Mediated electrochemistry of nitrate reductase from Arabidopsis thaliana

Herein we report the mediated electrocatalytic voltammetry of the plant molybdoenzyme nitrate reductase (NR) from Arabidopsis thaliana using the established truncated molybdenum-heme fragment at a glassy carbon (GC) electrode. Methyl viologen (MV), benzyl viologen (BV), and anthraquinone-2-sulfonic acid (AQ) are employed as effective artificial electron transfer partners for NR, differing in redox potential over a range of about 220 mV and delivering different reductive driving forces to the enzyme. Nitrate is reduced at the Mo active site of NR, yielding the oxidized form of the enzyme, which is reactivated by the electro-reduced form of the mediator. Digital simulation was performed using a single set of enzyme dependent parameters for all catalytic voltammetry obtained under different sweep rates and various substrate or mediator concentrations. The kinetic constants from digital simulation provide new insight into the kinetics of the NR catalytic mechanism.