Substrate specificities of acid kininogenases.
Two kinin forming enzymes were extracted from bovine spleen and separated from cathepsin B1 and B2 by DEAE-Cellulose chromatography. Since these catheptic kininogenases were found to release kinins from kininogens at acidic pH's, these were named acid kininogenase I and II. The presence of SH compounds was not necessary for I to have a kinin forming activity, while it was necessary for II. These have only minor difference for electrophoretic behaviors as can be seen, e.g., from a small difference in pI values, but could be separated by polyacrylamide gel electrophoresis. Their production of kinins from bovine crude bradykininogen was highly reproducible. Kininogenase I was proved to react on bovine HMW kininogen and also to release some kinin from LMW kininogen and leukokininogen. From the study of several substrates, these enzymes were revealed to have very low tryptic and little esterolytic activities and to have affinity to some hydrophobic amino acids.