Glutathione conjugation is considered to be an innate protective mechanism, developed to protect the body from potentially damaging electrophilic compounds. These compounds can either be directly occurring (e.g. naturally occurring/endogenous compound, or parent drug) or result from phase I metabolism reactions creating reactive electrophilic groups.
Glutathione is a water soluble antioxidant tripeptide compound, consisting of glycine, glutamic acid and cysteine molecules, synthesised de novo in mammalian cells.
It is an unusual peptide in that the peptide bond between the glutamate residue
and the cysteine residue is formed with the g-carboxylate group of the former rather
than the a-carboxylate group.
Glutathione acts as a non-specific reducing agent, thought to keep proteins in their reduced thiol form, thereby preventing cysteine residues from oxidizing and cross-linking with one another to form disulphide bridges.
Transferases are defined as enzymes that catalyse the transfer of one functional group from one molecule (donor) to another (acceptor). Glutathione-S-transferases
are a complex group of enzymes which mediate the conjugation of compounds with glutathione. These enzymes will be discussed further, including their many isoforms, complex and varied actions within the body, their induction, inhibition, and ultimately, their potential as therapeutic targets.