4: Examples of glutathione-S-transferase (GST)mediated and glutathione (GSH)-dependent reactions that do not result in the formation of GSH conjugates as end products. (a) GST functioning as a glutathione peroxidase, using GSH to reduce an organic hydroperoxide (ROOH) to the monohydroxy alcohol (ROH). (b) A zeta GST catalysing a cis-trans isomerisation of maleylaceto-acetate to fumarylacetoacetate. (c) GST catalysing the isomeri-sation of a thiadiazolidine