Figure 2. Comparison of the binding affinities of active rhMMP20 for amelogenin peptides by peptide competition assays. The fluorescence intensity observed in a peptide competition assay was directly related to the amount of digested quenched peptides. Therefore, the fluorescent signal was inversely related to the affinity of active rhMMP20 for the competitor peptides (A1 or M1), which competed with the quenched peptide for binding to MMP20. The reaction without any competitors (QP+MMP20) had the highest RFU readings (curve’s slope = 12.34 ± 0.31, n = 3). The wild-type A1 peptide (A1+QP+MMP20) is a significantly stronger competitor (curve’s slope = 8.29 ± 0.46, n = 3) than M1 peptide (M1+QP+MMP20), containing a P-to-T mutation (curve’s slope = 11.14 ± 0.64, n = 3). QP, quenched peptide; A1, peptide without mutation; M1, peptide with mutation; RFU, relative fluorescence units. *p < 0.05. **p < 0.01.