On the Role of Peach Aldose-6-phosphate Reductase Against Oxidative Stress

HARTMAN, MD; FIGUEROA, CM; ARIAS, DG; IGLESIAS, AA

Mar del Plata

Congreso; LI Reunión Anual de SAIB; 2015

SAIB

Glucitol (Gol) metabolism in plants has been studied in the last 20 years, though the mechanisms regulating the enzymes involved are not deeply understood. Gol is a compatible solute of relevance to protect cells exposed to osmotic stress. Gol is produced in leaves by two succeeding steps: i) NADPH dependent reduction of glucose-6-phosphate into glucitol-6-phosphate by aldose 6-phosphate reductase (Ald-6PRase), and ii) the subsequent dephosphorylation of Gol-6P. Here we report that beyond the osmoprotectant role of Gol its metabolism would be regulated in response to oxidative stress. Under stressful conditions, susceptible proteins are oxidized, with consequent detrimental changes. NADPH is the main reducing power source to sustain antioxidant systems involved in maintaining cell functionality. Ald-6PRase activity is diminished by oxidants compounds and the inactivation is not restored by reducing agents. Furthermore, oxidants produce destabilization inducing protein aggregation. Experiments performed with labelled glutathione showed that Ald-6PRase is glutathionylated, a modification that protects the enzyme against oxidative aggregation. Oxidative inactivation of Ald-6PRase would decrease the carbon flux through the polyol pathway, thus preserving NADPH to feed antioxidant systems. The process would be modulated by glutathione to balance oxidative and osmotic stresses.