Resonance Raman Spectra of Manganese-Porphyrins on Ion-Exchange Resins Exhibiting Uricase-Like Catalytic Activity

Abstract

Ion-exchange resins modified with some manganese(III)-porphyrins (Mn³⁺-P_r) show a uricase-like catalytic activity, which is applicable to the determination of uric acid. The resonance Raman spectra of Mn³⁺-P_r indicate that Mn³⁺- porphyrins on modified resins are reduced to Mn²⁺-porphyrins with oxidizing uric acid; Mn²⁺-porphyrins then return to Mn³⁺-porphyrins by oxidation with O₂ in the reaction system. It was concluded on the basis of these results that the modified resins show an uricase-like activity by repeating this redox cycle of manganese-porphyrins on the modified resins. Mn³⁺-P_r exhibited no oxidative catalytic activity for 7-methylated derivatives of uric acid, indicating that the nitrogen atom at the 7-position of uric acid plays an important role in the activity of Mn³⁺-P_r.