Comparative Biochemical Studies of Placental Alkaline Phosphatase in Animals

Abstract

Biochemical properties of alkaline phosphatase (ALP) from placenta were compared between man, dog, cat, rabbit and cattle. 1) Optimum pH of the enzyme was essentially identical through the species of the animals but the inhibition by L-phenylalanine was clearly demonstrable with human ALP but little with that of other animals. 2) ALP of human placenta was not inactivated by heating at 65°C for 15 min, but one of the other animals was thermolabile. Such thermostability of human placental ALP almost disappeared after treatment with EDTA, suggesting that the divalent metal ions were required for the thermostability. 3) Activities of placental ALP were inhibited by cationsurfactants in human and rat but not in the other animals, while the inhibition by DOC-Na, an anion-surfactant, was seen only in human. 4) The affinity to β-glycerophosphae of placental ALP was seen only in human.