DOMAINS IMPLICATED IN TETRAMERIZATION AND MALATE INHIBITION OF MAIZE NADP-MALIC ENZYME

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

Rosario, Argentina

Congreso; XLII Reunión Anual de la SAIB; 2006

Sociedad Argentina de Investigaciones Bioquímicas y Biología Molecular

In plants, C4 photosynthetic NADP-malic enzyme (NADP-ME) has evolved from non-C4 isoforms during evolution and gained unique kinetic and structural properties. In order to identify the domains responsible for the structural and kinetic differences between maize C4- and non-C4 NADP-ME several reciprocal enzyme chimeras between these isoforms were constructed and analyzed. By this approach, a region between aminoacid residues 102 and 247 of the C4 NADP-ME was found to be implicated in the oligomerization state, being responsible for the tetrameric state of this isoform. In this way, the strategy for oligomerization of these NADP-ME isoforms differs markedly from the one that present non-plant NADP-ME crystallized to date. On the other hand, the region from residue 248 to the C terminal of the of the C4 isoform was implicated in the inhibition by high malate concentrations at pH 7.0. The inhibition pattern of the C4-NADP-ME and some of the chimeras suggested an allosteric site responsible for such inhibition. In this way, this inhibition may be important for the regulation of the C4 isoform in vivo; presenting maximum activity when photosynthesis is in progress.