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Biological Chemistry

Editor-in-Chief: Brüne, Bernhard

Editorial Board Member: Buchner, Johannes / Ludwig, Stephan / Sies, Helmut / Turk, Boris / Wittinghofer, Alfred

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The role of glycosylation and domain interactions in the thermal stability of human angiotensin-converting enzyme

Hester G. O'Neill1 / Pierre Redelinghuys2 / Sylva L.U. Schwager3 / Edward D. Sturrock4

1Division of Medical Biochemistry, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Observatory 7925, South Africa

2Division of Medical Biochemistry, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Observatory 7925, South Africa

3Division of Medical Biochemistry, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Observatory 7925, South Africa

4Division of Medical Biochemistry, Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Observatory 7925, South Africa

Corresponding author

Citation Information: Biological Chemistry. Volume 389, Issue 9, Pages 1153–1161, ISSN (Online) 1437-4315, ISSN (Print) 1431-6730, DOI: 10.1515/BC.2008.131, August 2008

Publication History

Received:
2007-12-20
Accepted:
2008-06-03
Published Online:
2008-08-19

Abstract

The N and C domains of somatic angiotensin-converting enzyme (sACE) differ in terms of their substrate specificity, inhibitor profiling, chloride dependency and thermal stability. The C domain is thermally less stable than sACE or the N domain. Since both domains are heavily glycosylated, the effect of glycosylation on their thermal stability was investigated by assessing their catalytic and physicochemical properties. Testis ACE (tACE) expressed in mammalian cells, mammalian cells in the presence of a glucosidase inhibitor and insect cells yielded proteins with altered catalytic and physicochemical properties, indicating that the more complex glycans confer greater thermal stabilization. Furthermore, a decrease in tACE and N-domain N-glycans using site-directed mutagenesis decreased their thermal stability, suggesting that certain N-glycans have an important effect on the protein's thermodynamic properties. Evaluation of the thermal stability of sACE domain swopover and domain duplication mutants, together with sACE expressed in insect cells, showed that the C domain contained in sACE is less dependent on glycosylation for thermal stabilization than a single C domain, indicating that stabilizing interactions between the two domains contribute to the thermal stability of sACE and are decreased in a C-domain-duplicating mutant.

Keywords: angiotensin-converting enzyme; co-operativity; melting temperature; N-linked glycosylation; thermal stability

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