A STUDY OF CHIMERAS CONSTRUCTED WITH THE 2 DOMAINS OF ANGIOTENSIN I-CONVERTING ENZYME

Angiotensin I-converting enzyme (ACE) is composed of two highly simila r domains called the N and C domains, which display some contrasting e nzymatic properties. We constructed two ACE chimeras: chimera 1, compr ised of the N domain containing the central 60 amino acid residues of the C domain, and chimera 2, comprised of the C domain containing the central 60 amino acid residues of the N domain. Chimeras 1 and 2 displ ayed K-m values for Hip-His-Leu and 2-Phe-His-Leu and k(cat) ratios fo r these two substrates similar to that of the N and C domains, respect ively. Thus, the short sequence exchanged between the two domains does not confer the specific properties of that domain for these two subst rates but, rather, such specific properties must arise from the sequen ces surrounding the central region in each domain.