Interactions of kinins with angiotensin I converting enzyme (kininase II)

• Published in: Biochemical pharmacology Vol. 32; no. 24; p. 3839
• Main Authors: Odya, C E, Wilgis, F P, Vavrek, R J, Stewart, J M
• Format: Journal Article
• Language: English
• Published: England 15-12-1983
• Subjects: Animals; Kidney - enzymology; Kinins - metabolism; Peptidyl-Dipeptidase A - metabolism; Protein Binding; Rabbits; Receptors, Bradykinin; Receptors, Cell Surface - metabolism; Swine
• ISSN: 0006-2952
• DOI: 10.1016/0006-2952(83)90158-2

Angiotensin I converting enzyme (ACE) was purified to homogeneity from porcine kidney in order to determine whether iodobradykinins bind to the enzyme and, if so, whether pGlu-Trp-Pro-Arg-Pro-Gin-Ile-Pro-Pro, SQ20881, a competitive ACE inhibitor, changes the conformation of the enzyme in such a way that it binds kinins with an affinity and specificity expected of a bradykinin (BK) receptor, i.e. where the BK potentiating action of SQ20881 involves an increase in the number of BK receptors due to a conformational change in ACE. 125I-Labeled derivatives of [Tyr1]-kallidin and [Tyr-8]-bradykinin bound to the EDTA-inhibited enzyme, and binding was inhibited by nonradioactive BK. [125I-Tyr5]-BK was not bound by the enzyme. Specificity of [125I-Tyr5]-kallidin (T1K) binding was tested with forty-eight BK analogs, and the concentrations of analogs that inhibited 50% of T1K binding were determined. BK at 1.6 +/- 0.3 X 10(-8) M inhibited 505 of T1K binding. In addition, the concentrations of analogs that decreased by 50% the rate of [3H]-Hip-Gly-Gly ([3H]-HGG) hydrolysis by ACE were assessed. BK at 1.2 +/- 0.2 X 10(-6) M decreased the rate of [3H]-HGG hydrolysis by 50%. A comparison between these concentrations of analogs for inhibition of T1K binding and [3H]-HGG hydrolysis yielded a high correlation coefficient (r = 0.85). The specificity of ACE binding was clearly different from that expected of a BK receptor. Compounds structurally unrelated to BK, such as 5Q20881, pGlu-Lys-Trp-Ala-Pro-OH (BPP5a) and angiotensin I, inhibited T1K binding and [3H]-HGG hydrolysis by ACE.