Figure 12.

Proteolysis of porcine DSPP. Numbers indicate cleavage sites discovered by characterizing DSPP-derived cleavage products. DSPP is first processed by BMP-1 to generate DSP–DGP complex and DPP. Then, DSP–DGP is further cleaved in the dentin extracellular matrix by MMP-2 and MMP-20, generating DSPs and DGPs. MMP-20 performs the cleavage that separates DSP and DGP (at Ser³⁹²) and generates N-terminal DSP cleavage products. On the other hand, MMP-2 cleaves DSP–DGP primarily within the C-terminal region of the DSP (at Ser³⁴⁵ and Ile³⁷⁷), releasing DGP-containing cleavage products. The mechanism of DPP degradation in vivo is unknown.