Phosphophoryn

Phosphophoryn, also known as dentin phosphoprotein (DPP), is a highly acidic, phosphorylated extracellular matrix protein found in dentin, the calcified tissue beneath tooth enamel. It is derived from the dentin sialophosphoprotein (DSPP) gene, which is expressed by odontoblasts during dentinogenesis. The DSPP precursor is secreted and proteolytically cleaved to yield dentin sialoprotein (DSP) and DPP; DPP corresponds to the C-terminal portion of the precursor and is characterized by extreme phosphorylation and high serine-aspartate content.

Phosphophoryn is one of the non-collagenous dentin matrix proteins. It is highly acidic and has a very low isoelectric point, with dozens to hundreds of phosphate groups. Its structure enables strong binding to calcium ions and to hydroxyapatite, promoting nucleation and regulated growth of dentin mineral crystals. It interacts with collagen type I and other dentin matrix molecules, contributing to the organization of the mineralizing matrix.

Functionally, DPP acts as a mineralization regulator, influencing crystal size, orientation, and mineral density during dentin formation. It is thought to serve as a scaffold that concentrates calcium and phosphate at sites of mineral deposition and to modulate the maturation of dentin in developing teeth. Some studies indicate that DPP phosphorylation state affects its mineralization activity.

Mutations in DSPP, including regions encoding DPP, are associated with hereditary dentin defects such as dentinogenesis imperfecta and dentin dysplasia. These conditions reflect disrupted dentin formation and altered mineralization.

Phosphophoryn belongs to the SIBLING family of acidic, secreted matrix proteins involved in biomineralization and is studied for its role in dental biology and tissue engineering.