Fluoride does not inhibit enamel protease activity

Fluorosed enamel can be porous,mottled,discolored,hypomineralized,and protein-rich if the enamel matrix is not completely removed. proteolytic processing by matrix metalloproteinase-20 (mmp20) and kallikrein-4 (klk4) is critical for enamel formation,and homozygous mutation of either protease results in hypomineralized,protein-rich enamel. herein,we demonstrate that the lysosomal proteinase cathepsin k is expressed in the enamel organ in a developmentally defined manner that suggests a role for cathepsin k in degrading re-absorbed enamel matrix proteins. we therefore asked if fluoride directly inhibits the activity of mmp20,klk4,dipeptidyl peptidase i (dppi) (an in vitro activator of klk4),or cathepsin k. enzyme kinetics were studied with quenched fluorescent peptides with purified enzyme in the presence of 0-10 mm naf,and data were fit to michaelis-menten curves. increasing concentrations of known inhibitors showed decreases in enzyme activity. however,concentrations of up to 10 mm naf had no effect on klk4,mmp20,dppi,or cathepsin k activity. our results show that fluoride does not directly inhibit enamel proteolytic activity. © 2011 international & american associations for dental research.