On the Regulation of Triose-phosphate Metabolism by Protein Phosphorylation

C.V. PIATTONI; S.A. GUERRERO; A.A. IGLESIAS

Puerto Madryn

Congreso; XLVI Reunión Anual de SAIB; 2010

SAIB

ON THE REGULATION OF TRIOSE-PHOSPHATE METABOLISM BY PROTEIN PHOSPHORYLATION Piattoni CV, Guerrero SA, Iglesias AA Instituto de Agrobiotecnología del Litoral (IAL), UNL-CONICET, Santa Fe, Argentina. E-mail: Posttranslational modifications, as protein phosphorylation, regulate different processes in plants. In this work we analyzed phosphorylation of two plant cytosolic Ga3P dehydrogenases: the phosphorylating (Ga3PDHase, EC 1.2.1.12), and the nonphosphorylating (np-Ga3PDHase, EC 1.2.1.9) enzymes; which respectively derive triose-P to the synthesis of ATP and NADH or NADPH. We found that, in wheat endosperm, a protein kinase from the SnRK1 family is involved in modification of both Ga3PDHases. Phosphorylation occurs on residues Ser404 (np-Ga3PDHase) and Ser205 (Ga3PDHase), which localize in respective conserved domains that were described as preferred sites for SnRK1 phosphorylation. We purified and characterized the wheat 2+ 2+ endosperm SnRK1 kinase. The enzyme required Mg or Mn (but 2+ not Ca ) for activity and it was allosterically inhibited by nearly physiological concentrations of Rib5P and to a lesser extent by Fru1,6bisP and 3PGA. Glc6P (the main effector of spinach leaf SnRK) produced little or no effect. MALDI-TOF analysis evidenced that sucrose synthase copurified with SnRK1, the former also being a target of the kinase action. We hypothesize that phosphorylation of both Ga3PDHases by SnRK1 would occur within a mechanism (specific of heterotrophic tissues) that coordinates carbon metabolism during the stage of reserve carbohydrates accumulation in developing wheat seeds.