| Abstract
| - In this study we focused on the effect of a pretreatment with high (20%) CO2 levels on malic acidmetabolism in cherimoya (Annona cherimola Mill) fruit stored at chilling temperature. We analyzedthe activity of phosphoenolpyruvate carboxylase (PEPC), malate dehydrogenase (MDH), and theNADP−malic enzyme (NADP−ME), involved in the carboxylation/decarboxylation of malate. Ourresults show that CO2 treatment, which improves tolerance to prolonged storage at chilling temperature,was closely linked to considerably greater NADP−ME activity. These results, combined with lowerPEPC activity, may explain the significantly lower amount of malic acid and titratable acidity quantifiedin CO2-treated fruit. Moreover, the high cytoplasmic MDH enzyme activity and the strong stimulationof NADP−ME activity exhibited by CO2-treated fruit could be contributing factors in the maintenanceof fruit energy metabolism, pH stability, and the promotion of synthesis of defense compounds thatprevent or repair damage caused by chilling temperature. Keywords: Cherimoya; chilling temperature; titratable acidity; malate; carbon dioxide; phosphoenolpyruvate carboxylase; malate dehydrogenase; malic enzyme
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