title: Diminution of outer membrane permeability by Mg2+ in a marine pseudomonad.
abstract: Intact cells of the marine pseudomonad MB-45, in the presence of optimal Mg2+, exhibited little alkaline phosphatase activity as judged by the hydrolysis of p-nitrophenylphosphate. Sonic extracts, in contrast, were rich in this activity. Removal of the loosely bound outer layer did not diminish this crypticity of alkaline phosphatase, but decreasing the concentration of Mg2+ in the suspending medium progressively exposed the alkaline phosphatase. Since MB-45 did not liberate alkaline phosphatase into the surrounding medium even in the absence of Mg2+ and since this enzyme is localized in the periplasmic space, it can be concluded that the crypticity was due to the exclusion of p-nitrophenylphosphate by the outer membrane. Mg2+ is apparently essential for the full expression of this limited permeability.
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects*; D002474:Cell-Free System; D007700:Kinetics; D009596:Nitrophenols; D010755:Organophosphates / Q000378:metabolism; D011549:Pseudomonas / Q000201:enzymology / Q000378:metabolism*; D012623:Seawater; D012965:Sodium Chloride / Q000494:pharmacology; D014871:Water Microbiology
chemical_list: D009596:Nitrophenols; D010755:Organophosphates; D012965:Sodium Chloride; D000469:Alkaline Phosphatase