title: Functions of KLK4 and MMP-20 in dental enamel formation.
abstract: Two proteases are secreted into the enamel matrix of developing teeth. The early protease is enamelysin (MMP-20). The late protease is kallikrein 4 (KLK4). Mutations in MMP20 and KLK4 both cause autosomal recessive amelogenesis imperfecta, a condition featuring soft, porous enamel containing residual protein. MMP-20 is secreted along with enamel proteins by secretory-stage ameloblasts. Enamel protein-cleavage products accumulate in the space between the crystal ribbons, helping to support them. MMP-20 steadily cleaves accumulated enamel proteins, so their concentration decreases with depth. KLK4 is secreted by transition- and maturation-stage ameloblasts. KLK4 aggressively degrades the retained organic matrix following the termination of enamel protein secretion. The principle functions of MMP-20 and KLK4 in dental enamel formation are to facilitate the orderly replacement of organic matrix with mineral, generating an enamel layer that is harder, less porous, and unstained by retained enamel proteins.
authors.affiliation: Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, 1011 North University, Ann Arbor, MI 48109-1078, USA.
authors.forename: Yuhe
authors.initials: Y
authors.lastname: Lu
authors.forename: Petros
authors.initials: P
authors.lastname: Papagerakis
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Yamakoshi
authors.forename: Jan C-C
authors.initials: JC
authors.lastname: Hu
authors.forename: John D
authors.initials: JD
authors.lastname: Bartlett
authors.forename: James P
authors.initials: JP
authors.lastname: Simmer
mesh_terms: D000818:Animals; D003743:Dental Enamel / Q000166:cytology / Q000201:enzymology / Q000254:growth & development* / Q000378:metabolism*; D006801:Humans; D007610:Kallikreins / Q000378:metabolism*; D053519:Matrix Metalloproteinase 20 / Q000378:metabolism*; D014070:Tooth / Q000166:cytology / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism
chemical_list: D007610:Kallikreins; C120801:kallikrein 4; D053519:Matrix Metalloproteinase 20