Study of the Regulation of NADP-Malic Enzyme (Decarboxylating) and Influence of Stress on this Enzyme

4. Conclusions l. Non-photosynthetic cytosolic isoform of NADP-mďic ilZ-oe (oxaloacetate decarboxylating) (NADp-ME; EC r.l.l.4o) was isolated from tobacco (Nicoriana tabacun L.) leaves. Specific aďiviý of the obtained enz5me preparation was 0.95pmol.miď|.mg l, relďive molecular mass of one subr'nit of tetramer approximatety 67000' pI 5'5 and pH optimum 7.r - 7.4. Kinetic constants of this isoform were determined for L-ma|ate and NADP+ in the presence of various cofactors Mď*, Mo*,co2', Ni2*, similarly the dependencies ofreaction Íates on the ooncentration ofdivalent metal ions were observed- The dependence of reaction rate on Mn2+ concentration wassigmoidal with strong positive cooperativiý and high value of Hill coefficient 7.5. -2r - J. 4. Summarv ofPh.D.Thesis 2. The kinetic meohanism of two-substate reaďion catalyzed by NADP.ME ůomtobacco leaves was determined as ordered sequmtial. The regulation of the NADP-ME purified ůomtobacco leaves occurs predominant|y in the prsence of macmergic compounds (GTP, ATP and ADP), sligbtly by metabolites of glymlysis. Biotic stress caused by potato yirus f G1;Y) (not only strain PWNN but also PWo) increased NADP.ME activiý in N. tabacum L. |eaves, stems and roots during the infeďion. Milder PVYo caused tower increase of NADP-ME aďivity than necrotic isolate of PVYNN...