Suppose you add the two peptide sequences shown below to the enzyme chymotrypsin in a buffered solution that is composed of entirely of 'heavy' water (H218O)*. After adding the peptides to the chymotrypsin solution, using a mass spectrometer you observe that the mass of peptide 1 has shifted by two mass units (Daltons) relative to its normal mass. The mass of peptide 2 is unaffected. If you add these peptides to the same heavy water buffer without chymotrypsin present, neither peptide shows a mass shift. Explain this result based on what we know about chymotrypsin.