title: Inactivation of glutathione reductase by 4-hydroxynonenal and other endogenous aldehydes.
abstract: 4-Hydroxynonenal, a product of oxidative degradation of unsaturated lipids, is an endogenous reactive alpha,beta-unsaturated aldehyde with numerous biological activities. 4-Hydroxynonenal rapidly inactivated glutathione reductase in an NADPH-dependent reaction. Inactivation appears to involve the initial formation of an enzyme-inactivator complex, K(D) = 0.5 microM, followed by the inactivation reaction, k = 1.3 x 10(-2) min(-1). alpha,beta-Unsaturated aldehydes such as acrolein, crotonaldehyde, and cinnamaldehyde also inactivated glutathione reductase, although rates varied widely. Inactivation of glutathione reductase by alpha,beta-unsaturated aldehydes was followed by slower NADPH-independent reactions that led to formation of nonfluorescent cross-linked products, accompanied by loss of lysine and histidine residues. Other reactive endogenous aldehydes such as methylglyoxal, 3-deoxyglucosone, and xylosone inactivated glutathione reductase by an NADPH-independent mechanism, with methylglyoxal being the most reactive. However, 2-oxoaldehydes were much less effective than 4-hydroxynonenal. Inactivation of glutathione reductase by these 2-oxoaldehydes was followed by slower reactions that led to the formation of fluorescent cross-linked products over a period of several weeks. These changes were accompanied by loss of arginine residues. Thus, the sequence of events is different for inactivation and modification of glutathione reductase by alpha,beta-unsaturated aldehydes compared with 2-oxoaldehydes with respect to kinetics, NADPH requirements, fluorescence changes, and loss of amino acid residues. The ability of 4-hydroxynonenal at low concentrations to inactivate glutathione reductase, a central antioxidant enzyme, suggests that oxidative degradation of unsaturated lipids may initiate a positive feedback loop that enhances the potential for oxidative damage.
authors.affiliation: Department of Biochemistry, University of New Mexico, School of Medicine, Albuquerque 87131, U.S.A.
authors.forename: D L
authors.initials: DL
authors.lastname: Vander Jagt
authors.forename: L A
authors.initials: LA
authors.lastname: Hunsaker
authors.forename: T J
authors.initials: TJ
authors.lastname: Vander Jagt
authors.forename: M S
authors.initials: MS
authors.lastname: Gomez
authors.forename: D M
authors.initials: DM
authors.lastname: Gonzales
authors.forename: L M
authors.initials: LM
authors.lastname: Deck
authors.forename: R E
authors.initials: RE
authors.lastname: Royer
mesh_terms: D000171:Acrolein / Q000031:analogs & derivatives / Q000494:pharmacology; D000447:Aldehydes / Q000378:metabolism / Q000494:pharmacology*; D000596:Amino Acids / Q000032:analysis; D003847:Deoxyglucose / Q000031:analogs & derivatives / Q000494:pharmacology; D004789:Enzyme Activation; D005980:Glutathione Reductase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D007661:Ketoses / Q000494:pharmacology; D011765:Pyruvaldehyde / Q000494:pharmacology; D013050:Spectrometry, Fluorescence
chemical_list: D000447:Aldehydes; D000596:Amino Acids; D007661:Ketoses; C067906:threo-pentos-2-ulose; D011765:Pyruvaldehyde; D000171:Acrolein; D003847:Deoxyglucose; C012796:2-butenal; D005980:Glutathione Reductase; C016350:3-deoxyglucosone; C027576:4-hydroxy-2-nonenal; C012843:cinnamaldehyde