Electrochemical and peroxidase catalysed oxidation of 9-β-D-ribofuranosyluric acid 5′-monophosphate

Abstract

The electrochemical oxidation of 9-β-D-ribofuranosyluric acid 5′-monophosphate (UA-9R-5′-P) in aqueous solution has been studied in the pH range 2.10–10.0. The evidence strongly indicates that UA-9R-5′-P is oxidized in a 2e^–, 2H⁺ reaction to give an unstable diimine which subsequently decomposes. A UV absorbing intermediate is observed during electrooxidation which decays in a pseudo first-order reaction to give alloxan, urea and ribosyl phosphate at pH 3.0. Controlled potential electrolysis results in the transfer of 2.0 ± 0.2 electrons per molecule and three major products are obtained at pH 7.0; allantoin, 5-hydroxyhydantoin-5-carboxamide and D-ribose. Tentative reaction schemes are proposed to explain the formation of these products.

Oxidation of UA-9R-5′-P in the presence of peroxidase and H₂O₂ also generates an intermediate which has spectral and kinetic properties identical to those of the intermediate generated electrochemically. Thus, it is believed that electrochemical and enzymic oxidation of UA-9R-5′-P proceed by identical reaction mechanisms.