xanthine-8-carboxylate + H(+) => pteridine-2,4,6,7-tetrol
xanthine-8-carboxylate + h(+) => pteridine-2,4,6,7-tetrol
xanthine-8-carboxylate + H(+) => pteridine-2,4,6,7-tetrol
xanthine-8-carboxylate + h(+) => pteridine-2,4,6,7-tetrol