| Abstract [eng] |
Flavin-containing dehydrogenases – electrontransferases are capable of transforming between two- and one- electron transfer in redox reactions with various electron acceptors via a ping-pong mechanism owing to the chemical activity conferred to the flavin by the isoalloxazine ring. Some of these electron acceptors, namely quinones, nitroaromatics and aromatic N-oxides, can be considered prooxidant xenobiotics, i.e., substances that can be found in a given organism yet not naturally produced by it. These xenobiotics can be reduced in a single-electron way upon catalysis by the three representative flavoenzymes that are presented in this work – ferredoxin:NADP + oxidoreductases from Plasmodium falciparum (PfFNR) and Rhodopseudomonas palustris (RpFNR) and rat neuronal NO synthase (nNOS). By combining steady- and presteady-state kinetics methods, comprehensive mechanistic studies on the aforementioned enzymes’-catalyzed reduction of xenobiotics were performed with the results in line with those obtained for homologous enzymes and reported earlier. Moreover, the photoreduction studies of RpFNR enabled a potentiometric characterization of this novel thioredoxin reductase-like FNR. Finally, it was shown that dehydrogenases – electrontransferases can be employed for the approximate determination of single-electron reduction potentials of nitroaromatics and aromatic N-oxides and the calculated electron transfer distances in these enzymes are in line with the outer sphere electron transfer model. |
