A comprehensive analysis of the NADP-malic enzyme gene family of Arabidopsis.
The Arabidopsis (Arabidopsis thaliana) genome contains four genes encoding putative NADP-malic enzymes (MEs; AtNADP-ME1-ME4). 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.
Wheeler
Mariel C Gerrard
MC
Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI), Universidad Nacional de Rosario, Argentina.
Tronconi
Marcos A
MA
Drincovich
María F
MF
Andreo
Carlos S
CS
Flügge
Ulf-Ingo
UI
Maurino
Verónica G
VG
D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology* / Q000235:genetics*; D003001:Cloning, Molecular; D019295:Computational Biology; D035264:Flowers / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D018525:Germination; D007527:Isoenzymes / Q000235:genetics; D008291:Malate Dehydrogenase / Q000235:genetics / Q000378:metabolism; D005810:Multigene Family / Q000235:genetics*; D010802:Phylogeny; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D018520:Plant Shoots / Q000235:genetics / Q000378:metabolism; D018547:Plant Stems / Q000235:genetics / Q000378:metabolism; D018087:Plastids / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000378:metabolism
D007527:Isoenzymes; D008291:Malate Dehydrogenase; C031917:malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+)