The action of F- on human alkaline phosphatases obtained from human fetal parietal bones

Abstract— Human fetal (age 8–14 weeks) parietal bones were homogenated and subjected to two different chromatographic procedures. Three distinct alkaline phosphatase enzyme preparations were obtained with DEAE-cellulose ion-exchange chromatography and six different alkaline phosphatase enzyme preparations with DEAE-cellulose ion-exchange chromatography and gel permeation chromatography on Sephadex G-200. F^- (as NaF or KF) caused a slight inhibition of the enzymic hydrolysis reaction of p-nitrophenyl phosphate produced by the three enzyme preparations, allowing calculation of the inhibition constants (Ki). When Mg²⁺ was present in the incubation media, no valid inhibition constants could be calculated for fluoride because of a non-linearity of the experimental values. The other six enzyme preparations were, however, completely unaffected by the F^- whether Mg²⁺ was present or not until a 0.166 ×10^-1 M F^- concentration level was reached in the incubation media. The F^- was still ineffective when other substrates such as Na₄P₂O₅ and α-naphthyl phosphate were used instead of p-nitraphenyl phosphate. F^- produced, however, a slight activation of the enzymic hydrolysis reaction of both p-nitrophenyl phosphate and α-naphthyl phosphate catalyzed by some enzyme preparations when phosphate was added to the incubation media.