Wheat Cytosolic Glyceraldehyde-3-phosphate Dehydrogenases are Differentially Redox Regulated

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

Villa Carlos Paz, Córdoba, Argentina

Congreso; XLIII Reunión Anual de SAIB; 2008

SAIB

PL-P29.Wheat CYTOSOLIC GLYCERALDEHYDE-3-PHOSPHATEDEHYDROGENASES ARE DIFFERENTIALLY REDOXREGULATEDPiattoni CV, Guerrero SA, Iglesias AA.Laboratorio de Enzimología Molecular y Laboratorio deBioquímica Microbiana, FBCB, UNL, Santa Fe. E-mail:piattoni@fbcb.unl.edu.arIn plants, glycolysis is a complex network where specific steps arecritical for regulation. Thus, oxidation of Ga3P to 3P-glycerate inthe cytosol of plant cells is achieved by two different pathways.One involves phosphorylating Ga3P dehydrogenase (Ga3PDHase,EC 1.2.1.12) and 3P-glycerate kinase, where triose-P derives in thesynthesis of ATP and NADH. The other route, catalyzed by the nonphosphorylatingGa3P dehydrogenase (npGa3PDHase; EC1.2.1.9), leads triose-P to the synthesis of NADPH. An ongoing andchallenging problem is to elucidate the regulation of thesealternative reactions of glycolysis, whereby extracellular stimulicoordinate the intermediary metabolism. We characterized redoxmodifications occurring on cytosolic Ga3PDHase andnpGa3PDHase from wheat. Both enzymes were inactivated bydifferent thiol oxidants as diamide, hydrogen peroxide, sodiumnitroprusside, oxidized glutathione and S-nitrosoglutathione. Theloss of activity was effectively reversed after incubation withvarious reducing agents, suggesting that the process could functionphysiologically. Interestingly, Ga3PDHase was markedly moresensitive to oxidants than npGa3PDHase. We conclude that underoxidative conditions, the oxidation of triose-P is preferably utilizedfor NADPH generation, being a key metabolic point to regulatecarbon, energy and redox equivalents partitioning in plant cellcytosol.