Identification of domains involved in tetramerization and malate inhibition of maize C4-NADP malic enzyme

ENRIQUE DETARSIO; CLARISA ALVAREZ; MARIANA SAIGO; CARLOS ANDREO; MARÍA FABIANA DRINCOVICH

JOURNAL OF BIOLOGICAL CHEMISTRY

The American Society for Biochemistry and Molecular Biology

Lugar: Rockville; Año: 2007 vol. 282 p. 6053 - 6060

0021-9258

C4 photosynthetic NADP-malic enzyme (ME) has evolvedfrom non-C4 isoforms and gained unique kinetic and structuralproperties during this process. To identify the domains responsiblefor the structural and kinetic differences between maize C4and non-C4-NADP-ME several chimeras between these isoformswere constructed and analyzed. By using this approach,we found that the region flanked by amino acid residues 102 and247 is critical for the tetrameric state of C4-NADP-ME. In thisway, the oligomerization strategy of these NADP-ME isoformsdiffers markedly from the one that present non-plantNADP-MEwith known crystal structures. On the other hand, the region fromresidue 248 to the C-terminal end of the C4 isoform is involved inthe inhibition by high malate concentrations atpH7.0. The inhibitionpattern of the C4-NADP-ME and some of the chimeras suggestedan allosteric site responsible for such behavior. This pH-dependentinhibition could be important for regulation of the C4isoform in vivo, with the enzyme presenting maximum activitywhile photosynthesis is in progress.