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A pathway for repair of NAD(P)H in plants

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Published in Journal of Biological Chemistry. 2014, vol. 289, no. 21, p. 14692-14706
Abstract Unwanted enzyme side reactions and spontaneous decomposition of metabolites can lead to a build-up of compounds that compete with natural enzyme substrates and must be dealt with for efficient metabolism. It has recently been realized that there are enzymes that process such compounds, formulating the concept of metabolite repair. NADH and NADPH are vital cellular redox cofactors but can form non-functional hydrates (named NAD(P)HX) spontaneously or enzymatically that compete with enzymes dependent on NAD(P)H, impairing normal enzyme function. Here we report on the functional characterization of components of a potential NAD(P)H repair pathway in plants comprising a stereospecific dehydratase (NNRD) and an epimerase (NNRE), the latter being fused to a vitamin B6 salvage enzyme. Through the use of the recombinant proteins, we show that the ATP-dependent NNRD and NNRE act concomitantly to restore NAD(P)HX to NAD(P)H. NNRD behaves as a tetramer and NNRE as a dimer, but the proteins do not physically interact. In vivo fluorescence analysis demonstrates that the proteins are localized to mitochondria and/or plastids, implicating these as the key organelles where this repair is required. Expression analysis indicates that whereas NNRE is present ubiquitously, NNRD is restricted to seeds but appears to be dispensable during the normal Arabidopsis life cycle.
Keywords Amino Acid SequenceArabidopsis/genetics/metabolismArabidopsis Proteins/chemistry/genetics/metabolismBlottingWesternGene Expression RegulationPlantHydro-Lyases/chemistry/genetics/metabolismLuminescent Proteins/genetics/metabolismMetabolic Networks and Pathways/geneticsMicroscopyConfocalMitochondria/metabolismModelsMolecularMolecular Sequence DataMolecular StructureMutationNAD/chemistry/metabolismNADP/chemistry/metabolismPlantsGenetically ModifiedPlastids/metabolismProtein StructureTertiaryRacemases and Epimerases/chemistry/genetics/metabolismReverse Transcriptase Polymerase Chain ReactionSequence HomologyAmino Acid
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PMID: 24706747
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COLINAS MARTINEZ, Maite Felicitas et al. A pathway for repair of NAD(P)H in plants. In: Journal of Biological Chemistry, 2014, vol. 289, n° 21, p. 14692-14706. https://archive-ouverte.unige.ch/unige:89266

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Deposited on : 2016-11-22

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