Regulation of Wheat Cytosolic Glyceraldehyde-3-phosphate Dehydrogenase by Redox Mechasnisms

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

Minneapolis

Congreso; Annual Meeting of the American Society of Plant Biologists of Plant Physiologists; 2011

American Society of Plant Biologists

Plant glycolysis is a particular complex network where specific steps seem critical forregulation. The conversion of glyceraldehyde-3-phosphate (Ga3P) into 3-phosphoglycerate(3-PGA) is one key point of this metabolic pathway catalyzed by two different enzymes inplant cells cytosol. Regulation of this critical step in determining triose-P fate is far to besatisfactorily understood. We studied posttranslational modifications operating on the twoplant cytosolic Ga3P dehydrogenases: the phosphorylating enzyme (p-Ga3PDHase, EC1.2.1.12) [that together with 3-PGA kinase derives triose-P to the synthesis of ATP andNADH], and the non-phosphorylating enzyme (np-Ga3PDHase; EC 1.2.1.9) [that leadstriose-P to produce NADPH]. Both enzymes were found targets of redox modification byreactive oxygen and nitrogen species (ROS and RNS, respectively), being p-Ga3PDHasemarkedly more sensitive to thiol oxidants than np-Ga3PDHase. Thus, p-Ga3PDHase wasoxidized by H2O2 with a k" of 119 M-1 s-1, which is 63-fold higher than that obtained fornp-Ga3PDHase oxidation. Loss of activity of both enzymes was deferentially but effectivelyreversed by reduced thioredoxin-h (TRX-h), suggesting that the process could functionphysiologically. Results support a rerouting of cytosolic triose-P toward synthesis of NADPH instead of ATP under oxidative cell conditions, which would favor antioxidant systems coping with oxidative stress. Furthermore, TRX-h would positively feedback NADPH production via np-Ga3PDHase by maintaining the enzyme at a reduced (more active) state.