\b[Urate] denotes an <anion> obtained by removing one or more <protons> from <uric acid>; the charge state should be specified when needed. The commonly discussed monoanion has formula $\mathrm{C_5H_3N_4O_3^-}$, whereas neutral <uric acid> has one additional hydrogen. A urate salt includes charge-balancing <cations> as well as the urate ion.<Urate anions in ChEBI>[CHEBI:46818, definition and salt relation; CHEBI:30848, formula and charge]{ref}

Writing neutral <uric acid> as $\mathrm{H_2U}$ and its monoanion as $\mathrm{HU^-}$ gives the acid–base equilibrium
$$
\mathrm{H_2U\rightleftharpoons H^++HU^-}.
$$
This changes <protonation> and charge without changing the carbon, nitrogen or oxygen framework. In a simplified mixture containing only these two forms, a concentration ratio $[\mathrm{HU^-}]/[\mathrm{H_2U}]=4$ means that four fifths of their combined amount is monoanion. A total of1millimole would then comprise0.8millimole monoanion and0.2millimole neutral acid; the ratio alone does not specify the total amount.

The formation of urate in <purine> metabolism is a separate chemical transformation: <xanthine dehydrogenase> oxidizes <xanthine> toward the uric-acid/urate product family. That reaction changes the oxidation state and oxygen content, whereas the equilibrium above describes loss or gain of a <proton> after a particular framework has been specified.<Xanthine dehydrogenase in IUBMB Enzyme Nomenclature>[EC1.17.1.4, Reaction and Comments]{ref}


 Urate (source code)