BROMELAIN, A THIOLPROTEASE FROM PINEAPPLE STEM, DEPLETES HIGH MOLECULAR-WEIGHT KININOGEN BY ACTIVATION OF HAGEMAN-FACTOR (FACTOR-XII)

Intravenous injection of bromelain into rats produced marked hypotension, the second injection showing tachyphylaxis. These phenomena may be caused by activation of the plasma kallikrein-kinin system, followed by exhaustion of high molecular weight (HMW) kininogen. Plasma prekallikrein and HMW kininogen, but not low molecular weight kininogen, were markedly reduced 15 min after the injection of bromelain and gradually reappeared in 72 hrs. The site of action of bromelain in the kallikrein-kinin system was investigated by in vitro experiments which showed that normal human and rat plasma generated prekallikrein activator activity (active factor XII) as well as kinin after 10 min incubation with bromelain whereas Hageman factor deficient plasma did not. These results suggest that bromelain activates plasma prekallikrein by activation of factor XII. © 1979.