title: Metabolism of bradykinin agonists and antagonists by plasma aminopeptidase P.
abstract: In addition to angiotensin I converting enzyme (ACE; EC 3.4.15.1) and carboxypeptidase N (CPN; EC 3.4.17.3), other peptidases contribute to bradykinin (BK) degradation in plasma. Rat plasma degraded BK by hydrolysis of the N-terminal Arg1-Pro2 bond, and the characteristics of hydrolysis are consistent with identification of aminopeptidase P (APP; EC 3.4.11.9) as the responsible enzyme. BK and BK[1-5] N-terminal hydrolysis was optimal at neutral pH, was inhibited by 2-mercaptoethanol, dithiothreitol, o-phenanthroline and EDTA, but was unaffected by the aminopeptidase inhibitors amastatin, puromycin and diprotin A, the endopeptidase-24.11 inhibitors phosphoramidon and ZINCOV, and the ACE and CPN inhibitors captopril and D,L-mercapto-methyl-3-guanidinoethylthiopropanoic acid (MERGETPA), respectively. Although kallidin (Lys-BK) was not metabolized directly by APP, conversion to BK by plasma aminopeptidase M (EC 3.4.11.2) resulted in subsequent degradation by APP. BK analogs containing N-terminal Arg1-Pro2 bonds, including [Tyr8-(OMe)] BK and [Phe8 psi(CH2NH)Arg9]BK (B2 agonists), des-Arg9-BK and [D-Phe8]des-Arg9-BK (B1 agonists), and [Leu8]des-Arg9-BK (B1 antagonist), were degraded by APP with Km and Vmax values comparable to those found for BK (Km = 19.7 +/- 2.6 microM; Vmax = 12.1 +/- 1.2 nmol/min/mL). In contrast, B2 antagonists containing D-Arg0 N-termini, including D-Arg[Hyp3,Thi5.8,D-Phe7]BK and D-Arg[Hyp3,D-Phe7,Phe8 psi(CH2NH)Arg9]BK, were resistant to APP-mediated hydrolysis. These data support a role for plasma aminopeptidase P in the degradation of circulating kinins, and a variety of B2 and B1 kinin agonists and antagonists. However, APP does not participate in the degradation of D-Arg0-containing antagonists.
authors.affiliation: Department of Physiology, Ohio State University, Columbus 43210.
authors.forename: P E
authors.initials: PE
authors.lastname: Ward
authors.forename: A
authors.initials: A
authors.lastname: Chow
authors.forename: G
authors.initials: G
authors.lastname: Drapeau
mesh_terms: D015097:3-Mercaptopropionic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000626:Aminopeptidases / Q000097:blood*; D000818:Animals; D001920:Bradykinin / Q000037:antagonists & inhibitors / Q000097:blood* / Q000502:physiology; D002216:Captopril / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007609:Kallidin / Q000097:blood; D007700:Kinetics; D007705:Kinins / Q000097:blood*; D001121:Lysine Carboxypeptidase / Q000037:antagonists & inhibitors / Q000097:blood; D007703:Peptidyl-Dipeptidase A / Q000097:blood; D051381:Rats
chemical_list: D007705:Kinins; D007609:Kallidin; C029729:2-mercaptomethyl-3-guanidinoethylthiopropionic acid; D002216:Captopril; D015097:3-Mercaptopropionic Acid; D000626:Aminopeptidases; C022750:X-Pro aminopeptidase; D007703:Peptidyl-Dipeptidase A; D001121:Lysine Carboxypeptidase; D001920:Bradykinin