The 5'-Nucleotidase of Escherichia coli

Escherichia coli 5'-nucleotidase has been shown to be a constitutive enzyme uninfluenced by the phosphate, sugar, or ionic content of the growth medium. It is a periplasmic located enzyme. 5'-Nucleotidase activities stimulated by Co++, with pH optima of 5.7 to 6.0, have been partially purified from Aerobacter aerogenes, Shigella sonnei, and Salmonella typhimurium. A specific protein inhibitor for the 5'-nucleotidase has been found in the cell cytoplasm. It inhibits the 5'-AMP, ATP, and uridine diphosphate glucose activity of the 5'-nucleotidase of E. coli and also inhibits the 5'-AMP hydrolysis of 5'-nucleotidases of A. aerogenes, S. sonnei, and S. typhimurium. The inhibitor is heat-labile at 45°. It combines with the 5'-nucleotidase at 0° as well as at 21°. Inhibitory activity is altered only by urea and is not affected by mercaptoethanol or metals.