Different in vivo functions of the two catalytic domains of angiotensin-converting enzyme (ACE) (original) (raw)
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Journal of Biological Chemistry, 2004
Angiotensin-converting enzyme (ACE) produces the vasoconstrictor angiotensin II. The ACE protein is composed of two homologous domains, each binding zinc and each independently catalytic. To assess the physiologic significance of the two ACE catalytic domains, we used gene targeting in mice to introduce two point mutations (H395K and H399K) that selectively inactivated the ACE N-terminal catalytic site. This modification does not affect C-terminal enzymatic activity or ACE protein expression. In addition, the testis ACE isozyme is not affected by the mutations. Analysis of homozygous mutant mice (termed ACE 7/7) showed normal plasma levels of angiotensin II but an elevation of plasma and urine N-acetyl-Ser-Asp-Lys-Pro, a peptide suggested to inhibit bone marrow maturation. Despite this, ACE 7/7 mice had blood pressure, renal function, and hematocrit that were indistinguishable from wild-type mice. We also studied compound heterozygous mice in which one ACE allele was null (no ACE expression) and the second allele encoded the mutations selectively inactivating the N-terminal catalytic domain. These mice produced approximately half the normal levels of ACE, with the ACE protein lacking N-terminal catalytic activity. Despite this, the mice have a phenotype indistinguishable from wild-type animals. This study shows that, in vivo, the presence of the C-terminal ACE catalytic domain is sufficient to maintain a functional renin-angiotensin system. It also strongly suggests that the anemia present in ACE null mice is not due to the accumulation of the peptide N-acetyl-Ser-Asp-Lys-Pro.
Hypertension, 1998
We used the isolated N-and C-domains of the angiotensin I-converting enzyme (N-ACE and C-ACE; ACE; kininase II) to investigate the hydrolysis of the active 1-7 derivative of angiotensin (Ang) II and inhibition by 5-S-5-benzamido-4-oxo-6-phenylhexanoyl-L-proline (keto-ACE). Ang-(1-7) is both a substrate and an inhibitor; it is cleaved by N-ACE at approximately one half the rate of bradykinin but negligibly by C-ACE. It inhibits C-ACE, however, at an order of magnitude lower concentration than N-ACE; the IC 50 of C-ACE with 100 mol/L Ang I substrate was 1.2 mol/L and the K i was 0.13. While searching for a specific inhibitor of a single active site of ACE, we found that keto-ACE inhibited bradykinin and Ang I hydrolysis by C-ACE in approximately a 38-to 47-times lower concentration than by N-ACE; IC 50 values with C-ACE were 0.5 and 0.04 mol/L. Furthermore, we investigated how Ang-(1-7) acts via bradykinin and the involvement of its B 2 receptor. Ang-(1-7) was ineffective directly on the human bradykinin B 2 receptor transfected and expressed in Chinese hamster ovary cells. However, Ang-(1-7) potentiated arachidonic acid release by an ACE-resistant bradykinin analogue (1 mol/L), acting on the B 2 receptor when the cells were cotransfected with cDNAs of both B 2 receptor and ACE and the proteins were expressed on the plasma membrane of Chinese hamster ovary cells. Thus like other ACE inhibitors, Ang-(1-7) can potentiate the actions of a ligand of the B 2 receptor indirectly by binding to the active site of ACE and independent of blocking ligand hydrolysis. This potentiation of kinins at the receptor level can explain some of the well-documented kininlike actions of Ang-(1-7). (Hypertension. 1998;31:912-917.)
Circulation Research, 2003
Somatic angiotensin-converting enzyme (ACE) contains two homologous domains, each bearing a functional active site. The in vivo contribution of each active site to the release of angiotensin II (Ang II) and the inactivation of bradykinin (BK) is still unknown. To gain insights into the functional roles of these two active sites, the in vitro and in vivo effects of compounds able to selectively inhibit only one active site of ACE were determined, using radiolabeled Ang I or BK, as physiological substrates of ACE. In vitro studies indicated that a full inhibition of the Ang I and BK cleavage requires a blockade of the two ACE active sites. In contrast, in vivo experiments in mice demonstrated that the selective inhibition of either the N-domain or the C-domain of ACE by these inhibitors prevents the conversion of Ang I to Ang II, while BK protection requires the inhibition of the two ACE active sites. Thus, in vivo, the cleavage of Ang I and BK by ACE appears to obey to different mechanisms. Remarkably, in vivo the conversion of Ang I seems to involve the two active sites of ACE, free of inhibitor. Based on these findings, it might be suggested that the gene duplication of ACE in vertebrates may represent a means for regulating the cleavage of Ang I differently from that of BK.
2014
Angiotensin converting enzyme is an ectoprotein prone to regulated proteolytic solubilisation by an as yet unknown protease or sheddase. Proteolytic cleavage of membrane proteins is an essential cellular process that controls their expression and function, and modulates cellular and physiological processes. Testis ACE (tACE) is shed at a higher rate than somatic ACE and it has been proposed that regions in its ectodomain direct its shedding. Discrete secondary structures on the surface of the distal ectodomain of tACE were replaced with their N-domain counterparts to determine their role in the ectodomain shedding of ACE. None of the regions investigated proved to be an absolute requirement for shedding, but the mutant ACE proteins were subject to variations in shedding compared to wild-type tACE. To investigate the role of the proximal ectodomain in shedding the residues H 610-L 614 were mutated to alanines, causing a decrease in shedding. An extension of this mutation on the N-terminal side to seven alanines resulted in a reduction in ACE activity and, more importantly, it affected the processing of the protein to the membrane, resulting in expression of an underglycosylated form of ACE. When E 608-H 614 was mutated to the homologous region of the N-domain, processing was normal and shedding only marginally reduced. These data suggest that this region is more crucial for the processing of ACE than is for regulating shedding. Construction of a P 628 L mutation in tACE showed an increase in shedding. Furthermore, MALDI analysis of a tryptic digest established that the putative glycosylation site N 620 WT became glycosylated. Further mutagenesis of the P 628 L mutant to remove the newly formed glycosylation site, resulted in an even greater increase in shedding. Soluble fluorogenic peptides mimicking the ACE stalk were used in a cell-based assay to characterise the contribution of the stalk to ACE shedding. Hydrolysis of the wild-type peptide Abz-NSARSEGPQ-EDDnp was not responsive to phorbol ester or the hydroxamate inhibitor (TAPI), however, it was inhibited by EDTA. The aminopeptidase inhibitor bestatin did not inhibit cleavage or alter the cleavage site. Therefore the protease involved in the ABSTRACT iii cleavage of the ACE stalk peptides is likely different to the sheddase responsible for ACE shedding. Substitution of the P1 and P1' sites of the peptides did not significantly influence the rate of cleavage. All the peptides were cleaved at the E-G bond, which is C-terminal to the physiological R-S cleavage site. Removal of the fluorogenic capping groups resulted in no cleavage of the peptides and lengthening of the peptide did not result in cleavage. This ABBREVIATIONS 3D three-dimensional Å angstrom Abz ortho-aminobenzoic acid ACE angiotensin-converting enzyme ACE2 angiotensin-converting enzyme 2 ACN acetonitrile Ac-SDKP acetyl-SDKP ADAM a distintergrin and metalloprotease ADAMTS-13 a distintergrin and metalloprotease with a thrombospondin type 1 motif ALCAM activated leukocyte cell adhesion molecule AMPS ammonium persulphate AngI angiotensin I AngII angiotensin II APP amyloid precursor protein ATR1 angiotensin II receptor type 1 ATR2 angiotensin II receptor type 2 Aβ a yloid β peptide 1-42 B2 bradykinin 2 receptor BiP immunoglobulin binding protein BK bradykinin bp base pair BSA bovine serum albumin CaM calmodulin CC-ACE ACE with two C-domains CHO-K1 Chinese hamster ovary CK2 casein kinase CN-ACE ACE with C-domain at N-terminus and N-domain at C-terminus CO 2 carbon dioxide COS 7 African green monkey fibroblast-like kidney cells CRD carbohydrate recognition domain Cys cysteine
Rediscovering ACE: novel insights into the many roles of the angiotensin-converting enzyme
Journal of Molecular Medicine, 2013
Angiotensin converting enzyme (ACE) is best known for the catalytic conversion of angiotensin I to angiotensin II. However, the use of gene-targeting techniques has led to mouse models highlighting many other biochemical properties and actions of this enzyme. This review discusses recent studies examining the functional significance of ACE tissue-specific expression and the presence in ACE of two independent catalytic sites with distinct substrates and biological effects. It is these features which explain why ACE makes important contributions to many different physiological processes including renal development, blood pressure control, inflammation and immunity.
FEBS Journal, 2005
Angiotensin-converting enzyme-2 (ACE2) is a membrane protein with its active site exposed to the extracellular surface of endothelial cells, the renal tubular epithelium and also the epithelia of the lung and the small intestine . Here ACE2 is poised to metabolize circulating peptides which may include angiotensin II, a potent vasoconstrictor and the product of angiotensin I cleavage by angiotensin-converting enzyme (ACE; EC 3.4.15.1) . Indeed, ACE2 has been implicated in the regulation of heart and renal function where it is proposed to control the concentrations of angiotensin II relative to its hypotensive metabolite, angiotensin-(1-7) . Most recently, ACE2 has been identified as a functional receptor for the coronavirus which causes the severe acute respiratory syndrome (SARS) . For recent reviews, see .
Biochemistry, 2002
Somatic angiotensin I converting enzyme (ACE) contains two functional active sites. Up to now, most of the studies aimed at characterizing the selectivity of inhibitors toward the two ACE active sites relied on the use of ACE mutants containing a single functional active site. By developing new fluorogenic synthetic substrates of ACE, we demonstrated that inhibitor selectivity can be assessed directly by using somatic ACE. This useful screening approach led us to discover that some bradykinin potentiating peptides turned out to be selective inhibitors of the C-domain of ACE. The peptide pGlu-Gly-Leu-Pro-Pro-Arg-Pro-Lys-Ile-Pro-Pro, with K i (app) values of 30 nM and 8 µM, respectively, for the C-and N-domain of ACE, is to our knowledge the most highly selective C-domain inhibitor of ACE so far reported. Inhibitors able to block selectively either the Nor C-domain of ACE will represent unique tools to probe the function of each domain in the regulation of blood pressure or other physiopathological events involving ACE activity.