Structure
Enamelin is thought to be the oldest member of the enamel matrix protein (EMP) family, with animal studies showing remarkable conservation of the gene phylogenetically. All other EMPs are derived from enamelin, such as amelogenin. EMPs belong to a larger family of proteins termed 'secretory calcium-binding phosphoproteins' (SCPP). Similar to other enamel matrix proteins, enamelin undergoes extensive post-translational modifications (mainly phosphorylation), processing, and secretion by proteases. Enamelin has three putative phosphoserines (Ser54, Ser191, and Ser216 in humans) phosphorylated by a Golgi-associated secretory pathway kinase (Function
The primary function of the proteins acts at the mineralisation front; growth sites where it is the interface between the ameloblast plasma membrane and lengthening extremity of crystals. The key activities of enamelin can be summarised: * Necessary for the adhesion of ameloblasts to the surface of the enamel in the secretory stage * Binds to hydroxyapatite and promotes crystallite elongation * Act as a modulator for ''de novo'' mineral formation It is speculated that this protein could interact with amelogenin or other enamel matrix proteins and be important in determining growth of the length of enamel crystallites. The mechanism of this proposed co-interaction is synergistic (" Goldilocks effect"). With enamelin enhancing the rates of crystal nucleation via the creation of addition sites for EMPs, such as amelogenin, to template calcium phosphate nucleation. It is best thought to understand the overarching function of enamelin as the proteins responsible for correct enamel thickness formation.Clinical significance
Mutations in the ''ENAM'' gene can cause certain subtypes of amelogenesis imperfecta (AI), a heterogenous group of heritable conditions in which enamel in malformed. Point mutations can cause autosomal-dominant hypoplastic AI, and novel ''ENAM'' mutations can cause autosomal-recessive hypoplastic AI. However, mutations in the ''ENAM'' gene mainly tend to lead to the autosomal-dominant AI. The phenotype of the mutations are generalised thin enamel and no defined enamel layer. A moderately higher than usual ''ENAM'' expression leads to protrusive structures (often, horizontal grooves) on the surface of enamel, and with high transgene expression, the enamel layer is almost lost.See also
* Ameloblastin * Amelogenin * Amelogenesis * Amelogenesis imperfectaReferences
Further reading
* * * * * * * * * * *External links
* * {{UCSC gene details, ENAM Proteins Dentistry Biomineralization Teeth