Cinnabarinic acid formation in Malpighian tubules of the silkworm, Bombyx mori. Participation of catalase in cinnabarinic acid formation in the presence of manganese ion.

Cinnabarinic acid was formed from 3-hydroxyanthranilic acid during incubation with a soluble fraction from Malpighian tubules of the silkworm, Bombyx mori, in the presence of manganese ion. The enzyme having this activity was purified to homogeneity by ammonium sulfate fractionation, gel filtration and ion exchange chromatography. Enzyme activity was accompanied by parallel catalase activity at all steps of purification; the two activities could not be separated from each other. The purified protein was concluded to be catalase. Manganese was shown to be present in 0.1 mM concentration in Malpighian tubules of Bombyx mori. These findings suggest that in Malpighian tubules catalase participates in the formation of cinnabarinic acid. A possible mechanism for the formation of cinnabarinic acid from 3-hydroxyanthranilic acid by catalase in the presence of manganese ion is proposed.