Maize recombinant non-C4 NADP-malic enzyme: A novel dimeric malic enzyme with high specific activity

Among the different isoforms of NADP-malic enzyme (NADP-ME) involved in a wide range of metabolic pathways in plants, the NADP-ME that participates in C4-photosynthesis is the most studied. In the present work, the expression in E. coli of a cDNA encoding for a maize non-photosynthetic NADP-ME is pr...

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Veröffentlicht in:Plant molecular biology 2004-05, Vol.55 (1), p.97-107
Hauptverfasser: Saigo, M, Bologna, F.P, Maurino, V.G, Detarsio, E, Andreo, C.S, Drincovich, M.F
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Sprache:eng
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Zusammenfassung:Among the different isoforms of NADP-malic enzyme (NADP-ME) involved in a wide range of metabolic pathways in plants, the NADP-ME that participates in C4-photosynthesis is the most studied. In the present work, the expression in E. coli of a cDNA encoding for a maize non-photosynthetic NADP-ME is presented. The recombinant NADP-ME thus obtained presents kinetic and structural properties different from the enzyme previously purified from etiolated leaves and roots. Moreover, the recombinant non-photosynthetic NADP-ME presents very high intrinsic NADP-ME activity, which is unexpected for a non-C4 NADP-ME. Using antibodies against this recombinant enzyme, an immunoreactive band of 66 kDa is detected in different maize tissues indicating that the 66 kDa-NADP-ME is in fact a protein expressed in vivo. The recombinant NADP-ME assembles as a dimer, although the results obtained indicate that a higher molecular mass oligomeric state of the enzyme is found in maize roots in vivo. In this way, maize presents at least three NADP-ME isoforms: a 72 kDa constitutive form (previously characterized); the novel non-photosynthetic 66 kDa isoform characterized in this work (which is the product of the ZmChlMe2 gene and the likely precursor to the evolution of the photosynthetic C4 NADP-ME) and the 62 kDa isoform (implicated in C4 photosynthesis). The contribution of the present work anticipates further studies concerning the equilibrium between the oligomeric states of the NADP-ME isoforms and the evolution towards the C4 isoenzyme in maize.
ISSN:0167-4412
1573-5028
DOI:10.1007/s11103-004-0472-z