Angiotensin-Converting Enzyme-2 (ACE2):  Comparative Modeling of the Active Site, Specificity Requirements, and Chloride Dependence

Abstract

Angiotensin-converting enzyme 2 (ACE2), a homologue of ACE, represents a new and potentially important target in cardio-renal disease. A model of the active site of ACE2, based on the crystal structure of testicular ACE, has been developed and indicates that the catalytic mechanism of ACE2 resembles that of ACE. Structural differences exist between the active site of ACE (dipeptidyl carboxypeptidase) and ACE2 (carboxypeptidase) that are responsible for the differences in specificity. The main differences occur in the ligand-binding pockets, particularly at the S2' subsite and in the binding of the peptide carboxy-terminus. The model explains why the classical ACE inhibitor lisinopril is unable to bind to ACE2. On the basis of the ability of ACE2 to cleave a variety of biologically active peptides, a consensus sequence of Pro-X-Pro-hydrophobic/basic for the protease specificity of ACE2 has been defined that is supported by the ACE2 model. The dipeptide, Pro-Phe, completely inhibits ACE2 activity at 180 microM with angiotensin II as the substrate. As with ACE, the chloride dependence of ACE2 is substrate-specific such that the hydrolysis of angiotensin I and the synthetic peptide substrate, Mca-APK(Dnp), are activated in the presence of chloride ions, whereas the cleavage of angiotensin II is inhibited. The ACE2 model is also suggestive of a possible mechanism for chloride activation. The structural insights provided by these analyses for the differences in inhibition pattern and substrate specificity among ACE and its homologue ACE2 and for the chloride dependence of ACE/ACE2 activity are valuable in understanding the function and regulation of ACE2.

New Mass Spectrometric Assay for Angiotensin-Converting Enzyme 2 Activity

“…3,9 However, the ability of ACE2 to inactivate the vasoconstrictor Ang II and generate the putative cardioprotective metabolite Ang (1-7) implicates ACE2 as a potential regulator of the RAS. 3,9,23 Further clarification of the role of ACE2 in disease states will be assisted by the development of sensitive and rapid methods for measurement of ACE2 activity. There is also a need for miniaturized, reliable assays because of increasing use of mice as experimental models and the volume requirements of classical enzyme methods.…”

“…2 This step is followed by the action of angiotensin-converting enzyme (ACE, EC 3.4.15.1) 1, a peptidyl dipeptidase, which belongs to the gluzincin family of metalloproteases. 3 ACE1 cleaves the C-terminal dipeptide (L-histidyl-L-Leucine) of Ang I, generating the physiologically active vasoconstrictor peptide angiotensin II (Ang II). Ang II is the key mediator of the RAS, and its biological actions are produced through the selective binding of this peptide to 2 different types of receptors, Ang II type 1 and Ang II type 2.…”

“…19 A classical method for measurement of ACE2 tissue activity is based on the use of fluorogenic peptide substrates. 3,9,21,22 Another method that is accurate, but time consuming, is the use of radiolabeled peptide precursors followed by high-performance liquid chromatography (HPLC) separation of the peptide products. 23 Our recent studies have focused on the development of new proteolytic assay technologies.…”

Angiotensin-Converting Enzyme 2 (ACE2) and ACE Activities Display Tissue-Specific Sensitivity to Undernutrition-Programmed Hypertension in the Adult Rat

“…3 Like ACE, ACE2 is a zinc-dependent peptidase of the M2-metalloprotease family that is sensitive to chloride ion concentration. 4 ACE2 is a membrane-bound enzyme that acts as a monocarboxypeptidase and is an essential regulator of heart function. 5 However, ACE2 is not inhibited by the classical ACE inhibitors captopril and lisinopril, 1,6 which are used as antihypertensive drugs.…”

In vivo hypotensive effect and in vitro inhibitory activity of some Cyperaceae species

“…These data suggest that the proteolytic activity of ACE2 is different from the isoform ACE. Unlike ACE, ACE2 is the monopeptidilcarboxipeptidase (Guy et al, 2003;Warner et al, 2004;Guy et al, 2005).…”