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C-terminal, alpha helical domain of Class Zeta Glutathione S-transferases Glutathione S-transferase (GST) C-terminal domain family, Class Zeta subfamily; GSTs are cytosolic dimeric proteins involved in cellular detoxification by catalyzing the conjugation of glutathione (GSH) with a wide range of endogenous and xenobiotic alkylating agents, including carcinogens, therapeutic drugs, environmental toxins, and products of oxidative stress. The GST fold contains an N-terminal thioredoxin-fold domain and a C-terminal alpha helical domain, with an active site located in a cleft between the two domains. GSH binds to the N-terminal domain while the hydrophobic substrate occupies a pocket in the C-terminal domain. Class Zeta GSTs, also known as maleylacetoacetate (MAA) isomerases, catalyze the isomerization of MAA to fumarylacetoacetate, the penultimate step in tyrosine/phenylalanine catabolism, using GSH as a cofactor. They show little GSH-conjugating activity towards traditional GST substrates, but display modest GSH peroxidase activity. They are also implicated in the detoxification of the carcinogen dichloroacetic acid by catalyzing its dechlorination to glyoxylic acid.
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