Mercaptoethanol and dithiothreitol decrease the difference of electrochemical proton potentials across the yeast plasma and vacuoar membranes and activate their H + ‐ATPases

Mercaptoethanol and dithiothreitol (DTT) inhibited the acidification of external medium by by Saccharomyces Carlsbergensis cells and protoplasts during glucose oxidation. The inhibition was also observed when cells were incubated with mercaptoethanol or when mercaptoethanol and DTT were used to prepare protolasts. Experiments with S. carlsbergensis plasma membrene vesicles and vacuoles showed these thiol reagents to inhibitATP‐dipendent generation of ΔpH and E m across plasma membrane vesicles and vacuoles but to activate their H + ‐ATPases. Mercaptoethanol and DTT are suggested to de‐energize plasmalemma as well as tonoplast by increasing their H + ‐permeability and to disturb the cell ion homeostasis.