Which of the following is the major protein of enamel:
Enamel proteins constitute about 1% of the organic component of enamel. These proteins are broadly categorized into amelogenins and non-amelogenins. Among these two amelogenins (AMEL) contribute to nearly 90% of all the enamel proteins and the rest 10% by non-amelogenins.
These are low molecular weight proteins and are rich in proline, histidine, glutamine, and leucine. These amelogenins accumulate during the secretory stage of ameloblasts. Amelogenins (AMEL) are coded by two genes, namely AMELX and AMELY which are located on the X and Y chromosomes. Amelogenins regulate the orientation, shape, and length of apatite crystals mainly by preventing the crystals from fusing with each other thus enhancing the crystal growth. Any mutation in amelogenins - AMELX results in amelogenesis imperfecta or defect in this protein gene may lead to reduced enamel thickness.
It includes ameloblastin (AMBN), enamelin (ENAM), amelotin (AMTN), tuftelin. All these non-amelogenins are high molecular weight proteins and are rich in glycine, aspartic acid, and serine.
Ameloblastin (AMBN) is the second most abundant enamel protein. Ameloblastin promotes the mineral formation and crystal elongation and is produced during the secretory phase of ameloblasts.
Enamelin (ENAM) is a glycoprotein that interacts with the amelogenin and other matrix proteins to aid in crystal nucleation and growth. The enamelin is also formed during the secretory phase of ameloblasts.
Tuftelin is a localized protein seen at dentino enamel junction (DEJ) and it serves as the nucleator of de novo crystal formation.
Amelotin (AMTN) is a recently discovered glycoprotein. Amelotin is secreted during the maturation phase of ameloblasts and helps in the late stages of enamel mineralization.