Isolation of Lecanoric Acid, an Inhibitor of Histidine Decarboxylase From a Fungus

A method of determining histidine decarboxylase activity was established. Inthis method, 14C-histamine was separated from 14C-histidine by Amberlite CG-resincolumn in the ammonium form. Lecanoric acid was obtained by screening histidine-decarboxylaseinhibitors produced by microorganisms. It is the first isolation of thiscompound from fungi. The inhibition by lecanoric acid was competitive with histidineand noncompetitive with pyridoxal phosphate. Lecanoric acid did not inhibitaromatic amino acid decarboxylase. Though lecanoric acid was hydrolyzed easilyboth in vivo and in vitro, its structure yielded an information useful in developinghistidine decarboxylase inhibitors of a new structural type.