You are sequencing a polypeptide chain. You digest the polypeptide with trypsin to generate a mixture of six peptide fragments. You sequence the six peptides and come up the following sequences:
M-G-P-A-D-L-I-R H-V-E-S-K D-T-C-K-M-R A-A-E-Y
H-H-F H-G
From the sequence of the five peptides, you suspect that the trypsin you used to digest the original polypeptide was contaminated with another enzyme. What enzyme is contaminating your trypsin enzyme stock? Explain how you came to this conclusion.