Phosphophoryn is the most acidic protein ever discovered and has an isoelectric point of 1.
Many portions of its chain are repeating −D−S−S− (aspartic acid-serine-serine) sequences.
In protein chemistry, net acidity equates to negative charge.
Being highly negative, dentin phosphoprotein is able to attract large amounts of calcium.
In vitro studies also indicate phosphophoryn can initiate hydroxyapatite formation.