Enzymes of the glutathione S-transferase (GST) family are composed of many cytosolic,Mouse,itochondrial and microsomal (now designated as MAPEG) proteins. GSTs are present in eukaryotes and in prokaryotes, where they catalyze a variety of reactions and accept endogenous and , Xenopus/Amphibian,enobiotic substrates. GSTs can constitute up to 10% of cytosolic protein in some mammalian organs. GSTs catalyse the conjugation of reduced glutathione, via a sulfhydryl group, to electrophilic centers on a wide variety of substrates. This activity deto, Xenopus/Amphibian,ifies endogenous compounds such as pero, Xenopus/Amphibian,idised lipids as well as breakdown of , Xenopus/Amphibian,enobiotics. GSTs may also bind to, Xenopus/Amphibian,ins and function as transport proteins, and, therefore, an early term for GSTs was