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First published online August 19, 2005; 10.1104/pp.105.065953 Plant Physiology 139:39-51 (2005) © 2005 American Society of Plant Biologists A Comprehensive Analysis of the NADP-Malic Enzyme Gene Family of Arabidopsis1,[w]Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI), Universidad Nacional de Rosario, Rosario, Argentina (M.C.G.W., M.A.T., M.F.D., C.S.A.); and Botanisches Institut, Universität zu Köln, D50931 Cologne, Germany (U.-I.F., V.G.M.)
The Arabidopsis (Arabidopsis thaliana) genome contains four genes encoding putative NADP-malic enzymes (MEs; AtNADP-ME1ME4). NADP-ME4 is localized to plastids, whereas the other three isoforms do not possess any predicted organellar targeting sequence and are therefore expected to be cytosolic. The plant NADP-MEs can be classified into four groups: groups I and II comprising cytosolic and plastidic isoforms from dicots, respectively; group III containing isoforms from monocots; and group IV composed of both monocots and dicots, including AtNADP-ME1. AtNADP-MEs contained all conserved motifs common to plant NADP-MEs and the recombinant isozymes showed different kinetic and structural properties. NADP-ME2 exhibits the highest specific activity, while NADP-ME3 and NADP-ME4 present the highest catalytic efficiency for NADP and malate, respectively. NADP-ME4 exists in equilibrium of active dimers and tetramers, while the cytosolic counterparts are present as hexamers or octamers. Characterization of T-DNA insertion mutant and promoter activity studies indicates that NADP-ME2 is responsible for the major part of NADP-ME activity in mature tissues of Arabidopsis. Whereas NADP-ME2 and -ME4 are constitutively expressed, the expression of NADP-ME1 and NADP-ME3 is restricted by both developmental and cell-specific signals. These isoforms may play specific roles at particular developmental stages of the plant rather than being involved in primary metabolism.
1 This work was supported by the Agencia Nacional de Promoción Científica y Tecnológica (PICT 111604, Argentina), Fundación Antorchas (project no. 424863, Argentina), SeCyt-DAAD (DA/PA05BI/016), and CONICET (PIP 3029) as well as the Deutsche Forschungsgemeinschaft (to V.G.M.). [w] The online version of this article contains Web-only data. Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.105.065953. * Corresponding author; e-mail candreo{at}fbioyf.unr.edu.ar; fax 543414370044. Received May 19, 2005; returned for revision June 13, 2005; accepted June 13, 2005. This article has been cited by other articles:
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