Purified chymase and CathG cleave CTAP-III but not PF-4. Human chymase (Chy; 250 ng/mL) purified from mast cells (left panels) or human CathG (500 ng/mL) purified from neutrophil granulocytes (right panels) were incubated with either 3 μM CTAP-III (top row) or 4 μM PF-4 (bottom row) in processing buffer for 0 minutes (solid line) or 120 minutes (broken line) at 37°C. The products were separated, detected by their absorbance at 214 nm, and fractionated by reverse-phase HPLC using a linear gradient of acetonitrile in 0.1% TFA (dashed line) as described in “Materials and methods.” Fractions containing protein peaks eluting at retention times of 23.0 minutes, 22.2 minutes, 16.6 minutes, and 25.4 minutes were analyzed by ESI-FT-MS and identified by their respective mass of 9286 amu, 7623 amu, 1682 amu, and 7764 amu as CTAP-III, NAP-2, CTAP-III[1-15], and PF-4, respectively. One representative experiment of 3 is shown.