FERREDOXIN-NADP+ REDUCTASE FROM Escherichia coli CONTAINS TIGHTLY BOUND NADP+

LÓPEZ RIVERO, ARLETH; CECCARELLI, EDUARDO A.; CATALANO DUPUY, DANIELA L.

Ciudad Autónoma de Buenos Aires

Congreso; Reunión Anual de la SAIB 2013; 2013

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

FERREDOXIN-NADP+ REDUCTASE FROM Escherichia coli CONTAINS TIGHTLY BOUND NADP+ López-Rivero A, Ceccarelli EA, Catalano Dupuy DL. Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET-UNR. E-mail: lopezrivero@ibr-Conicet.gov.ar 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 plastidic-type 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.