Dentin phophoprotein, or phosphophoryn, is one of three proteins formed from dentin sialophosphoprotein

Dentin sialophosphoprotein (protein)

Dentin sialophosphoprotein is the only protein produced uniquely by odontoblasts, the cells that produce tooth dentin. It is a non-collagenous SIBLING protein that is later cleaved into three functional proteins: dentin phosphoprotein , taken from the C-terminal end, dentin sialoprotein from the...

 and is important in the regulation of mineralization

Mineralization (biology)

In biology, mineralization refers to the process where an organic substance is converted to an inorganic substance.This may also be a normal biological process which takes place during the life of an organism such as the formation of bone tissue or egg shells, largely with calcium.This term may...

 of dentin

Dentin

Dentine is a calcified tissue of the body, and along with enamel, cementum, and pulp is one of the four major components of teeth. Usually, it is covered by enamel on the crown and cementum on the root and surrounds the entire pulp...

.

Phosphophoryn is the most acidic protein ever discovered and has an isoelectric point

Isoelectric point

The isoelectric point , sometimes abbreviated to IEP, is the pH at which a particular molecule or surface carries no net electrical charge....

 of 1. This extreme acidity is achieved by its amino acid

Amino acid

Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

 sequence. Many portions of its chain are repeating -D-S-S- (aspartic acid-serine

Serine

Serine is an amino acid with the formula HO2CCHCH2OH. It is one of the proteinogenic amino acids. By virtue of the hydroxyl group, serine is classified as a polar amino acid.-Occurrence and biosynthesis:...

-serine) sequences. In protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 chemistry, net acidity equates to negative charge. Being highly negative, dentin phosphoprotein is able to attract large amounts of calcium

Calcium

Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

. In vitro studies also indicate phosphophoryn can initiate hydroxyapatite formation.