The NADPH:quinone oxidoreductase P1-zeta-crystallin in Arabidopsis catalyzes the alpha,beta-hydrogenation of 2-alkenals: detoxication of the lipid peroxide-derived reactive aldehydes.
P1-zeta-crystallin (P1-ZCr) is an oxidative stress-induced NADPH:quinone oxidoreductase in Arabidopsis thaliana, but its physiological electron acceptors have not been identified. We found that recombinant P1-ZCr catalyzed the reduction of 2-alkenals of carbon chain C(3)-C(9) with NADPH. Among these 2-alkenals, the highest specificity was observed for 4-hydroxy-(2E)-nonenal (HNE), one of the major toxic products generated from lipid peroxides. (3Z)-Hexenal and aldehydes without alpha,beta-unsaturated bonds did not serve as electron acceptors. In the 2-alkenal molecules, P1-ZCr catalyzed the hydrogenation of alpha,beta-unsaturated bonds, but not the reduction of the aldehyde moiety, to produce saturated aldehydes, as determined by gas chromatography/mass spectrometry. We propose the enzyme name NADPH:2-alkenal alpha,beta-hydrogenase (ALH). A major portion of the NADPH-dependent HNE-reducing activity in A. thaliana leaves was inhibited by the specific antiserum against P1-ZCr, indicating that the endogenous P1-ZCr protein has ALH activity. Because expression of the P1-ZCr gene in A. thaliana is induced by oxidative stress treatments, we conclude that P1-ZCr functions as a defense against oxidative stress by scavenging the highly toxic, lipid peroxide-derived alpha,beta-unsaturated aldehydes.
Mano
Jun'ichi
J
Faculty of Agriculture, Yamaguchi University, Yoshida 1677-1, Yamaguchi, 753-8515 Japan. mano@agr.yamaguchi-u.ac.jp
Torii
Yoshimitsu
Y
Hayashi
Shun-ichiro
S
Takimoto
Koichi
K
Matsui
Kenji
K
Nakamura
Kaoru
K
Inzé
Dirk
D
Babiychuk
Elena
E
Kushnir
Sergei
S
Asada
Kozi
K
D000429:Alcohol Oxidoreductases / Q000378:metabolism; D000449:Aldehyde Reductase; D000447:Aldehydes / Q000378:metabolism; D000074408:Aldo-Keto Reductases; D000475:Alkenes / Q000378:metabolism*; D017360:Arabidopsis / Q000378:metabolism*; D002384:Catalysis; D004579:Electron Transport; D008401:Gas Chromatography-Mass Spectrometry; D005982:Glutathione Transferase / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006865:Hydrogenation; D015227:Lipid Peroxidation; D008956:Models, Chemical; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D038226:zeta-Crystallins / Q000378:metabolism*
D000447:Aldehydes; D000475:Alkenes; D011994:Recombinant Proteins; D038226:zeta-Crystallins; C045934:4-hydroxy-2-hexenal; D000429:Alcohol Oxidoreductases; D000074408:Aldo-Keto Reductases; D000449:Aldehyde Reductase; D016660:NAD(P)H Dehydrogenase (Quinone); D005982:Glutathione Transferase; C027576:4-hydroxy-2-nonenal