 420 μM and Vmax = 450 fmol/s.
- Kinetic parameters for GSTP1 were Km = 3600 μM and Vmax = 3100 fmol/s.
- GSTA1 and GSTM1 showed insufficient activity for kinetic analysis.
Conclusions:
- GSTT1 is a critical enzyme in the detoxification of benzene oxide (BO).
- GSTP1 also plays a significant role in BO detoxification.
- GSTA1 and GSTM1 appear to be less important in this detoxification pathway.
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