The extremophilic Andean isolate Acinetobacter sp. Ver3 expresses two ferredoxin-NADP+ reductase isoforms with different catalytic properties

Abstract

Ferredoxin/flavodoxin-NADPH reductases (FPRs) catalyze the reversible electron transfer between NADPH and ferredoxin/flavodoxin. The Acinetobacter sp. Ver3 isolated from high-altitude Andean lakes contains two isoenzymes, FPR1_ver3 and FPR2_ver3. Absorption spectra of these FPRs revealed typical features of flavoproteins, consistent with the use of FAD as a prosthetic group. Spectral differences indicate distinct electronic arrangements for the flavin in each enzyme. Steady-state kinetic measurements show that the enzymes display catalytic efficiencies in the order of 1-6 μm^-1·s^-1, although FPR1_ver3 exhibited higher k_cat values compared to FPR2_ver3. When flavodoxin_ver3 was used as a substrate, both reductases exhibited dissimilar behavior. Moreover, only FPR1_ver3 is induced by oxidative stimuli, indicating that the polyextremophile Ver3 has evolved diverse strategies to cope with oxidative environments.

Keywords: Acinetobacter sp.; Andean wetlands; Ferredoxin/flavodoxin‐NADP (H) reductases; extremophile isolates; oxidative stress.