Effect of different inhibitors on nonspecific alkaline phosphatase in the microsomal fraction from isolated odontoblasts

Abstract

In the microsomal fraction isolated from rat incisor odontoblasts, the influence of several inhibitors on p-nitrophenyl phosphatase activity (p-NPPase) was demonstrated at pH 10.3 and compared with the influence at pH 8.8. The inhibiting effect of EDTA on the p-NPPase activity was reversed by equimolar concentrations of Zn²⁺. The inhibitory effect of three diphosphonates, ethane-1-hydroxydiphosphonate (EHDP), methanediphosphonate (MDP), and dichloromethanediphosphonate (Cl₂MDP) was equal to that of a chelating agent. Tetramisole and levamisole exerted an inhibitory effect that was different from the complexing type. l-Cystein, but not l-ascorbic acid, inhibited p-NPPase activity with a maximum inhibitory effect at pH 10.5.