CONICET | Buscador de Institutos y Recursos Humanos

Ferredoxin-NADP+ reductases (FNR) are flavoenzymes involvedin biologically relevant processes. FNR catalyzes the reversibleelectron transfer between NADP(H) and ferredoxin or flavodoxin.The reaction involves a hydride exchange with the pyridine nucleotideand then an electron transfer to or from the other substrate.We have previously identified that Escherichia coli FNR is purifiedwith the substrate/product NADP+ tightly bound. The nucleotidebinding produces an inhibition of the enzyme activity which is lostwhen NADP+ is released. Our findings suggest that this inhibitionmay have a regulatory function on this bacterial FNR and would implicatea different catalytic mechanism than the one reported for theplastidic enzymes. E. coli FNR belongs to one of the three planttypeFNR groups in which these enzymes can be classified. Thesegroups have well-identified structural differences. One of the mostrelevant is located in the carboxyl terminus of FNR, where NADP+binding and catalysis occur. We have comparatively studied the catalyticproperties of FNR from different pathogenic bacteria: E. coli,Pectobacterium carotovorum, Brucella abortus and Leptospira interrogans,in order to determine if the phenomenon observed in E.coli reductase is a unique process of bacterial FNR. We found thatall the aforementioned reductases, except L. interrogans FNR, containNADP+ bound. Moreover, kinetic analyses of these enzymes allowedestablishing a direct correlation between the ability of high-affinitybinding of NADP+ and a decrease of their catalytic efficiences.It is important to note that L. interrogans possesses a plastidic FNR.We propose that this regulation would be an important aspect of thefunctionality of the enzymes and, therefore, in the regulation of redoxhomeostasis in bacteria. From these results, we propose usingthis high-affinity binding as a differential target for the inactivation ofmetabolic pathways in which FNR participate in pathogenic bacteria.

enviar mensaje