4-hydroxynonenal inhibits Na(+)-K(+)-ATPase.
4-Hydroxynonenal binds rapidly to Na(+)-K(+)-ATPase, and this was accompanied by a decrease in measurable sulfhydryl groups and a loss of enzyme activity. The I50 value for Na(+)-K(+)-ATPase inhibition by 4-hydroxynonenal was found to be 120 microM. Although the sulfhydryl groups could be completely restored with beta-mercaptoethanol during the reaction of the Na(+)-K(+)-ATPase-HNE-adduct, the Na(+)-K(+)-ATPase activity was only partially restored by this reducing agent. A combination of hydroxylamine and beta-mercaptoethanol yielded the greatest recovery of enzyme activity, 85% of original. Thus, 4-hydroxynonenal binding to Na(+)-K(+)-ATPase led to an irreversible decrease of enzyme activity under the conditions employed. It is hypothesized that 4-hydroxynonenal reacts with sulfhydryls at sites on the enzyme that are inaccessible by beta-mercaptoethanol. Furthermore, evidence was obtained that 4-hydroxynonenal reacts with other amino acids such as lysine to form adducts that also interfere with protein function.
Siems
W G
WG
Department of Chemistry and Biochemistry, Montana State University, Bozeman 59717, USA.
Hapner
S J
SJ
van Kuijk
F J
FJ
D000447:Aldehydes / Q000494:pharmacology*; D002462:Cell Membrane / Q000201:enzymology; D003432:Cross-Linking Reagents; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007700:Kinetics; D008623:Mercaptoethanol / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D010084:Oxidation-Reduction; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*; D013438:Sulfhydryl Compounds
D000447:Aldehydes; D003432:Cross-Linking Reagents; D004791:Enzyme Inhibitors; D013438:Sulfhydryl Compounds; D010042:Ouabain; D008623:Mercaptoethanol; D000254:Sodium-Potassium-Exchanging ATPase; C027576:4-hydroxy-2-nonenal