Fig. 2.

In vitro enzymatic assays with Fra1 aminopeptidase and peptide substrates. (A) HPLC analyses of proteolysis by Fra1. Peptides (S)PSKMNA, (A)PVTIEK, (PP)PTAQF, and (V)PVTIEK were converted by Fra1 to products through the removal of residues in parentheses. (B) The trimming of PPPTAQF to PTAQF by Fra1 was processive since the levels of the PPTAQF intermediate were negligible or nearly so, indicating that the cleavage that generates PPTAQF was nearly immediately followed by the next and last cleavage.