Differences in the properties and enzymatic specificities of the two active sites of angiotensin I-converting enzyme (kininase II). Studies with bradykinin and other natural peptides

E. Jaspard, L. Wei, F. Alhenc-Gelas

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278 Scopus citations


Angiotensin I-converting enzyme (ACE, E.C. has been recently shown to contain two very similar domains, each of which bears a functional active site hydrolyzing Hip-His-Leu or angiotensin I (AI). The substrate specificity of the two active sites of ACE was compared using wild-type recombinant ACE and mutants, where one active site is suppressed by deletion or inactivated by mutations of 2 histidines coordinating an essential zinc atom. Both active sites converted bradykinin (BK) to BK1-7 and BK1-5 with similar kinetics and with K(m)/(app) at least 30 times lower and k(cat)/K(m)/(app) 10 times higher than for AI. The carboxyl-terminal active site, but not the amino-terminal site, was activated by chloride; however, chloride activation was minimal compared with AI. Both domains also hydrolyzed substance P and cleaved a carboxyl-terminal protected dipeptide and tripeptide. The carboxyl-terminal active site was more readily activated by chloride and hydrolyzed substance P faster. Luteinizing-hormone releasing hormone was hydrolyzed by both active sites, but hydrolysis by the amino- terminal active site was faster. It performed the endoproteolytic amino- terminal cleavage of this peptide at least 30 times faster than the carboxyl- terminal active site. Both active sites cleaved a carboxyl-terminal tripeptide from luteinizing hormone-releasing hormone. Thus, both active sites of ACE possess dipeptidyl carboxypeptidase and endopeptidase activities. However, only the carboxyl-terminal active site can undergo a chloride-induced alteration that greatly enhances the hydrolysis of AI or substance P, and the amino-terminal active site possesses an unusual amino- terminal endoproteolytic specificity for a natural peptide. This suggests physiologically important differences between the subsites of the two active centers, and different substrate specificity, despite the high degree of sequence homology.

Original languageEnglish (US)
Pages (from-to)9496-9503
Number of pages8
JournalJournal of Biological Chemistry
Issue number13
StatePublished - Jan 1 1993


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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