Ferredoxin:NADP+ oxidoreductase as a target of Cd2+ inhibitory action – Biochemical studies
2010; Elsevier BV; Volume: 72; Issue: 1 Linguagem: Inglês
10.1016/j.phytochem.2010.10.010
ISSN1873-3700
AutoresJoanna Grzyb, Monika Bojko, Andrzej Waloszek, Kazimierz Strzałka,
Tópico(s)Plant Stress Responses and Tolerance
ResumoThe ferredoxin:NADP+ oxidoreductase (FNR) catalyses the ferredoxin-dependent reduction of NADP+ to NADPH in linear photosynthetic electron transport. The enzyme also transfers electrons from reduced ferredoxin (Fd) or NADPH to the cytochrome b6f complex in cyclic electron transport. In vitro, the enzyme catalyses the NADPH-dependent reduction of various substrates, including ferredoxin, the analogue of its redox centre – ferricyanide, and the analogue of quinones, which is dibromothymoquinone. This paper presents results on the cadmium-induced inhibition of FNR. The Ki value calculated for research condition was 1.72 mM. FNR molecule can bind a large number of cadmium ions, as shown by the application of cadmium-selective electrode, but just one ion remains bound after dialysis. The effect of cadmium binding is significant disturbance in the electron transfer process from flavin adenine dinucleotide (FAD) to dibromothymoqinone, but less interference with the reduction of ferricyanide. However, it caused a strong inhibition of Fd reduction, indicating that Cd-induced changes in the FNR structure disrupt Fd binding. Additionally, the protonation of the thiol groups is shown to be of great importance in the inhibition process. A mechanism for cadmium-caused inhibition is proposed and discussed with respect to the in vitro and in vivo situation.
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