Description of Two Classes of Proteinases from Enamel Extracellular Matrix Cleaving a Recombinant Amelogenin

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Abstract
This paper is a short review of our recent studies on amelogenin proteolysis in vitro using a recombinant mouse amelogenin M179 as a substrate. The specific aims of this study were to identify, isolate and characterize the proteinases in the enamel extracellular matrix. We identified two classes of enamel proteinases; 1) the high molecular weight proteinase (60-68 kDa) cleaves the c-terminal segment of M179 and is a calcium dependent metalloproteinase with an optimum pH of 8.2) The low molecular weight proteinase (approximately 30 kDa) removes the TRAP (Tyrosine Rich Amelogenin Polypeptide) sequence and causes further degradation of M179. The latter was identified to be a serine proteinase with an optimal activity at pH 6. These data support the notion that enamel proteinases cleave amelogenin through specific and highly controlled mechanisms and that they may fulfill direct roles during enamel maturation.