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C-terminal, alpha helical domain of Class Phi Glutathione S-transferases Glutathione S-transferase (GST) C-terminal domain family, Class Phi subfamily; composed of plant-specific class Phi GSTs and related fungal and bacterial proteins. 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. The class Phi GST subfamily has experience extensive gene duplication. The Arabidopsis and Oryza genomes contain 13 and 16 Tau GSTs, respectively. They are primarily responsible for herbicide detoxification together with class Tau GSTs, showing class specificity in substrate preference. Phi enzymes are highly reactive toward chloroacetanilide and thiocarbamate herbicides. Some Phi GSTs have other functions including transport of flavonoid pigments to the vacuole, shoot regeneration and GSH peroxidase activity.
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