Biochemical properties of alkaline phosphatase from endometrial cancer cells

The occurrence of alkaline phosphatase (AP) activity was examined in several human endometrial adenocarcinomas. Catalytic activities were detectable only in 10 out of 15 tumors, with no apparent correlation between elevated AP and histological type. The apparent molecular weight of the enzyme after partial purification was about 140,000 daltons. Kinetic activity, thermodynamic properties and the pH dependence of the activity were in the ranges reported for other subforms. Several other physicochemical properties were also investigated and compared with those displayed by enzymes obtained from normal human tissues. The inhibition studies show that the enzyme shares several properties with the placental form, particularly in resistance to zinc chloride and EDTA action. On the other hand, in sensitivity to uncompetitive inhibitors and to urea and ascorbic acid, it is closer to other non-Regan heat-sensitive forms. The results support the view that a polymorphism in the expression of AP in neoplastic tissues can occur. A wider spectrum of physicochemical properties is clearly needed to define better the characteristics of oncodevelopmental enzymes.