TY  - JOUR
A1  - Kalimuthu, Palraj
A1  - Leimkühler, Silke
A1  - Bernhardt, Paul V.
T1  - Xanthine dehydrogenase electrocatalysis autocatalysis and novel activity
JF  - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry
N2  - The enzyme xanthine dehydrogenase (XDH) from the purple photosynthetic bacterium Rhodobacter capsulatus catalyzes the oxidation of hypoxanthine to xanthine and xanthine to uric acid as part of purine metabolism. The native electron acceptor is NAD(+) but herein we show that uric acid in its 2-electron oxidized form is able to act as an artificial electron acceptor from XDH in an electrochemically driven catalytic system. Hypoxanthine oxidation is also observed with the novel production of uric acid in a series of two consecutive 2-electron oxidation reactions via xanthine. XDH exhibits native activity in terms of its pH optimum and inhibition by allopurinol.
Y1  - 2011
U6  - https://doi.org/10.1021/jp111809f
SN  - 1520-6106
VL  - 115
IS  - 11
SP  - 2655
EP  - 2662
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Kalimuthu, Palraj
A1  - Leimkühler, Silke
A1  - Bernhardt, Paul V.
T1  - Catalytic electrochemistry of xanthine dehydrogenase
JF  - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry
N2  - We report the mediated electrocatalytic voltammetry of the molybdoenzyme xanthine dehydrogenase (XDH) from Rhodobacter capsulatus at a thiol-modified Au electrode. The 2-electron acceptor N-methylphenazinium methanesulfonate (phenazine methosulfate, PMS) is an effective artificial electron transfer partner for XDH instead of its native electron acceptor NAD(+). XDH catalyzes the oxidative hydroxylation of hypoxanthine to xanthine and xanthine to uric acid. Cyclic voltammetry was used to generate the active (oxidized) form of the mediator. Simulation of the catalytic voltammetry across a broad range of substrate and PMS concentrations at different sweep rates was achieved with the program DigiSim to yield a set of consistent rate and equilibrium constants that describe the catalytic system. This provides the first example of the mediated electrochemistry of a xanthine dehydrogenase (or oxidase) that is uncomplicated by interference from product oxidation. A remarkable two-step, sequential oxidation of hypoxanthine to uric acid via xanthine by XDH is observed.
Y1  - 2012
U6  - https://doi.org/10.1021/jp307374z
SN  - 1520-6106
VL  - 116
IS  - 38
SP  - 11600
EP  - 11607
PB  - American Chemical Society
CY  - Washington
ER  -