Osservazioni prellminari sul meccanismo di azione della cocliobolina

Abstract

Abstract MECHANISM OF COCHLIOBOLIN ACTIVITY: A PREVENTIVE NOTE. — Coch-liobolin caused leakage of phosphate and organic compounds from corn rootlets and potato discs, at room temperature. The leakage does not occur at 1–5°C, but when potato discs are incubated at this temperature and then thoroughly washed and brought at 25°C, a sharp increase of phosphate may be noticed in the incubation solutions. Cochliobolin inhibited partially the aerobic respiration of glucose and endogenous carbon in Micrococcus pyogenes var. aureus resting cells. Aerobic respiration of pyruvate, succinate, fumarate and malate was completely inhibited, while the inhibition of lactate and Lketoglutarate respiration required a short lag period. The hydrogen-ion concentration of the media seemed to be an important factor controlling the rapidity of action of the inhibitor, because at pH 4 and 5 at least 120 minutes were required prior any effect could be observed, while only 30 minutes were required at pH 6. The effects of cochliobolin on Micrococcus resting cells were irreversible In contrast, respiratory activities of acetonic powders were refractory to the substance under aerobic conditions, and oxidation of pyruvate, malate, fumarate, succinate and α-ketoglutarate were not affected by saturated solutions of cochliobolin. It is suggested that the first site of attack is the cell wall-cell membrane unit, altering cell permeability, so that inorganic ions and other cofactors essential to respiration are lost in consequence of the leakage through the cell membrane.