Key proteolytic cleavage site and full-length form of DSPP

It is known that dentin sialophosphoprotein (dspp) is processed into nh2- and coohterminal fragments,but its key cleavage site has not been identified,nor has its full-length form been discovered. the objectives of this study were to identify the key cleavage site during dspp processing and to search for full-length dspp in vivo. we generated a construct encoding dspp,in which asp452,a cleavage site residue,was replaced by ala 452. the pulp-odontoblast complex and dentin were extracted,chromatographically separated,and assessed by stains-all staining,western immunoblotting,and mass spectrometry. these studies showed that the substitution of asp452 by ala452 completely blocks the cleavage of mouse dspp in the transfected cells,indicating that the nh 2-terminal peptide bond of asp452 is essential for the initiation of dspp proteolytic processing. the results of this study revealed the presence of full-length dspp and its processed fragments in extracts from the pulp/odontoblast and dentin.