Enamelysin mRNA displays a developmentally defined pattern of expression and encodes a protein which degrades amelogenin

Previously, a cDNA encoding a novel matrix metalloproteinase (enamelysin) w as isolated from a porcine enamel organ-specific cDNA library, The cloned m RNA is tooth-specific and contains an open reading frame encoding a protein composed of 483 amino acids (Gene, 183:(1-2), p123-128, 1996), Here, we sh ow that: 1) The expression of enamelysin mRNA is not limited to the enamel organ as previously reported. The enamelysin message is also expressed at v ery low levels in the pulp organ. 2) Northern analysis reveals that the ena melysin mRNA displays a developmentally defined pattern of expression in th e enamel organ. The message is expressed at relatively high levels during t he presecretory and early transition stages of development, However, during late maturation, the quantity of enamelysin mRNA is greatly reduced. Conve rsely, the low message levels in the pulp organ remain relatively constant throughout these developmental stages. 3) The enamelysin cDNA was ligated i nto a prokaryotic expression vector and recombinant enamelysin containing a His tag was purified from E. coli. Zymographic analysis utilizing recombin ant murine amelogenin as the substrate, reveals that the purified enamelysi n degrades amelogenin. Since enamelysin is developmentally regulated and is capable of degrading amelogenin, it is likely to play a significant role d uring enamel biomineralization.