The NADPH:Quinone Oxidoreductase P1-ζ-crystallin in Arabidopsis Catalyzes the α,β-Hydrogenation of 2-Alkenals: Detoxication of the Lipid Peroxide-Derived Reactive Aldehydes

Abstract

; P1-z-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 a,b -unsaturated bonds did not serve as electron acceptors. In the 2-alkenal molecules, P1-ZCr catalyzed the hydrogenation of a,b -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 a,b -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 a,b -unsaturated aldehydes.

Escherichia coli YqhD Exhibits Aldehyde Reductase Activity and Protects from the Harmful Effect of Lipid Peroxidation-derived Aldehydes

“…In this context, detoxification of K 2 TeO 3 and K 2 Cr 2 O 7 by E. coli (Table 3) corroborates our in vitro determinations and confirms that YqhD has aldehyde dehydrogenase activity on acrolein and MDA. Kinetic parameters determined for YqhD are consistent with those reported for a number of aldehyde dehydrogenases acting on reactive aldehydes produced by lipid peroxidation both in plant and mammalian cells (33,34). However, although our results strongly support the idea that the enzyme functions as an aldehyde reductase in vivo as well as in vitro, the possibility of YqhD using other, yet unknown substrates in addition to acetaldehyde, propanaldehyde, butanaldehyde, MDA, and acrolein cannot be excluded.…”

“…E. coli cultures entering the exponential growth phase or in the stationary phase as well have been shown to exhibit increased levels of aldehyde dehydrogenase activity (35). High aldehyde dehydrogenase activity has been also reported in cells exposed to stress conditions as low temperatures, salinity, UV radiation, and ROS elicitors (33). Thus, the increased TBAR content observed in E. coli ⌬yqhD could reflect a role of YqhD in maintaining safe levels of reactive aldehydes within the cell.…”

“…Some mechanistic insights have been communicated in Arabidopsis thaliana where a NADPH quinone oxidoreductase (P1-ZCR) has been involved in the detoxification of lipid peroxidation-derived reactive aldehydes (33). The authors proposed that this protein was part of a defense mechanism against oxidative stress by scavenging highly toxic lipid peroxidationderived unsaturated aldehydes as acrolein and 4-hydroxynonenal.…”

Biosynthesis of plant‐derived flavor compounds

“…Overexpression of the tomato ADH2 gene has led to improved flavor of the fruit by increasing the levels of alcohols, particularly 3Z-hexenol (Speirs et al, 1998). An acyltransferase catalyzes the formation of 3Z-hexenyl acetate from 3Z-hexenol and acetyl CoA, and 2-alkenal reductase can reduce 2E-hexenal to hexanal Mano et al, 2002). The reaction sequence leading from a-linolenic acid to the signaling molecule jasmonic acid involves the enzymes 13-LOX, allene oxide synthase, allene oxide cyclase and 12-oxo-phytodienoic acid reductase, followed by three successive b-oxidation steps (Figure 7) (Howe and Schilmiller, 2002;Li et al, 2005).…”

Significant improvement of stress tolerance in tobacco plants by overexpressing a stress-responsive aldehyde dehydrogenase gene from maize (Zea mays)

“…In plants, very few enzymatic pathways that reduce aldehyde accumulation have been defined. Two enzymes including soybean aldose/aldehyde reductase and Arabidopsis alkenal, a, b-hydrogenase have been shown to participate in the reduction of aldehydes (Oberschall et al 2000;Mano et al 2002). In rice, two acetaldehyde-oxidizing ALDHs (ALDH1a and ALDH2a) were characterized.…”