ABSTRACT
Glutathione S-transferases (GST) are a family of isoenzymes involved in the binding, transport, and metabolism of xenobiotics and endogenous substances. Compounds with an electrophilic center conjugate readily with glutathione. GSH S-conjugates are typically converted to mercap-turic acids; the γ-Glu moiety of the conjugate is removed, and the resulting cysteinylglycine conjugate is converted to the cysteine conjugate, which is N-acety-lated and then excreted. The pathway varies with different compounds and species. Several organs and the intestinal flora may also be involved. Certain GSTs were previously known as Iigands (which bind bilirubin, steroids, azo dyes, and certain carcinogens) and were thought to function in the transport of these compounds from blood plasma into liver cells. GSTs from liver are dimeric enzymes that can contain four types of subunits. Data summarized in this chapter agree with the rapid equilibrium, random sequential, bi-bi mechanism for human placental glutathione S-transferase.
