β‐amino acid substitution to investigate the recognition of angiotensin II (AngII) by angiotensin converting enzyme 2 (ACE2)

In spite of the important role of angiotensin converting enzyme 2 (ACE2) in the cardiovascular system, little is known about the substrate structural requirements of the AngII–ACE2 interaction. Here we investigate how changes in angiotensin II (AngII) structure affect binding and cleavage by ACE2. A series of C3 β-amino acid AngII analogs were generated and their secondary structure, ACE2 inhibition, and proteolytic stability assessed by circular dichroism (CD), quenched fluorescence substrate (QFS) assay, and LC-MS analysis, respectively. The β-amino acid-substituted AngII analogs showed differences in secondary structure, ACE2 binding and proteolytic stability. In particular, three different subsets of structure-activity profiles were observed corresponding to substitutions in the N-terminus, the central region and the C-terminal region of AngII. The results show that β-substitution can dramatically alter the structure of AngII and changes in structure correlated with ACE2 inhibition and/or substrate cleavage. β-amino acid substitution in the N-terminal region of AngII caused little change in structure or substrate cleavage, while substitution in the central region of AngII lead to increased β-turn structure and enhanced substrate cleavage. β-amino acid substitution in the C-terminal region significantly diminished both secondary structure and proteolytic processing by ACE2. The β-AngII analogs with enhanced or decreased proteolytic stability have potential application for therapeutic intervention in cardiovascular disease. Copyright © 2010 John Wiley & Sons, Ltd.