Self carbohydrate-mediated dimerization of glycoprotein angiotensin-converting enzyme (ACE) was demonstrated. The dimerization was studied in the reverse micelle experimental system as a model of biomembrane situation. Asialo-ACE or agalacto-ACE was able to form a dimer, whereas deglycosylated ACE and sequentially desialylated and degalactosylated ACE failed to dimerize. ACE-ACE interaction was competitively inhibited by Neu5Ac- or Gal-terminated saccharides. The results have allowed us to propose the existence of carbohydrate-recognizing domain (CRD) on ACE molecule. The structural requirements of this CRD were estimated based on the ability of saccharides to inhibit ACE dimerization. The most effective monosaccharides with equal inhibition potencies were shown to be galactose (as GalbetaOMe) and N-acetylneuraminic acid (as Neu5AcalphaOMe). Among oligosaccharides, the most effective ones were found to be 3'SiaLac and, especially, the whole pool of ACE oligosaccharide chains and biantennae complex oligosaccharide chains of other glycoproteins. Bovine and human ACEs were shown to be similar in terms of recognition of carbohydrates.

Self carbohydrate‐mediated dimerization of glycoprotein angiotensin‐converting enzyme (ACE) was demonstrated. The dimerization was studied in the reverse micelle experimental system as a model of biomembrane situation. Asialo‐ACE or agalacto‐ACE was able to form a dimer, whereas deglycosylated ACE and sequentially desialylated and degalactosylated ACE failed to dimerize. ACE–ACE interaction was competitively inhibited by Neu5Ac‐ or Gal‐terminated saccharides. The results have allowed us to propose the existence of carbohydrate‐recognizing domain (CRD) on ACE molecule. The structural requirements of this CRD were estimated based on the ability of saccharides to inhibit ACE dimerization. The most effective monosaccharides with equal inhibition potencies were shown to be galactose (as GalβOMe) and N‐acetylneuraminic acid (as Neu5AcαOMe). Among oligosaccharides, the most effective ones were found to be 3′SiaLac and, especially, the whole pool of ACE oligosaccharide chains and biantennae complex oligosaccharide chains of other glycoproteins. Bovine and human ACEs were shown to be similar in terms of recognition of carbohydrates. Copyright © 2000 John Wiley & Sons, Ltd.

To study the role of the oligosaccharide moiety in the catalytic properties of angiotensin-converting enzyme (ACE), we obtained asialo-and partially deglycosylated ACE by enzymatic treatment of two-domain somatic enzyme from bovine lung. Treated enzymes demonstrated appreciable, but different changes of catalytic properties in the reaction of the hydrolysis of N-substituted tripeptides, C-terminal analogs of angiotensin I and bradykinin among them, compared to those for native enzyme. Deglycosylation also altered the catalytic properties of a single N domain of bovine ACE. So, various patterns of glycosylation modulate substrate specificity of somatic ACE and may be the reason for functional heterogeneity of the enzyme.z 1998 Federation of European Biochemical Societies.