nzymic conversion of 3-hydroxyanthranilic acid into cinnabarinic acid. Partial purification and properties of ra-liver cinnabarinate synthase.

Rat-liver cinnabarinate synthase (3-hydroxyanthranilic acid-oxygen oxido-reductase) was partially purified. Stoicheiometric studies indicated the consumption of 3 atoms of oxygen/molecule of cinnabarinic acid formed. There was an initial lag in enzyme activity. The reaction had an optimum pH about 7.2 and an optimum temperature of 37 degrees . The enzyme was highly specific for 3-hydroxyanthranilic acid. The system showed an absolute requirement for Mn(2+) ions. Several bivalent metal ions and metal-chelating agents inhibited the reaction. Thiol inhibitors had no effect on enzyme activity, but reducing agents such as ascorbic acid were potent inhibitors. There was no requirement for any cofactor other than Mn(2+) ions. The probable significance of the reaction in mammals is discussed.