Isolation of kallikrein from mammary gland of cows.

Small amounts of kallikrein were isolated from bovine mammary tissue. Immediately after slaughter, the udder was removed, perfused with ice-cold xylocaine-Rheomacrodex solution, and homogenized in ice-cold acetic acid solution. Kallikrein-like substances were adsorbed on DEAE-cellulose, eluted with ammonium formate and fractionated by acetone precipitation. The 40-70% acetone fraction was separated on a Shephadex-G 75 column and aliquots of each fraction were incubated for 1 or 2 hr with kininogen. After incubation, extracts were tested for kinin activity on the isolated rat uterus, the rat duodenum, blood flow through the femoral artery of dogs and by intramammary pressure assay in sheep. Release of kinins was demonstrated by all these techniques, highest kallikrein activity being detected in the molecular weight range 50,000 to 60,000. Direct injection of the enzyme into the udder artery of sheep, without prior incubation with kinninogen, resulted in vasodilation and a rise in intramammary pressure. The kallikrein activity was strongly inhibited by aprotinin, but not by soybean trypsin inhibitor or ovomucoid. Kallikrein activity was always associated with esterase activity.