Properties of two types of menbrane-bound ATPases,
i. e., plasma membrane ATPase (PL-ATPase) and mitochondrial ATPase (MT-ATPase) in
Zygosaccharomyces rouxii were studied in relation to the salt-tolerance of cells. Km values for ATP were O.7 and 3.3 mM, respectively, for PL-ATPase and MT-ATPase at their respective optimum pH, 6.5 and 8.5. Activities of both ATPases were increased about 2-fold and 6-fold, respectively, by the addition of 10% NaCl to YPD medium. Higher activites were ascribed to increment of the enzyme proteins having the same optimal pHs, Kmvalues, and sensitivities toward various inhibitors. Furthermore, respiratory substrates, such as glycerol and ethanol, increased activities of both ATPase whereas the each ATPase in
Saccharomyces cerevisiae was inversely induced by these substrates. When Z. rouxii cells grown in YPD medium were transferred into NaC1 (10%)-YPD medium, the activity of PL-ATPase was increased rapidly, but that of MT-ATPase increared somewhat slower. Cellular ATP levels were immediately increased to reach about 7-times higher within 1 min, followed by gradual decrease, and cell growth began thereafter. Cellular ATP levels were increased in parallel to the increase of extracellular salinity, and H
+-efflux was enhanced with the increase in cellular ATP level and extracellular salinity.
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