Characterization of plasma membrane proton‐ATPase from salt‐tolerant yeast Zygosaccharomyces rouxii cells

Plasma membrane was isolated from the salt‐tolerant yeast Zygosaccharomyces rouxii and from Saccharomyces cerevisiae. The ATPase in the plasma membrane of Z. rouxii cells was a typical proton‐ATPase as judged by testing with various ATPase inhibitors. There were slight differences in the pH optima of activities and in the sensitivity to sodium chloride (NaCl) and potassium chloride (KCl) of the ATPase from Z. rouxii and S. cerevisiae. The specific ATPase activity from Z. rouxii was higher in cells grown in a medium containing 2 M‐NaCl than in those not containing NaCl. No in vivo activation by incubation with glucose was observed in Z. rouxii cells and the specific ATPase activity was independent of the growth phase, unlike S. cerevisiae cells.