1. Redox Properties of Bacillus subtilis Ferredoxin:NADP + Oxidoreductase: Potentiometric Characteristics and Reactions with Pro-Oxidant Xenobiotics.
- Author
-
Lesanavičius M, Seo D, Maurutytė G, and Čėnas N
- Subjects
- Xenobiotics metabolism, Xenobiotics chemistry, Flavin-Adenine Dinucleotide metabolism, Flavin-Adenine Dinucleotide chemistry, Bacterial Proteins metabolism, Bacterial Proteins chemistry, Potentiometry, Oxidants chemistry, Quinones metabolism, Quinones chemistry, Electron Transport, Oxidation-Reduction, Ferredoxin-NADP Reductase metabolism, Ferredoxin-NADP Reductase chemistry, Bacillus subtilis enzymology
- Abstract
Bacillus subtilis ferredoxin:NADP
+ oxidoreductase ( Bs FNR) is a thioredoxin reductase-type FNR whose redox properties and reactivity with nonphysiological electron acceptors have been scarcely characterized. On the basis of redox reactions with 3-acetylpyridine adenine dinucleotide phosphate, the two-electron reduction midpoint potential of the flavin adenine dinucleotide (FAD) cofactor was estimated to be -0.240 V. Photoreduction using 5-deazaflavin mononucleotide (5-deazaFMN) as a photosensitizer revealed that the difference in the redox potentials between the first and second single-electron transfer steps was 0.024 V. We examined the mechanisms of the reduction of several different groups of non-physiological electron acceptors catalyzed by Bs FNR. The reactivity of quinones and aromatic N -oxides toward Bs FNR increased when increasing their single-electron reduction midpoint redox potentials. The reactivity of nitroaromatic compounds was lower due to their lower electron self-exchange rate, but it exhibited the same trend. A mixed single- and two-electron reduction reaction was characteristic of quinones, whereas reactions involving nitroaromatics proceeded exclusively via the one-electron reduction reaction. The oxidation of FADH• to FAD is the rate-limiting step during the oxidation of fully reduced FAD. The calculated electron transfer distances in the reaction with nitroaromatics were close to those of other FNRs including the plant-type enzymes, thus demonstrating their similar active site accessibility to low-molecular-weight oxidants despite the fundamental differences in their structures.- Published
- 2024
- Full Text
- View/download PDF