Nucleophilic attack, glutathione conjugation

TABLE 12.4. Glutathione 5-Transferase-Mediated Conjugations Involving Nucleophilic Displacement, Michael Addition, and Nucleophilic Attack on Strained Oxirange Rings... 

Natural acryloyl compounds can also undergo CTI catalyzed by enzymatic systems. In this way, the CTI of maleylacetoacetate, a degradation product of phenylalanine and tyrosine, to fumarylacetoacetate was achieved by the cis-trans isomer-ase glutathione system. The reaction seems to involve a nucleophilic attack at the C2 carbon rather than a conjugated addition and the subsequent rotation of the single bond [58]. 

The glutathione 5-transferases catalyze numerous reactions in which the glutathione thiolate anion (GS ) serves as a nucleophile (A20, G11, J2). Thus the fundamental catalytic action of GST is to facilitate the formation or stabilization of GS , which can, in turn, attack electrophilic carbon, nitrogen, sulfur, or oxygen atoms contained in any xenobiotic. Literally hundreds of different compounds exist that contain a carbon atom sufficiently electrophilic to be able to react with GS" and form thioether conjugates. Thioether formation has been widely studied since the earliest convenient spectrophotmetric assays represented this type of reaction for example, the conjugation of GSH with l-chloro-2,4-dinitrobenzene, 1,2-dichloro-... 

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