Thiol-mediated NTA-Fe(III) reduction and lipid peroxidation.
The nephrotoxicity of nitrilotriacetate chelated Fe(III) (NTA-Fe(III)) has been linked to the metabolism of glutathione (GSH) by gamma-glutamyl transpeptidase and a dipeptidase. The products of these enzymes are cysteinyl-glycine (cys-gly) and cysteine (cys), which are proposed to be the reductants of NTA-Fe(III) to cause oxidative damage to various biomolecules. The ability of cys-gly and cys to cause in vitro NTA-Fe(III)-dependent lipid peroxidation correlated directly with their ability to reduce NTA-Fe(III). GSH reduced iron at a much slower rate and did not stimulate lipid peroxidation. It has been proposed that GSH, cys-gly and cys reduce iron at different rates because their thiols have different pKas. However, increasing the amount of GS-, by raising the pH, did not cause a corresponding increase in the rate of iron reduction. The monomethyl ester of GSH reduced NTA-Fe(III) at the same rate as GSH, but the dimethyl ester of GSH reduced NTA-Fe(III) approximately 30 times faster. From this we conclude that GSH does not reduce NTA-Fe(III) at the same rate as cys-gly and cys because of the liganding between GSH and the iron.
Biotechnology Center, Utah State University, Logan 84322-4705.
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D002273:Carcinogens / Q000737:chemistry*; D003545:Cysteine / Q000737:chemistry; D004151:Dipeptides / Q000737:chemistry; D005290:Ferric Compounds / Q000737:chemistry*; D005978:Glutathione / Q000737:chemistry; D007477:Ions; D008024:Ligands; D015227:Lipid Peroxidation; D009571:Nitrilotriacetic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D013438:Sulfhydryl Compounds / Q000737:chemistry*
D002273:Carcinogens; D004151:Dipeptides; D005290:Ferric Compounds; D007477:Ions; D008024:Ligands; D013438:Sulfhydryl Compounds; C028505:cysteinylglycine; D005978:Glutathione; D003545:Cysteine; D009571:Nitrilotriacetic Acid; C020326:ferric nitrilotriacetate