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Figure 3. Hypothetical processing of DMP1 and DSPP by PHEX protein. DMP1 and DSPP are converted to functional fragments by PHEX enzyme on the surfaces of osteoblasts, osteocytes, and odontoblasts. PHEX protein, one of the M13 endopeptidases, has a short cytoplamic NH2-terminal region, a single transmembrane domain, and a long extracytoplasmic domain that contains the active site of the enzyme (Crine et al., 1997). After DMP1 and DSPP are processed by cleavage of selected X-Asp bonds, their fragments—namely, 37K, 57K, DSP, and DPP—are transported to the ECM of bone and dentin, where they influence mineralization.
