Figure 2c. Full-length DSPP is an inactive precursor. It is proteolytically processed into DSP and DPP that are from the NH₂-terminal and COOH-terminal regions of DSPP, respectively. DSP is rich in carbohydrates (CHO) but contains fewer phosphates (P), whereas DPP is devoid of glycosylation but contains an unusually large number of phosphates. The phosphates on DPP are mainly present on one side of the protein backbone (George et al., 1996) and are postulated to sequester calcium ions (Ca⁺⁺).