Vibrio parahaemolyticus utilized ATP, ADP or AMP as the sole source of carbon. About three times higher activity of membrane-bound 5'-nucleotidase was observed in cells grown in the presence of these nucleotides than in their absence: and therefore the enzyme seems to be inducible. Since the 5'-nucleotidase activity could be measured with whole cells, the active site of this enzyme appears to be outwardly oriented. Both Mg2+ and Cl- were required for activity. Among the divalent cations tested, Mn2+ and Co2+ could replace Mg2+ to some extent, whereas Zn2+ strongly inhibited activity. Among the anions tested, Br-, I- and NO3- could replace Cl-, but SO4(2-) and CH3COO- could not. When cells were grown with ATP, Cl- was indispensable and Zn2+ strongly inhibited growth. Therefore, it is concluded that extracellular ATP and other 5'-nucleotides are cleaved by the membrane-bound 5'-nucleotidase outside the cells and that the adenosine produced is then utilized.
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