IAL   21557
INSTITUTO DE AGROBIOTECNOLOGIA DEL LITORAL
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
The Ancestral Activation Promiscuity of ADP-glucose Pyrophosphorylases from Oxygenic Photosynthetic Organisms
Autor/es:
C.M. FIGUEROA; M.L. KUHN; A.A. IGLESIAS; M.A. BALLICORA
Lugar:
Minneapolis
Reunión:
Congreso; Annual Meeting of the American Society of Plant Biologists of Plant Physiologists; 2011
Institución organizadora:
American Society of Plant Biologists
Resumen:
ADP-glucose pyrophosphorylase (ADP-Glc PPase) catalyzes the first committed step in thesynthesis of bacterial glycogen and starch in plants. In oxygenic photosynthetic organisms,it is mainly activated by 3-phosphoglycerate (3-PGA). Here, we analyzed the activationpromiscuity of ADP-Glc PPase from Anabaena (cyanobacteria), and the subunits from theunicellular algae Ostreococcus tauri (OtaS/OtaL), and potato tuber (StuS/StuL) bycomparing the Activation/A0.5 specificity constant for 3-PGA, fructose-1,6-bisphosphate(FBP), fructose-6-phosphate, and glucose-6-phosphate. The 3-PGA specificity constants forthe Anabaena, OtaS/OtaL and StuS/StuL enzymes (73.3, 60.7, and 1259 mM-1) were higherthan for other activators (18-, 9.4-, and 34-fold higher than the second activator, respectively). This apparent omnipresent promiscuity in divergent organisms suggests a very distant common ancestry. Interestingly, the OtaS homotetramer was even morepromiscuous with an FBP specificity constant similar to the one for 3-PGA. To explore therole of OtaS and OtaL in determining the specificity of the heterotetramer, we knocked thecatalytic activity of each subunit by mutagenesis. Both constructs OtaSD149A/OtaL andOtaS/OtaLD171A had higher specificity constants for 3-PGA than for FBP (2527 and 153 mM-1 compared with 0.61 and 3.9 mM-1, respectively). After gene duplication, OtaS seemed to have lost specificity for 3-PGA compared to FBP. This was physiologically possible because co-expression of both subunits restored the specificity for 3-PGA of the resulting heterotetrameric wild type enzyme. This ancestral promiscuity could constitute an efficient evolutionary mechanism to accommodate different metabolic needs and ADP-Glc PPase regulation.