Copper–Adenine Catalyst for O2 Production from H2O2

Abstract

In solutions of CuCl2 and adenine copper can be bound to adenine. Two Cu(adenine)2 complexes [Cu(C5H5N5)2]2+/Cu(C5H4N5)2] are in equilibrium with free adenine. Copper–adenine complexes present a catalatic activity (e.g., H2O2 disproportionation into O2 and water) but depending on complex concentration H2O2 also strongly oxidizes the adenine within the complexes. Raman spectroscopy quantifies copper–adenine complex formation and H2O2 consumption; polarography quantifies O2 production. As for C40 catalase, optimal catalatic capacities depend on physiological conditions, such as pH and temperature. The comparative analysis of kinetic parameters shows that the affinity for H2O2 of Cu(adenine)2 is 37-fold lower than that of C40 catalase and that the molar activity for O2 production is 200-fold weaker for Cu(adenine)2 than for the enzyme. In the 10−6–10−3 M range, the strong decrease of activity with raising complex concentration is explained by aggregation or stacking, which protects Cu(adenine)2 entities from H2O2 oxidation, but also decreases O2 production.