Related Experiment Video
Updated: Jul 13, 2026
14:57
Spectrophotometric Screening for Potential Inhibitors of Cytosolic Glutathione S-Transferases
Published on: October 10, 2020
Modulation of human glutathione s-transferases by polyphenon e intervention
H-H Sherry Chow1, Iman A Hakim, Donna R Vining
1Arizona Cancer Center, The University of Arizona, Tucson, AZ 85724, USA. schow@azcc.arizona.edu
Summary
Green tea polyphenols boost detoxification enzymes, particularly in individuals with lower baseline activity. This suggests a mechanism for green tea
Area of Science:
- Biochemistry
- Nutritional Science
- Cancer Prevention
Background:
- Green tea consumption is linked to reduced cancer risk.
- Induction of detoxification enzymes is a proposed mechanism.
- Glutathione S-transferases (GST) are key detoxification enzymes.
Purpose of the Study:
- To investigate the effect of green tea polyphenols on GST activity and levels.
- To determine if green tea polyphenols can enhance detoxification capacity.
Main Methods:
- 42 healthy volunteers underwent a 4-week washout period.
- Baseline GST activity and levels were measured in plasma and lymphocytes.
- Participants consumed 800 mg of epigallocatechin gallate (EGCG) from Polyphenon E daily for 4 weeks.
- Post-intervention GST assessment was performed.
Main Results:
- Polyphenon E increased GST activity in lymphocytes (P=0.058).
- Significant GST activity increase (80%) observed in the lowest baseline tertile (P=0.004).
- GST-pi levels in lymphocytes significantly increased, especially in the lowest baseline tertile (P=0.003).
- Minimal effects on GST-mu and plasma GST-alpha levels were noted.
Conclusions:
- Green tea polyphenol administration differentially affects GST based on baseline levels.
- GST activity and GST-pi levels were significantly elevated in individuals with low baseline activity.
- Green tea intervention may enhance carcinogen detoxification in those with lower baseline capacity.
Related Concept Videos
01:22Phase II Reactions: Glutathione Conjugation and Mercapturic Acid Formation
Glutathione, a tripeptide made up of glutamate, cysteine, and glycine, is a critical player in the detoxification of drugs and xenobiotics via a process known as glutathione conjugation or mercapturic acid formation. This phase II biotransformation reaction involves the covalent binding of glutathione to a drug or its metabolite, enhancing the compound's water solubility and enabling its excretion.
Several distinctive characteristics distinguish glutathione conjugation from other phase II...
Several distinctive characteristics distinguish glutathione conjugation from other phase II...
01:27Pharmacogenetics of Phase II Enzymes: N-acetyltransferase, Thiopurine S-methyltransferase, UDP-glucuronosyltransferase
Phase II biotransformation reactions are essential for detoxifying and eliminating xenobiotics, including many pharmaceutical compounds. These reactions typically involve conjugation, the covalent attachment of polar endogenous groups such as glucuronic acid, sulfate, methyl, or acetyl moieties to functional groups introduced during Phase I metabolism. The resulting conjugates are more water-soluble, enabling efficient renal or biliary excretion.The major classes of Phase II enzymes include...
01:11Pharmacogenetics of Drug Targets: β₂-Adrenergic Receptors, Apo E, Thymidylate Synthase
Genetic polymorphisms in drug targets have emerged as critical determinants of interindividual variability in drug response and toxicity. Pharmacogenomic investigations increasingly focus on identifying these variations to personalize and optimize therapeutic interventions. A drug target may be a receptor, enzyme, or signaling protein involved in pharmacologic responses or disease-related pathways. While early pharmacogenetic studies focused primarily on drug metabolism, current research...
01:29Pharmacogenetic Phenotypes: Alterations in Pharmacokinetics, Drug Targets and Biologic Milieu
Genetic variations significantly influence drug response through pharmacokinetics, receptor interactions, and biologic milieu modifications. Pharmacokinetic alterations impact drug metabolism and clearance, affecting efficacy and toxicity. Variants in drug-metabolizing enzymes, such as CYP2C9 and CYP2C19, alter drug activation and elimination. For example, CYP2C9 loss-of-function variants require lower warfarin doses to prevent excessive bleeding, while CYP2C19 variants reduce clopidogrel...
01:27Pharmacogenetics of Drug Metabolism: Overview
Genetic polymorphism in drug metabolism is crucial to the inter-individual variability observed in drug responses. Drug metabolism primarily involves the chemical modification of drugs and other xenobiotics to enhance their elimination by increasing their polarity. Two main classes of enzymes mediate this biotransformation process: Phase I enzymes, primarily cytochrome P450s, catalyze oxidation and reduction reactions, while other enzymes, such as esterases, mediate hydrolysis, and Phase II...
01:25Bioactivation and Tissue Toxicity
Bioactivation is a metabolic process that transforms less reactive substances into highly reactive metabolites, initiating tissue toxicity. This transformation can lead to various toxic effects, including carcinogenesis and teratogenesis. Reactive metabolites are classified into two main types: electrophiles and free radicals.Electrophiles are electron-deficient species and are produced primarily by the enzyme cytochrome P-450 during the metabolism of compounds containing carbon, nitrogen, or...