Enzymatic Investigations of Partially Purified Hog Kallikrein

KALLIKREIN, discovered by Frey in 1925 1 , was observed to be a hypotensive agent. Later work by many investigators has led to the present hypothesis that kallikrein is an enzyme, formed from a precursor kallikreininoken, which acts on protein substrates to liberate the biologically active polypeptides, substance P , kallidin II, and bradykinin. It is these substances which manifest the hypotensive activity 2,3 . Because trypsin possesses the same ability to release active polypeptides, it becomes important for future investigations to differentiate clearly the two enzymes, trypsin and kallikrein.