Characterization of protein kinases involved in dentinogenesis

Protein phosphorylation and dephosphorylation control many different cell functions as well as responses to internal and external signals. It has also been shown that highly phosphorylated acidic proteins have an important role in matrix mediated biomineralization, perhaps functioning as nucleators for crystal formation. Dentine phosphoprotein (DPP) is one of such proteins which is exclusively synthesized by the odontoblast cells and therefore a likely candidate to play a significant role in normal and abnormal dentine biomineralization. These studies are directed at characterizing the protein kinases involved in dentinogenesis and in particular the enzyme(s) responsible for DPP phosphorylation. In this report we present data which indicate that there are several different types of kinases in the odontoblast-enriched dental papilla mesenchyme (DPM), some of which can phosphorylate DPP, such as casein kinase I and II. However, a different DPP-kinase activity was identified. This enzyme(s) appears to be different from other reported kinases, and it is the only kinase that can phosphorylate both phosphorylated DPP and enzymatically dephosphorylated DPP.