Activation of the Kallikrein-Kinin System in Human Plasma by a Serine Protease from Mites

A serine protease was earlier purified to homogeneity from a culture extract of mites and its possible involvement in the allergic reaction was proposed [K. Takahashi et al. (1990): Int. Arch. Allergy Appl. Immun., 91, 80-85]. The serine protease thus obtained was found in the present study to be trypsin-like protease and had high substrate specificity towards the synthetic substrate for blood coagulation factor XIIa. The enzyme gave rise to rhythmic contraction of rat uterine horns in factor XII-deficient human plasma, but not in prekallikrein-deficient plasma. These findings lead us to conclude that this enzyme activates the kallikrein-kinin system in plasma through hydrolysis of prekallikrein in the plasma.