Cathespin C is a dipeptidyl aminopeptidase that can sequentially remove dipeptides from a peptide chain with an unsubstituted N-terminus. The enzyme exhibits a preference for glycine and proline as N-terminal aminoacids. Substrates that have an N-terminal lysyl or arginyl residue, or a penultimate proryl residue are not targeted by this enzyme. The endopeptidase activity requires the presence of halide ions and sulfydryl activators.