MOLECULAR-CLONING AND MESSENGER-RNA TISSUE DISTRIBUTION OF A NOVEL MATRIX METALLOPROTEINASE ISOLATED FROM PORCINE ENAMEL ORGAN

A cDNA encoding a novel matrix metalloproteinase (MMP) was isolated fr om a porcine enamel organ-specific cDNA library. Multiple tissue north ern blot analysis revealed the presence of two mRNA transcripts which were expressed only in the enamel organ. The transcripts were 1968 bp or 3420 bp in length and resulted from the utilization of alternative polyadenylation sites. The open reading frame of the cloned mRNA encod es a protein composed of 483 amino acids. The MMP has a predicted mole cular mass of 54.1 kDa, which is similar to that of the stromelysins o r collagenases, although it is not a member of either of these two cla sses of MMPs. A motif analysis revealed that the cloned MMP does not c ontain a consensus hemopexin-like domain because it lacks a critical t ryptophan and proline residue at the appropriate positions. Since the cloned MMP is a new member of the MMP gene family and its expression a ppears limited to the enamel organ, we have named it enamelysin.