Effect of 2–6 Dinitrophenol on Yeast Respiration.∗

Abstract

Undissociated 2–4 dinitrophenol (alpha-DNP) stimulates yeast respiration 1 ,²,³ and fermentation. 1 We have undertaken a survey of the action of the isomers of this substance, the first studied being 2–6 dinitrophenol (beta-DNP). The experimental procedure has been described elsewhere. 1 , 2

Beta-DNP resembles alpha-DNP in that only the undissociated acid affects yeast metabolism. The action is less intense, in that optimal doses of alpha-DNP cause approximately 100% increase in the rate of oxygen consumption, while the beta form raises the respiratory rate by about 50% in optimal doses. Similar relations have been demonstrated in the capacities of these substances to induce hyperthermia in the pigeon. 4 The optimal concentration of beta-DNP at pH 5.4 and at pH 6.0 in glucose phosphate solutions is about 1.4 mg. of the undissociated acid per liter.

Like alpha-DNP, beta-DNP rapidly induces either stimulation or inhibition, depending upon concentration. The effect develops within 5 minutes.

Inhibition of respiration by beta-DNP is reversible, as is the similar inhibition by alpha-DNP.

A slight further increase over the beta-DNP optimum can be evoked by addition of alpha-DNP. Addition of optimal concentration of beta-DNP to yeast suspensions in which the alpha-DNP concentration is optimal causes a decrease in the alpha-DNP effect. Further studies on these interrelations are in progress.

Like alpha-DNP, the action of beta-DNP does not depend upon the presence of glucose, but unlike alpha-DNP the usual stimulation pattern in phosphate buffer at pH 5.4 is not obtained in acetate buffer at DH 5.4.