The Standard Potential of Glucose Oxidase

Abstract

Glucose oxidase was titrated with Cr(II) and with Ti(III) over a pH range from 5.0 to 6.0, and a temperature range of 25° to 40°C. The two inorganic reagents were used, rather than just one, to ensure that there was no specific interaction between the enzyme and the reagent. Simultaneously, it was shown that the stoichiometry of the enzyme‐inorganic reductant reaction was identical to that of the enzyme‐glucose reaction and that the reduction products were identical in each case. Thus, it is shown that the potentials found are truly those which apply in the enzymatic oxidation of glucose. Glucose could not be used as reductant in the potentiometric studies because neither the enzyme nor the glucose reacts at the electrode. The values of Eo‘ (median reduction potential at pH 7) are −0.061v at 40°C, −0.028v at 30°C, and −0.008v at 25°C.

Mediator-free amperometric glucose biosensor based on glucose oxidase entrapped in poly(vinyl alcohol) matrix

“…For both pairs a is almost 0.5 (a typical value) and n z 4, suggesting that both FAD moieties of the dimer GOx are involved in the process, each one employing 2e À in the redox process. [43][44][45] The k s values obtained from the intercepts (5.6 Â 10 À2 s À1 and 2.4 Â 10 À2 s À1 ) were revealed to be comparable with values obtained with similar systems based on GOx molecules adsorbed at the electrode surface. 46 Furthermore, an increase in pH (from 3 to 8) causes a negative shift in E p (I) and E p (II) slope of respectively À30 mV/pH for peak pair (I) and À36 mV/pH for peak pair (II) (see Fig.…”

Amperometric enzyme electrode for determination of glucose based on thin-layer spectroelectrochemistry of glucose oxidase

“…A better reproducibility and a better control of the electrode surface are necessary in order to make spectroelectrochemistry a quantitative tool adapted to the study of intramolecular electron transfer in oxido-reduction enzymes. Nevertheless the present study confirms the proximity of the standard potentials for the G00/GOs and GOs/GOr systems already observed in potentiometric titration experiments (9,(15)(16)(17) and brings another example of the Usefulness of spectroelectrochemistry in the elucidation of complex processes. Complete reoxidation of GO solutions is very slow in the potential range above, but for a 0.5 V applied potential, oxidation is finished in about 1 h. Electrolysis has also been done on GO solutions 0.250 mM in classic electrochemical cells, with platinum working electrode at the potential of -0.55 V. Complete reduction of solutions 1.5 cm3 in volume occurs in about 3 h when carried out under an argon atmosphere with evolution of the solution from yellow to colorless through a green intermediate.…”

Covalent Attachment of Osmium Complexes to Glucose Oxidase and the Application of the Resulting Modified Enzyme in an Enzyme Switch Responsive to Glucose

“…Modified Electrodes. It is known that GOx adsorbs on platinum, 25 gold, 26 and graphite. 27 We have therefore investigated the possible adsorption of the modified GOx at glassy carbon and platinum electrodes.…”