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tion. Glycine conjugates are the most common amino acid conjugates in animals
(Fig. 5.9). Conjugation with L-glutamine is most common in humans and other primates, but it seems to occur to a lesser extent in non-primates. Taurine, arginine,
asparagine, histidine, lysine, glutamate, aspartate, alanine and serine are the other
amino acid conjugates found in mammals (Parkinson et al. 2013).
Conjugation with Glutathione The tripeptide glutathione (GSH) is found in virtually all mammalian tissues (Fig. 5.10). The presence of a potent nucleophilic thiol
group helps glutathione function as a scavenger of harmful electrophilic compounds
ingested or produced by metabolism. Xenobiotics conjugated with glutathione are
either highly electrophilic as such or are first metabolized to an electrophilic product prior to conjugation. Conjugation with glutathione reduces drug toxicity that
results from the reaction of cellular nucleophiles with electrophilic metabolites. The
glutathione S-transferases (GSTs) are a family of enzymes that catalyse the conjuFig. 5.9 Conjugation with amino acids (glycine conjugation with benzoic acid)
Fig. 5.10 Conjugation
with glutathione
S. Sudhakaran et al.
tion. Glycine conjugates are the most common amino acid conjugates in animals
(Fig. 5.9). Conjugation with L-glutamine is most common in humans and other primates, but it seems to occur to a lesser extent in non-primates. Taurine, arginine,
asparagine, histidine, lysine, glutamate, aspartate, alanine and serine are the other
amino acid conjugates found in mammals (Parkinson et al. 2013).
Conjugation with Glutathione The tripeptide glutathione (GSH) is found in virtually all mammalian tissues (Fig. 5.10). The presence of a potent nucleophilic thiol
group helps glutathione function as a scavenger of harmful electrophilic compounds
ingested or produced by metabolism. Xenobiotics conjugated with glutathione are
either highly electrophilic as such or are first metabolized to an electrophilic product prior to conjugation. Conjugation with glutathione reduces drug toxicity that
results from the reaction of cellular nucleophiles with electrophilic metabolites. The
glutathione S-transferases (GSTs) are a family of enzymes that catalyse the conjuFig. 5.9 Conjugation with amino acids (glycine conjugation with benzoic acid)
Fig. 5.10 Conjugation
with glutathione
S. Sudhakaran et al.