Mechanism of aquacobalamin decomposition in aqueous aerobic solutions containing glucose oxidase and glucose

In this work, we showed that aquacobalamin (H2OCbl) undergoes decomposition in the presence of glucose oxidase and glucose under aerobic conditions at pH 6.3. This process is contributed by two reactions performed by glucose oxidase, i.e. (i) H2OCbl transformation to cob(II)alamin in the course of the reaction with reduced form of glucose oxidase, and (ii) hydrogen peroxide generation. Further reaction between cob(II)alamin and H2O2 results in macrocycle destruction. Although the reaction between H2OCbl and reduced glucose oxidase is slow, it is accelerated by several phenols and 1,4-benzoquinone. The most pronounced effect of 1,4-benzoquinone and hydroquinone can be explained by the formation of complexes with reduced glucose oxidase, which are more reactive toward H2OCbl than initial reduced glucose oxidase. 1,4-benzoquinone accelerates H2OCbl decomposition in glucose oxidase/glucose system as well.