CONTROL OF MUCIN MOLECULAR-FORMS EXPRESSION BY SALIVARY PROTEASE - DIFFERENCES WITH CARIES

1. A protease activity capable of degradation of the high mol. wt sali vary mucus glycoprotein to a low mol. wt glycoprotein form was identif ied in human submandibular gland secretion. 2. The protease exhibited optimum activity at pH 7.0-7.4, and gave on SDS-PAGE under reducing co nditions two major protein bands of 48 and 53 kDa. The enzyme showed s usceptibility to PMSF, alpha1antitrypsin, and egg white and soybean in hibitors, a characteristic typical to serine proteases. 3. The activit y of the protease towards the high mol. wt mucus glycoprotein was foun d to be 3.8-fold higher in submandibular gland secretion of caries-res istant individuals than that of caries-susceptible. Furthermore, the e nzyme from both groups displayed greater activity against the mucus gl ycoprotein of caries-resistant subjects. 4. Since the low mol. wt sali vary mucus glycoprotein form is more efficient in bacterial clearance than the high mol. wt mucin, the enhanced expression of this indigenou s salivary protease activity towards mucin may be the determining fact or in the resistance to caries.