Figure 3. Predicted cleavage of human enamelin, based upon known porcine enamelin cleavage products. The amino acid numbers are shown above the rectangle, which represents the enamelin protein. The black rectangle represents the signal peptide (amino acids 1–39). The dotted rectangles represent cleavage products that have not been characterized at the C-terminus and are therefore shown with a question mark in the amino acid position. Enamelin is initially secreted as a 186-kDa species that undergoes rapid proteolysis to form a variety of cleavage products.