Now, Pi chymatrypsin is not yet a fully functional enzyme. What Pi Chimetrypsin does is it goes on to other Pi Chimetrypsin molecules and it cleaves those molecules at several sites. And what it does is it ultimately removes two dipeptides from this molecule. So it removes a dipeptide from this region to basically remove two amino acids. That's why we go from 15 to 13 and we also cleave in this section and we remove a dipeptide. And so that's why we have two amino acids missing in this section.