Purification and characterization of PK-120, a novel substrate for plasma kallikrein, from guinea pig plasma.

PK-120 is a novel substrate of plasma kallikrein isolated from human plasma. Western blotting using anti-human PK-120 polyclonal antibodies demonstrated the presence of a PK-120-like protein in guinea pig, rat and mouse plasma. We purified the immunoreactive-120 kDa protein from guinea pig plasma by polyethylene glycol fractionation followed by ion-exchange chromatography using Q-Sepharose, heparin-Sepharose, Mono-Q and gel filtration with TSK G3000. The 120 kDa protein thus isolated was similar to human PK-120 with respect to limited proteolysis by kallikrein, amino acid composition, and the N-terminal amino acid sequence, indicating that the immunoreactive 120 kDa protein was guinea pig PK-120.