Figure 4. Ameloblastin cleavage sites in vivo and in vitro. Analysis of porcine ameloblastin cleavage products isolated from developing teeth show that ameloblastin is cleaved in vivo after Asn³¹ (a), Gln¹³⁰ (b), Arg¹⁷⁰ (c), Ala²²² (d), Gly³⁰⁰ (e), Arg³¹⁹ (f), and Ala³⁴² (g). Three AMBN cleavage sites targeted by MMP-20 in vitro are identical to known in vivo cleavage sites (after Gln¹³⁰, Arg¹⁷⁰, and A²²²). Two sites that were cleaved in vitro have not been identified in vivo: Pro² (h*) and Gln¹³⁹ (i*). The context of the Gln¹³⁹ site (Q:QV) is identical to the Gln¹³⁰ site, suggesting that this site is likely to be cleaved in vivo, but in vivo cleavage products starting with this cleavage have not yet been described. Key: The in vivo and in vitro AMBN cleavage sites are marked by arrows. The arrows are boxed for the sites cleaved in vitro.