The N domain of somatic angiotensin-converting enzyme negatively regulates ectodomain shedding and catalytic activity

The N domain of somatic angiotensin-converting enzyme negatively regulates ectodomain shedding and catalytic activity

Author Woodman, Zenda L. Google Scholar
Schwager, Sylva LU Google Scholar
Redelinghuys, Pierre Google Scholar
Carmona, Adriana Karaoglanovic Autor UNIFESP Google Scholar
Ehlers, Mario RW Google Scholar
Sturrock, Edward D. Google Scholar
Institution Univ Cape Town
Universidade Federal de São Paulo (UNIFESP)
Pacific Biometr Inc
Abstract sACE (somatic angiotensin-converting enzyme) consists of two homologous, N and C domains, whereas the testis isoenzyme [tACE (testis ACE)] consists of a single C domain. Both isoenzymes are shed from the cell surface by a sheddase activity, although sACE is shed much less efficiently than tACE. We hypothesize that the N domain of sACE plays a regulatory role, by occluding a recognition motif on the C domain required for ectodomain shedding and by influencing the catalytic efficiency. To test this, we constructed two mutants: CNdom-ACE and CCdom-ACE. CNdom-ACE was shed less efficiently than sACE, whereas CCdom-ACE was shed as efficiently as tACE. Notably, cleavage occurred both within the stalk and the interdomain bridge in both mutants, suggesting that a sheddase recognition motif resides within the C domain and is capable of directly cleaving at both positions. Analysis of the catalytic properties of the mutants and comparison with sACE and tACE revealed that the k(cat) for sACE and CNdom-ACE was less than or equal to the sum of the k(cat) values for tACE and the N-domain, suggesting negative cooperativity, whereas the k(cat) value for the CCdom-ACE suggested positive co-operativity between the two domains. Taken together, the results provide support for (i) the existence of a sheddase recognition motif in the C domain and (ii) molecular flexibility of the N and C domains in sACE, resulting in occlusion of the C-domain recognition motif by the N domain as well as close contact of the two domains during hydrolysis of peptide substrates.
Keywords angiotensin-converting enzyme
catalytic activity
domain selectivity
ectodomain shedding
proteolytic cleavage
Language English
Date 2005-08-01
Published in Biochemical Journal. London: Portland Press Ltd, v. 389, n. 3, p. 739-744, 2005.
ISSN 0264-6021 (Sherpa/Romeo, impact factor)
Publisher Portland Press Ltd
Extent 739-744
Access rights Open access Open Access
Type Article
Web of Science ID WOS:000231186400016

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