IAL   21557
INSTITUTO DE AGROBIOTECNOLOGIA DEL LITORAL
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Simultaneous Allosteric Activation of ADPglucose Pyrophosphorylase: A simplified kinetic model
Autor/es:
M.C. ESPER, M. ALEANZI, G. SIANO, A.A. IGLESIAS
Lugar:
Villa Carlos Paz, Córdoba, Argentina
Reunión:
Congreso; XLIII Reunión Anual de SAIB; 2008
Institución organizadora:
SAIB
Resumen:
EN-P10.SIMULTANEOUS ALLOSTERIC ACTIVATION OF ADPGLUCOSEPYROPHOSPHORYLASE: A SIMPLIFIEDKINETIC MODEL1 1 2 1 Esper MC , Aleanzi M , Siano G , Iglesias AA .1 2 Lab Enzimología Molecular, Lab Analít Gral, Fac Bioq y Cs Biol,UNL, S3000ZAA, Santa Fe. Arg. E-mail: mesper@fbcb.unl.edu.arAgrobacterium tumefaciens ADPGlc PPase (EC 2.7.7.27) isactivated by two metabolites: pyruvate and fructose 6-phosphate(F6P). Both compounds mainly increase V , although at different maxlevels for each. In this work, we studied the simultaneous effect ofpyruvate and F6P, and found a decrease in A corresponding to one 0.5activator in the presence of the second one, which may correlate witha mutual positive cooperative binding. Nevertheless, the effect onthe catalytic step is not mutually positive in cooperativity, since atsaturating concentrations of both activators, pyruvate leadsactivation even when it exerts a lower effect than F6P.We postulate asimple mechanism in which both activators bind to the free enzyme,to the complexes enzyme-susbtrate and enzyme-second activator.Using the MATLAB program, experimental data were fitted to thevelocity equation and kinetic parameters were evaluated. Calculatedsubstrate and activators apparent dissociation constants fromenzyme complexes with both activators bound, were lower thanthose from enzyme complexes with only one activator. Also, dataenvisage that at saturating levels of both activators the predominantactivated conformational state corresponds to that produced bypyruvate. These results preclude the assumption of a competitivebehaviour and suggest that the binding site is not exactly the samefor both activators.