Release of alkaline phosphatase from cells of Pseudomonas aeruginosa by manipulation of cation concentration and of pH

Abstract

Pseudomonas aeruginosa ATCC 9027 contains an inducible alkaline phosphatase. The enzyme is readily removed from 14-hr cells by washes in 0.2 m MgCl(2), pH 8.4. Similar washes in tris(hydroxymethyl)aminomethane buffer, 20% sucrose, monovalent ions, or water partially release enzyme from the cells. The release of alkaline phosphatase is correlated with an increased release of protein and retention of internal enzymes. The effect of 0.2 m MgCl(2) washing upon the cells is minimal since both viability and growth rates remain unchanged as compared to water washing. Although cells are plasmolyzed in both 0.2 m MgCl(2) and 20% sucrose, it is evident that plasmolysis alone is unable to account for total enzyme release and that a divalent metal, i.e. Mg(2+), augments the release pattern. Growing cells in the presence of increasing concentrations of MgCl(2) or at increased pH values results in an almost total secretion of the enzyme to the culture filtrate. The findings suggest that P. aeruginosa alkaline phosphatase is linked to the exocytoplasmic region through divalent metal ion, presumably Mg(2+), bridges.