A group of novel glutathione S-transferase isozymes showing high activity towards 4-hydroxy-2-nonenal are present in bovine ocular tissues.
Recently, a mouse glutathione S-transferase (GST) isozyme, mGSTA4-4, which belongs to a distinct group of GSTs has been characterized in our laboratory. During the present studies, Western blot analyses of bovine ocular tissues using the antibodies raised against the recombinant mGSTA4-4 obtained by expression in Escherichia coli revealed that the orthologs of mGSTA4-4 were present in cornea, retina, iris-ciliary body and sclera, but absent in lens. These novel GST isozymes of bovine ocular tissues were purified by immunoaffinity chromatography using the antibodies against rec-mGSTA4-4 and were designated as bGST 5.8 (their pI value being 5.8). Amino acid sequences of CNBr fragments of bGST 5.8 from cornea, sclera, retina and iris-ciliary body showed high degree of primary structure homologies with the corresponding regions of mGSTA4-4 indicating these bovine GST isozymes were distinct from the alpha. mu and pi group GSTs and were the newest members of the group of GSTs to which mGSTA4-4 belongs. There were significant differences among the amino acid sequences of bGST 5.8 of cornea and iris-ciliary body and retina suggesting presence of at least two closely related genes at bGST 5.8 locus. bGST 5.8 isozymes showed high activity toward 4-HNE (four-to-five-fold higher than that towards 1-chloro-2,4-dinitrobenzene), expressed GSH-peroxidase activity towards fatty acid hydroperoxides and phospholipid hydroperoxides, and showed GSH-conjugating activity towards fatty acid epoxides suggesting that these isozymes may play an important role in protection mechanism against the endogenous toxicants formed during lipid peroxidation.
Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston 77555.
S K
SK
Srivastava
S S
SS
Singhal
K K
KK
Bajpai
M
M
Chaubey
N H
NH
Ansari
Y C
YC
Awasthi
D000447:Aldehydes / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002417:Cattle; D005123:Eye / Q000201:enzymology*; D005982:Glutathione Transferase / Q000737:chemistry / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D013379:Substrate Specificity
D000447:Aldehydes; D007527:Isoenzymes; D005982:Glutathione Transferase; C027576:4-hydroxy-2-nonenal