Studies on the kinin formation by bovine spleen acid kininogenases

The modes of action of acid kininogenase I and II on bovine kininogens were investigated. The pH profile of kinin forming reaction from bradykininogen for each enzyme proved the fact that these enzymes react preferably at acidic condition. Acid kininogenase I produced kinin presumably from nicked HMW kininogen which has bradykinin moiety at the C-terminal, but not from intact HMW or LMW kininogens. Acid kininogenase II could react on any kind of kininogen tested. The peptides produced were purified and subjected to molecular weight determination and also to sequence analysis. Estimated molecular weights were 1,300 and 1,400 for the peptides produced by AK I and 1,900 for the one produced by AK II. N-terminal amino acids were revealed to be methionine, leucine and arginine, respectively.