PARENT SESSION
PW1 - Molecular/ Cellular Toxicology
Wednesday, 20 November 2002
8:00 AM to 6:30 PM
Exhibit Hall

(P705) Conservation of a glutathione S-transferase that provides protection against oxidative injury in largemouth bass.

Gallagher, Evan^*,1, Pham, Robert¹, Doi, Adriana², Hughes, Erin¹, ¹ Dept of Physiological Sciences, University of Florida, Gainesville, Fl² National Institute of Environmental Health Sciences, Research Triangle Park, NC

ABSTRACT- We are currently investigating the role of detoxification pathways in protecting against the sublethal effects of chemicals in largemouth bass (Micropterus salmoides), a higher order predatory game fish found throughout the United States. Our early studies indicated a remarkable ability of bass liver glutathione S-transferases (GSTs) to detoxify 4-hydroxy-2-nonenal (4HNE), a common mutagenic and cytotoxic aldehyde produced during the peroxidation of lipids. Bass liver GST-mediated 4HNE conjugation follows high efficiency single-enzyme Michaelis-Menten kinetics, suggesting that an individual GST isoform is involved in 4HNE detoxification. A full-length GST cDNA of 957 base pairs (bp) in length, containing an open reading frame of 666 bp and encoding a polypeptide of 222 amino acids has been isolated. The recombinant expressed protein showed high catalytic activity towards 4HNE, and HPLC-GST subunit analysis followed by sequencing demonstrated that the isolated bass liver GST subunit constitutes the major GST protein in bass liver. Interestingly, a BLAST homology search revealed the presence of homologous GST proteins in plaice (Pleuronectes platessa), fathead minnow (Pimelphales promelas), and European flounder (Platichthys flesus), but not in mammals. In summary, the presence of a highly expressed GST isozyme in bass and evolutionarily divergent species indicates the conservation of an important protein in protection against oxidative damage in aquatic species. Our results also underscore the importance of isozyme analysis when assessing the ability of fish to detoxify toxicologically relevant substrates through multigenic biochemical pathways. Supported by NIH P42 ES07375.

Key words: glutathione S-transferse, 4-hydroxynonenal, cloning, largemouth bass