Characterization of the Omega Class of Glutathione Transferases

Whitbread, Astrid K.; Masoumi, Amir; Tetlow, Natasha; Schmuck, Erica; Coggan, Marjorie; Board, Philip G.

doi:10.1016/s0076-6879(05)01005-0

Cited by 198 publications

(192 citation statements)

References 62 publications

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“…S1B), which increased confidence in the spectral annotation. Interestingly, Cys476 on CYP27A1 has been reported to be important for binding of the heme group to this enzyme (51) and Cys32 on GSTO1 is the known active site cysteine residue (52). These adduct site localizations suggested that adduction of these proteins may impact enzymatic activity.…”

Section: Resultsmentioning

confidence: 99%

Specificity of Protein Covalent Modification by the Electrophilic Proteasome Inhibitor Carfilzomib in Human Cells

Federspiel

Codreanu

Goyal

et al. 2016

Molecular & Cellular Proteomics

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Carfilzomib (CFZ) is a second-generation proteasome inhibitor that is Food and Drug Administration and European Commission approved for the treatment of relapsed or refractory multiple myeloma. CFZ is an epoxomicin derivative with an epoxyketone electrophilic warhead that irreversibly adducts the catalytic threonine residue of the ␤5 subunit of the proteasome. Although CFZ produces a highly potent, sustained inactivation of the proteasome, the electrophilic nature of the drug could potentially produce off-target protein adduction. To address this possibility, we synthesized an alkynyl analog of CFZ and investigated protein adduction by this analog in HepG2 cells. Using click chemistry coupled with streptavidin based IP and shotgun tandem mass spectrometry (MS/MS), we identified two off-target proteins, cytochrome P450 27A1 (CYP27A1) and glutathione S-transferase omega 1 (GSTO1), as targets of the alkynyl CFZ probe. We confirmed the adduction of CYP27A1 and GSTO1 by streptavidin capture and immunoblotting methodology and then site-specifically mapped the adducts with targeted MS/MS methods. Although CFZ adduction of CYP27A1 and GSTO1 in vitro decreased the activities of these enzymes, the small fraction of these proteins modified by CFZ in intact cells should limit the impact of these offtarget modifications. The data support the high selectivity of CFZ for covalent modification of its therapeutic targets, despite the presence of a reactive electrophile. The approach we describe offers a generalizable method to evaluate the safety profile of covalent protein-modifying

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Section: Resultsmentioning

confidence: 99%

Specificity of Protein Covalent Modification by the Electrophilic Proteasome Inhibitor Carfilzomib in Human Cells

Federspiel

Codreanu

Goyal

et al. 2016

Molecular & Cellular Proteomics

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“…Recently, a number of mechanisms have been elucidated for the two-electron reduction of dehydroascorbate (DHA) to Vitamin C in animals. This conversion can take place via a glutathione (GSH)-dependent mechanism catalyzed by glutaredoxin, protein disulfide isomerase, and glutathione transferases or by NADPH-dependent mechanisms including reduction catalyzed by 3α-hydroxysteroid dehydrogenase (9)(10)(11)(12). In turn, GSH levels are maintained by the NADPH-dependent reduction of oxidized glutathione (GSSG) (13) (Fig.…”

Section: Mri | Molecular Imaging | Probe | Kineticsmentioning

confidence: 99%

“…Here we report the development of [1- 13 C] dehydroascorbate [DHA], the oxidized form of Vitamin C, as an endogenous redox sensor for in vivo imaging using hyperpolarized 13 C spectroscopy. In murine models, hyperpolarized [1-13 C] DHA was rapidly converted to [1][2][3][4][5][6][7][8][9][10][11][12][13] C] vitamin C within the liver, kidneys, and brain, as well as within tumor in a transgenic prostate cancer mouse. This result is consistent with what has been previously described for the DHA/Vitamin C redox pair, and points to a role for hyperpolarized [1][2][3][4][5][6][7][8][9][10][11][12][13] C] DHA in characterizing the concentrations of key intracellular reducing agents, including GSH.…”

mentioning

confidence: 99%

Hyperpolarized ¹³ C dehydroascorbate as an endogenous redox sensor for in vivo metabolic imaging

Keshari

Kurhanewicz

Bok

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

151

159

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Reduction and oxidation (redox) chemistry is involved in both normal and abnormal cellular function, in processes as diverse as circadian rhythms and neurotransmission. Intracellular redox is maintained by coupled reactions involving NADPH, glutathione (GSH), and vitamin C, as well as their corresponding oxidized counterparts. In addition to functioning as enzyme cofactors, these reducing agents have a critical role in dealing with reactive oxygen species (ROS), the toxic products of oxidative metabolism seen as culprits in aging, neurodegenerative disease, and ischemia/ reperfusion injury. Despite this strong relationship between redox and human disease, methods to interrogate a redox pair in vivo are limited. Here we report the development of [1-13 C] dehydroascorbate [DHA], the oxidized form of Vitamin C, as an endogenous redox sensor for in vivo imaging using hyperpolarized 13 C spectroscopy. In murine models, hyperpolarized [1-13 C] DHA was rapidly converted to [1-13 C] vitamin C within the liver, kidneys, and brain, as well as within tumor in a transgenic prostate cancer mouse. This result is consistent with what has been previously described for the DHA/Vitamin C redox pair, and points to a role for hyperpolarized [1-13 C] DHA in characterizing the concentrations of key intracellular reducing agents, including GSH. More broadly, these findings suggest a prognostic role for this new redox sensor in determining vulnerability of both normal and abnormal tissues to ROS.MRI | molecular imaging | probe | kinetics

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“…The presence of an active-site cysteine residue differs significantly from the tyrosine or serine residue found in the active site of other mammalian cytosolic GSTs (2). Both human omega-class GSTs exhibit thioltransferase, dehydroascorbate reductase, and monomethylarsonate (V) reductase activities that are dependent on an active-site cysteine residue (3). These reactions are not catalyzed by other GST classes, and the dehydroascorbate reductase activity of GSTO2-2 is high, indicating that this may be its primary physiological function (6).…”

Section: Introductionmentioning

confidence: 98%

“…The recently identified omega-class glutathione transferases (GSTs) are widely distributed across a range of species from Caenorhabditis elegans to humans (2,3). Two human omega-class genes have been characterized, and their RNA and protein (GSTO1-1 and GSTO2-2) products have been identified in multiple tissues (4).…”

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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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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Characterization of the Omega Class of Glutathione Transferases

Cited by 198 publications

References 62 publications

Specificity of Protein Covalent Modification by the Electrophilic Proteasome Inhibitor Carfilzomib in Human Cells

Specificity of Protein Covalent Modification by the Electrophilic Proteasome Inhibitor Carfilzomib in Human Cells

Hyperpolarized ¹³ C dehydroascorbate as an endogenous redox sensor for in vivo metabolic imaging

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

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Characterization of the Omega Class of Glutathione Transferases

Cited by 198 publications

References 62 publications

Specificity of Protein Covalent Modification by the Electrophilic Proteasome Inhibitor Carfilzomib in Human Cells

Specificity of Protein Covalent Modification by the Electrophilic Proteasome Inhibitor Carfilzomib in Human Cells

Hyperpolarized 13 C dehydroascorbate as an endogenous redox sensor for in vivo metabolic imaging

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

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Hyperpolarized ¹³ C dehydroascorbate as an endogenous redox sensor for in vivo metabolic imaging