Copper-adenine catalyst for O2 production from H2O2

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 O-2 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 O-2, production. As for C-40 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 C-40 catalase and that the molar activity for O-2 production is 200-fold weaker for Cu(adenine)(2) than for the enzyme. In the 10(-6)-10(-3) RI 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 O-2 production. (C) 1999 Academic Press.