Anthranilic acid hydroxylase from Tecoma stans

Abstract

A hydroxylase catalysing the conversion of anthranilic acid to 3-hydroxy-anthranilic acid has been isolated from the leaves of Tecoma stans. The enzyme was purified by fractional precipitation with acetone and adsorption on DEAE-cellulose to give about 84-fold increase in specific activity. The optimum ρ H for the reaction was 5.0. Among the compounds tested, only anthranilic acid was effective as substrate. The enzyme was inhibited by concentrations of anthranilic acid above 1 mM. Metal-chelating agents and sulfhydryl compounds produced marked inhibition. The enzyme was activated by Fe³⁺ and the inhibition with α -α ′-dipyridyl was specifically reversed by Fe³⁺. The enzyme showed an absolute requirement for tetrahydrofolic acid and reduced nicotinamide coenzymes for activity.