Glutathione S-transferase as a biomarker in the Antarctic bivalve Laternula ellipticaafter exposure to the polychlorinated biphenyl mixture Aroclor 1254

摘要

Glutathione S-transferases (GSTs) are a family of multifunctional enzymes involved in cellular detoxificationthat catalyze the attachment of electrophilic substrates to glutathione. Two classes of GSTs related to the rhoand sigma classes of enzymes in Antarctic bivalves have been cloned from Laternula elliptica. The full-lengthcDNA of rho class GST (leGSTr) is 1530 bp in length and contains an open reading frame (ORF) of 672 bpencoding 223 amino acid residues. The deduced amino acid sequences of this gene have 41% and 40% identityto rho class GSTs from Ctenopharyngodon idella and Pleuronectes platessa, respectively. The sigma class GST(leGSTs) cDNA, however, is 1127 bp in length and contains an ORF of 696 bp encoding 231 amino acidresidues. The deduced amino acid sequences share only 22% identity with sigma class GST from Xenopuslaevis. The transcriptional expression of leGSTr, leGSTs, and leGSTp cloned in our previous study wereexamined using real-time polymerase chain reaction in response to exposure to a polychlorinated biphenyl(PCB) mixture. The expressions of these three GST transcripts were rapidly upregulated, although theyshowed different expression levels and patterns within each isoform. Moreover, leGSTs was the mostupregulated in the gill and digestive gland in response to PCB exposure. The recombinant GSTs were highlyexpressed in transformed Escherichia coli, and their kinetic properties were studied with various substrates.As a result, the three classes of GSTs were found to have diverse biological functions and were responsible fordifferent enzymatic features.