CEFOBI   05405
CENTRO DE ESTUDIOS FOTOSINTETICOS Y BIOQUIMICOS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Estudio de la relación estructura-función de la enzima málica de Escherichia coli: modificación de sus propiedades para aplicaciones biotecnológicas
Autor/es:
BOLOGNA F,; CARLOS SANTIAGO ANDREO; DRINCOVICH MF,
Lugar:
Buenos Aires
Reunión:
Congreso; VII Feria Congreso Latinoamericano de Biotecnología y III Congreso Argentino de Biotecnología.; 2006
Institución organizadora:
Foro Biotecnología
Resumen:
Malic enzyme (ME) catalyses the oxidative decarboxylation of malate to yield pyruvate, CO2 and NAD(P)H. Two isoforms of ME have been identified by sequence homology in E. coli: sfcA (or maeA) and maeB (or ypfF). After cloning in an expression vector and over-expressing both ME isoforms, the purified recombinant enzymes were characterized, presenting several distinct kinetic and structural properties. In the present work, secondary reactions and metabolic regulation of the recombinant ME were analyzed. The pyruvate carboxylase activity was tested and the Km for pyruvate was obtained for both enzymes. These values indicate that this activity may not be important in vivo. In addition, the partition for oxaloacetate and the reduction of pyruvate were also analyzed. Interestingly, both enzymes were modulated by several metabolites. In the case of MaeB, it was strongly activated by glucose-6P and aspartate, although there was a minor activation due to oxaloacetate and glutamate. acetil-CoA, fumarate and fructose-6P inhibited this enzyme. SfcA was strongly inhibited by oxaloacetate and activated by aspartate. These results indicate that both enzymes may fulfill different metabolic roles in vivo and that their activity is highly regulated by different key metabolic compounds