| Title |
Studies of reduction mechanisms of quinones and nitroaromatic compounds by flavoenzymes dehydrogenases-transhydrogenases / |
| Translation of Title |
Chinonų ir nitroaromatinių junginių redukcijos flavininėmis dehidrogenazėmis-transhidrogenazėmis mechanizmų tyrimai. |
| Authors |
Valiauga, Benjaminas |
| Full Text |
|
| Pages |
168 |
| Keywords [eng] |
flavoenzymes ; thioredoxin reductase ; nitroreductase ; quinones ; nitroaromatic compounds. |
| Abstract [eng] |
In this work two flavoenzymes dehydrogenases-transhydrogenases are investigated - E. coli nitroreductase A (NfsA) and T. maritima thioredoxin reductase (TmTR). Recently, nitroreductases have acquired more interest concerning problems with biodegaration of nitroaromatic compounds and gene-directed enzyme prodrug therapy. TmTR-catalyzed reactions are also relevant due to interest of application of hyperthermophylic organisms in the synthesis of fuel and industrial chemicals. It was determined that two-electron reduction of quinones and nitroaromatic compounds by NfsA follows “ping-pong” kinetics and the rate-limiting step is the oxidative half-reaction. The experimental data are most consistent with a single-step (H-) hydride transfer mechanism in the reduction of quinones by NfsA. The obtained data argue for the major role of direct reduction by NADPH in the reduction of intermediate nitroso compound. The determined E07 value of FMN cofactor of NfsA (-0.215 V) is close to that of E. cloacae nitroreductase (-0.190 V). TmTR catalyzes mixed 1e- and 2e- reduction of quinones and nitroaromatic compounds. Reaction follows „ping-pong“ kinetics with a rate-limiting oxidative half-reaction. Accumulation of FAD semiquinone (FADH●) during the TmTR-catalyzed reduction of quinones indicates that the oxidation of FADH● may be a rate-limiting step in this reaction. The redox potential of FAD of TmTR, -0.230 V, is close to redox potentials of other low molecular mass thioredoxin reductases. |
| Dissertation Institution |
Vilniaus universitetas. |
| Type |
Doctoral thesis |
| Language |
English |
| Publication date |
2020 |
