I have a peptide sequence with no prolines, 2 positively charged residues at the c-terminal ends of 2 fragments created by trypsin cleavage, but shows no fragments from carboxypeptidases A or B. I thought if a positively charged residue was the c-terminal end of the primary peptide, then I should have seen fragments from carboxypeptidase B, since there is no blocking proline by either the Arg or Lys. I am stumped--what am I missing?© BrainMass Inc. brainmass.com October 2, 2020, 1:14 am ad1c9bdddf
Carboxypeptidase B cleaves away the last amino acid of your sequence if it is basic. Since you saw no fragments ...
In this solution a proteolysis scheme using carboxypeptidases A and B is used to determine properties of a peptide. This is in an effort to help determine the protein sequence