Characterization of malate metabolism enzymes induced during soybean seed filling

COSTA, J.; BADIA, M. B.; PAVLOVIC, T.; ANDREO, C. S.; DRINCOVICH, M. F.; SAIGO, M.; GERRARD WHEELER, M. C.

Buenos Aires

Congreso; Reunión Conjunta de Sociedades de Biociencias; 2017

SAIC-SAIB-SAI-SAA-SAB-SAB-SAFE-SAFIS-SAH-SAP

Seeds are of great economic interest due to the value of their organic composition. The metabolic pathways leading to the deposition of triacylglycerols and proteins in seeds are complex in terms of the amount of enzymes involved, regulatory context and variability between species. Previous studies of our group indicated that NAD- and NADP-dependent malic enzymes (ME) participate in the provision of reducing power and citrate or acetyl-CoA, respectively, to the pathways of reserve biosynthesis during soybean maturation. In this context, the aim of this work was to analyze the biochemical and regulatory properties of the enzymes belonging to this family. For this, the different ME isoforms were obtained through cloning, heterologous expression in Escherichia coli and subsequent purification. Our results indicated that the only plastidic NADP-ME detected in seeds has a high affinity for its substrates malate and NADP. Furthermore, it is activated by glutamine, the main nitrogen compound that is imported to the seed to support the synthesis of reserves. On the other hand, the mitochondrial NAD-ME isoforms also showed an important positive regulation by metabolites present in the seed, being NAD-ME2.4 (the product of the most abundant transcript throughout the filling) the most regulated. The activation by fructose-1,6-bisphosphate and phosphoenolpyruvate, both produced during irreversible steps of glycolysis, indicates a coordination between this pathway and the malate metabolism. In turn, the activation of NAD-ME proteins by CoA and acetyl-CoA suggests their involvement in fatty acid biosynthesis. These findings provide new insights into intermediary metabolism in oilseeds and nominate ME as new biotechnological tools to be used in breeding programs.