Figure 7. Digestion of the 32-kDa enamelin by enamelysin (MMP-20) and kallikrein 4 (KLK4). The 32-kDa enamelin, the 25-kDa amelogenin, MMP-20, and KLK4 were isolated from developing pig teeth. Cleavage of the 32-kDa enamelin by MMP-20 was not detected even after 72 hrs of incubation at a substrate:enzyme ratio of 50:1 (w/w). MMP-20 did digest amelogenin (data not shown). KLK4 fully degraded the 32-kDa enamelin after 24 hrs of incubation at a substrate:enzyme ratio of 100:1 (w/w).