[Comparative study of properties of periplasmic and membrane-bound alkaline phosphatase of E. coli]

The properties of three forms of periplasmic and one form of membrane-bound alkaline phosphatase of E. coli were studied. A practically complete agreement between the conditions for optimal activity of these enzymes (pHopt 9.5 +/- 0.1), effect of ionic strength and temperature, and accordance between the substrate specificities (the enzymes decompose all types of phosphate-containing ether bonds) were observed. A similarity was shown between the kinetic parameters (Km = 3.9 x 10(-5) + 4.3 x 10(-5) M) for the reaction of p-nitrophenylphosphate decomposition), type and constants of inhibition (Ki) of these enzymes by phosphate-containing compounds as well as between the values of energy (E = 5.95 + 6.2 kcal/mole) for activation of decomposition of this substrate. A structural similarity of active sites of these enzymes was assumed. It was also suggested that the membrane-bound form of the enzyme is a precursor of the periplasmic one.