Ferredoxin-NADP+ reductase from Escherichia coli contains thigly bound NADP+

LOPEZ-RIVERO, A; CECCARELLI, E. A.; CATALANO DUPUY, D. L.

Buenos Aires

Congreso; XLIX Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2013

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

The Ferredoxin-NADP+ reductases (FNRs) are flavoenzymes that catalyze the reversible electron transfer between NADP(H) and ferredoxin or flavodoxin. Escherichia coli contains a bacterial-type FNR (EcFPR) involved in different biosynthetic pathways where reactions favor the reduction of ferredoxin or flavodoxin from NADPH in order to supply redox equivalents to diverse metabolisms. The bacterial-type FNRs are less active enzymes than the plastidictype reductases. The difference found in the catalytic efficiency is influenced by some structural features such as the conformation of the prosthetic group, the mobility and the structure of the C-terminal region, among others. The NADP+ binding mode may also condition the enzyme activity. We determined that purified EcFPR contains one mol of bound NADP+ per mol of enzyme. EcFPR free of NADP+ was obtained and then, the effect of the NADP+ binding on the enzyme activity analyzed. We observed a marked decrease in the KM value for the NADPH for EcFPR free of NADP+ suggesting an inhibition of the enzyme by product. EcFPR plays a role in NADPH/NADP+ homeostasis. Thus, this phenomenon could be related to a regulation mechanism of physiological relevance. Additionally, we studied the effect of different NADP+ analogues on the EcFPR diaphorase activity. We observed enzyme activation in the presence of these compounds.