Alkaline and acid phosphatases from the extensively halotolerant bacterium Halomonas elongata

Alkaline and acid phosphatases (EC 3.1.3.1 and EC 3.1.3.2, respectively) of Halomonas elongata were cytochemically localized on the cell envelope. These enzymes were then isolated and partially purified by sonication, ammonium sulfate precipitation, and column chromatography from cells grown in alanine defined medium at 0.05, 1.37, and 3.4 M NaCl. Enzyme assays were conducted at pH 5.0 and 9.0 with varying concentrations of NaCl, KCl, and LiCl in the assay buffer. Results showed higher acid phosphatase activity compared with that of alkaline phosphatase; and all enzyme activities were optimal at NaCl concentrations similar to the medium NaCl concentrations for the cells grown at 1.37 and 3.4 M. However, minimum enzyme activities were observed for cells grown at the low salt concentration (0.05 M). Although samples showed strong activities at some KCl concentrations, generally the enzyme activities decreased significantly when KCl or LiCl was substituted for NaCl. Polyacrylamide gel electrophoresis followed by histochemical staining for the phosphatases showed only one band for both enzymes for each cell sample grown at the different NaCl concentrations.