Effect of cyclic AMP and acridine orange on the enzymatic reduction of usnic acid in the lichen Usnea aurantiaco-atra (Jacq.) Bory

Abstract

A fluorescence-detection HPLC procedure has been applied to identify and quantify acridine orange in lichen samples. The dye accumulates in thalli of the lichen Usnea aurantiaco-atra and, in part, it is recovered from protamine-precipitated nucleic acids extracted from the samples. A supply of exogenous cyclic AMP reverses the uptake of acridine orange by thallus samples and its binding to nucleic acids. The dye impedes neither the loss of endogenously-produced cyclic AMP by thallus samples nor inhibits the uptake of that exogenously supplied. However, part of the endogenously produced cyclic AMP is secreted to the incubation medium in which phosphodiesterase activity has never been detected. Since the synthesis of D-usnic acid: NAD⁺(H) oxido-reductase is impeded by acridine orange, oxidative catabolism of usnic acid is inhibited in thalli floated on the dye. Cyclic AMP reverses this effect.