Human psoriatic scale extracts produced kinins from heated plasma (11.3 +/- 5.5 ng kinin/mg protein) and from purified low molecular weight (LMW) bovine kininogen (4.4 +/- 1.7 ng/mg). Sephacryl S-200 gel filtration of the extracts showed three peaks of kininogenase activity with Mr values of 90,000 (K-I), 65,000 (K-II), and 35,000 (K-III). Upon DEAE-Sepharose chromatography of the Sephacryl peaks, K-I activity was found in the nonadsorbed fraction and formed kinins only from heated plasma. Peak K-II activity was resolved into two peaks, K-IIa (in the nonadsorbed fraction), which formed kinins only from heated plasma, and K-IIb (in the adsorbed fraction), which formed kinins from both heated plasma and LMW bovine kininogen. K-III kininogenase activity appeared at the same position as K-IIb and also formed kinins from both substrates. Kininogenases K-I and K-IIa had the same Km value (0.3 mM) with Pro-Phe-Arg-p-nitroanilide(pNA), similar to that found with human plasma kallikrein. The Km value of K-IIb with Val-Leu-Arg-pNA (0.8 mM) was like that found for human salivary kallikrein, whereas K-III had a low affinity for this substrate. Like plasma kallikrein, K-I and K-IIa were inhibited by soybean trypsin inhibitor, but only weakly by aprotinin. In addition the kininogenase activity of both K-I and K-IIa was neutralized by adding antihuman prekallikrein immunoglobulin G (IgG). In contrast, K-IIb and K-III were strongly inhibited by aprotinin but not by soybean trypsin inhibitor, consistent with their being tissue kallikreins. It was confirmed that K-IIb and K-III shares antigenic determinant of urinary kallikrein.