Trypsinogen Amino acid sequence

When trypsin activates chymotry psin, it cleaves chymotrypsinogen at the peptide bonds between amino acids Arg 15 and Do IB. The numbers indicate the amino acid residue sequence numbers, counting from the N-terminal end of the protein. As stated earlier, enterokinase catalyzes the activation of trypsinogen, which begins a cascade of events resulting in the activation of all the pancreatic enzymes... 

The activation of chymotrypsinogen to chymotrypsin involves splitting a polypeptide bond somewhere between the first and the fifteenth amino acid in the N-terminal sequence. As was the case for trypsinogen, the activation involves the rupture of an isoleucyl bond. In fact, in the activation of both trypsinogen and chymotrypsinogen, the first accessible bond in... 

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