HUMAN PLACENTAL ALKALINE PHOSPHATASE .2. MOLECULAR AND SUBUNIT PROPERTIES OF ENZYME

The molecular and subunit properties of highly purified human placental alkaline phosphatase were investigated. The enzyme was studied at a range of pH values by sedimentation equilibrium, polyacrylamide gel electrophoresis, and immunochemical techniques. Data from these studies indicated that the enzyme was irreversibly denatured at pH 2.3 but was stable as a dimer from pH 4.7 through pH 10.3. At pH 10.5 and above, the enzyme dissociates, principally forming monomer but also forming nmer aggregates. Two different N-terminal groups were demonstrated indicating that the enzyme subunits may not be identical. Optical rotatory dispersion studies showed little α-helix for either the dimer or monomer-dimer form of the enzyme. © 1969.