Characterization of NADP-malic enzyme from Nicotiana tabacum: cloning and biological role analysis

MÜLLER, GABRIELA LETICIA; ANDREO, CARLOS SANTIAGO; DRINCOVICH, MARÍA FABIANA; LARA, MARÍA VALERIA

Mar del Plata

Congreso; XLIII Runión anual de SAIB; 2007

NADP-Malic Enzyme (NADP-ME) catalyzes the oxidativedecarboxylation of L-malate producing pyruvate, CO2 andNADPH. In plants the enzyme is related to carbon fixation in C4 andCrassulacean Acid Metabolism (CAM) plants. In C3, C4 and CAMplants non-photosynthetic isoforms have also been described. Theaim of this study was to characterize the different isoforms ofNADP-ME from . Three different enzymes wereidentified. All of them are expressed in vegetative as well as inreproductive tissues but with different expression patterns. Root isthe tissue that displays the highest activity. Only one isoform istargeted to plastids (DQ923119) while the others are cytosolic(DQ923118, EH663836). Real time RT-PCR studies and activityassays showed that NADP-MEs from tobacco respond to differentbiotic and abiotic stress stimulus. Enzymes encoded by DQ923118and DQ923119 were recombinant expressed in andtheir kinetic parameters and response to different effectors wereanalyzed. Studies carried out with crude extracts and with therecombinant proteins indicated that the cytosolic and plastidicisoforms aggregate as tetramers of subunits of 65.4 and 63.3 kDa,respectively.Finally, the physiological role of each isoform is discussed in termsof the occurrence, kinetic properties and response to stress.