[Kininase from the Latrodectus tredecimguttatus venom. Characteristics of the enzyme as a thiol endopeptidase hydrolyzing the -Pro7-Phe8- bond of bradykinin].

The nature of the bradykinin (BK)-hydrolyzing (kininase) activity of peptidhydrolase isolated from spider (Latr. tredecimguttatus) venom has been studied. It was found that the BKase activity of the enzyme is fully inhibited by organic mercurials (10(-5)-10(-6) M) as well as by 5,5'-dithiobis(2-nitrobenzoic acid) (10(-7) M); the latter blocks three SH-groups within the enzyme molecule. Serine and metalloproteinase inhibitors have no effect on the kininase activity. Thin-layer chromatography on silicagel revealed that the highly purified enzyme hydrolyzes the -Pro7-Phe8- bond of BK liberating the C-terminal dipeptide, HPhe-ArgOH. Besides, the kininase splits off the C-terminal tripeptide from angiotensin I by hydrolyzing its -Pro7-Phe8-bond. The enzyme does not exhibit any exopeptidase activity with free and N-substituted tri- and pentapeptides. The data obtained suggest that the Latr. tredecimguttatus kininase can be related to thiol endopeptidases hydrolyzing the peptide bonds formed by proline carboxyl.