The mechanism of the action of uricase

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Abstract
By using water and O2 labelled with O18 it was shown that the O atoms of the H2O2 formed in the oxidation of uric acid by uricase (from pig liver) are derived from O2. It was concluded that uricase catalyzes the transfer of 2 electrons from a urate ion to O. Uric acid labelled with Cl4 in the 6 position was synthesized. It was shown that the CO2 formed in the enzymic oxidation is derived from the C14. On the basis of the results reported here and the work of others a mechanism of enzymic oxidation of uric acid is proposed which assumes that the enzyme acts on the anion transforming it into a carbonium ion with loss of 2 electrons. The further changes which are probably non-enzymic consist mainly of an electrophilic rearrangement characteristic of carbonium ion structures. The possible role of carbonium ions as intermediates in biological oxidations and coupled phosphorylations is discussed.
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