Alkaline phosphatase with broad substrate specificity. a phosphate monoester + H2O = an alcohol + phosphate Binds 2 Zn(2+) ions. Subject to competitive inhibition by phosphate. Inhibited by manganese. Magnesium mildly increases enzyme activity when the zinc concentration is suboptimal. Optimal activity is dependent on the presence of 0.01-2% Triton X-100. Triton X-100 at a concentration of 0.05% increases the activity about fivefold relative to that in its absence. The enzyme is even active in Triton X-100 concentrations up to 80%. 50% inhibition by 4 mM EDTA and 50% inhibition by 48 mM sodium citrate. Optimum pH is 7-10. Activity on 4-nitrophenyl phosphate is observed between pH 6 and pH 11. Heat-labile. Activity increases with temperature between 15 and 35 degrees Celsius and decreases with further heating. No activity at 65 degrees Celsius. Preincubation for 10 minutes at 50 or 60 degrees Celsius causes 50% or 100% inactivation, respectively. Heat-inactivated enzyme cannot be renaturated. Associated with the periplasmic side of the inner membrane.