Astacin proteases cleave dentin sialophosphoprotein (Dspp) to generate dentin phosphoprotein (Dpp).

[dentin dysplasia]

Dentin sialophosphoprotein (Dspp ) is critical for proper dentin biomineralization because genetic defects in DSPP cause dentin dysplasia type II and dentinogenesis imperfecta types II and III . Dspp is processed by proteases into smaller subunits ; the initial cleavage releases dentin phosphoprotein (Dpp ). We incubated fluorescence resonance energy transfer (FRET ) peptides containing the amino acid context of the Dpp cleavage site (YEFDGKSMQGDDPN , designated Dspp-FRET ) or a mutant version of that context (YEFDGKSIEGDDPN , designated mutDspp-FRET ) with BMP-1 , MEP 1 A , MEP 1 B , MMP-2 , MMP-8 , MMP-9 , MT 1 -MMP , MT 3 -MMP , Klk 4 , MMP-20 , plasmin , or porcine Dpp and characterized the peptide cleavage products . Only BMP-1 , MEP 1 A , and MEP 1 B cleaved Dspp-FRET at the G-D peptide bond that releases Dpp from Dspp in vivo . We isolated Dspp proteoglycan from dentin power and incubated it with the three enzymes that cleaved Dspp-FRET at the G-D bond . In each case , the released Dpp domain was isolated , and its N-terminus was characterized by Edman degradation . BMP-1 and MEP 1 A both cleaved native Dspp at the correct site to generate Dpp , making both these enzymes prime candidates for the protease that cleaves Dspp in vivo . MEP 1 B was able to degrade Dpp when the Dpp was at sufficiently high concentration to deplete free calcium ion concentration . Immunohistochemistry of developing porcine molars demonstrated that astacins are expressed by odontoblasts , a result that is consistent with RT-PCR analyses . We conclude that during odontogenesis , astacins in the predentin matrix cleave Dspp before the DDPN sequence at the N-terminus of Dpp to release Dpp from the parent Dspp protein .

Diseases
Validation

Diseases presenting "calcium ion concentration" symptom

dentin dysplasia

dentinogenesis imperfecta

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