Fluoride alters casein kinase II and alkaline phosphatase activity in vitro with potential implications for dentine mineralization.
Dentine phosphoprotein (DPP), a major non-collagenous acidic protein of dentine, undergoes altered phosphorylation in vivo in the presence of high fluoride concentrations. This has major implications for the altered mineralization patterns found during fluorosis. In dentine, casein kinase II is involved in phosphorylating DPP, and alkaline phosphatase (ALP) is ascribed roles in the dephosphorylation of DPP, increasing the inorganic phosphate at the mineralization front and the removal of pyrophosphate. Here the influence of fluoride in vitro on the activity of purified casein kinase II and ALP and its relation to altered patterns of mineralization were examined. Kinetic analysis showed that casein kinase II activity was completely inhibited at 0.04 M NaF. Vmax when compared to the control assay was significantly decreased (P < 0.0001) between concentrations 4 x 10(-4)-4 x 10(-8) M NaF. Significant changes to the Km (P < 0.0001) were also observed. ALP activity was inhibited by NaF (0.09-9 x 10(-8) M), with Vmax significantly decreased (P < 0.0001) at 0.09 M NaF. Alterations in the activity of these enzymes in the presence of fluoride may in part explain the decreased phosphorylation observed in DPP isolated from fluorotic dentine and may aid understanding of the altered matrix mediated mineralization patterns found during fluorosis.
Department of Basic Dental Science, Dental School, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XY, UK. milan@cardiff.ac.uk
A M
AM
Milan
R J
RJ
Waddington
G
G
Embery
D000469:Alkaline Phosphatase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000818:Animals; D047390:Casein Kinase II; D003804:Dentin / Q000187:drug effects* / Q000201:enzymology; D003810:Dentinogenesis / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D005459:Fluorides / Q000008:administration & dosage / Q000494:pharmacology*; D009050:Fluorosis, Dental / Q000201:enzymology; D007700:Kinetics; D016014:Linear Models; D008322:Mammals; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011869:Radioligand Assay; D013053:Spectrophotometry; D018709:Statistics, Nonparametric; D014074:Tooth Calcification / Q000187:drug effects*
D016326:Extracellular Matrix Proteins; D010750:Phosphoproteins; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; D000469:Alkaline Phosphatase; D005459:Fluorides