Phenotyping Angiotensin-Converting Enzyme in Blood: A Necessary Approach for Precision Medicine

Abstract

Background Angiotensin-converting enzyme (ACE) metabolizes a number of important peptides participating in blood pressure regulation and vascular remodeling. Elevated ACE expression in tissues (which is generally reflected by ACE in blood) is associated with increased risk of cardiovascular diseases. Elevated ACE in blood is also a marker for granulomatous diseases. Methods We applied our novel approach—ACE phenotyping—to characterize serum ACE in 300 unrelated patients and to establish normal values for ACE levels. ACE phenotyping includes (a) determination of ACE activity with 2 substrates (Z-Phe-His-Leu [ZPHL] and Hip-His-Leu [HHL]), (b) calculation of a ratio for hydrolysis of ZPHL and HHL, and (c) quantification of ACE immunoreactive protein levels and ACE conformation with a set of monoclonal antibodies (mAbs) to ACE. Results Only a combination of ACE activity determination with 2 substrates and quantification of the amount of ACE immunoreactive protein with mAbs 1G12 and 9B9 allows for the unequivocal detection of the presence of ACE inhibitors in the blood. After excluding such subjects, we were able to establish normal values of ACE in healthy populations: 50%–150% from control pooled serum. This ACE phenotyping approach in screening format with special attention to outliers can also identify patients with various mutations in ACE and may help to identify the as yet unknown ACE secretase or other mechanistic details of precise regulation of ACE expression. Conclusions ACE phenotyping is a promising new approach with potential clinical significance to advance precision medicine screening techniques by establishing different risk groups based on ACE phenotype.

Predictive potential of ACE phenotyping in extrapulmonary sarcoidosis

“…Our results revealed substantial inter-individual variability of ACE levels (activity and level of immunoreactive ACE protein) characterized by a threefold difference, i.e. indicating that ACE levels in this normal population can be characterized as 100 + 25% (variability from 50 to 150%) [ 36 ].…”

“…Previously we developed a new approach to characterize blood ACE in individual patients-blood ACE phenotyping [33][34][35][36]. This approach includes not just determination of ACE activity (with two substrates, ZPHL and HHL), but also determination of a novel kinetic parameter, the ratio of the rates of the hydrolysis of these two substrates (ZPHL/HHL ratio), which is able to control for the native state of the N and C domains of ACE active centers and to reveal the potentially complicating presence of ACE inhibitors [33][34][35][36]39].…”

“…Previously we developed a new approach to characterize blood ACE in individual patients-blood ACE phenotyping [33][34][35][36]. This approach includes not just determination of ACE activity (with two substrates, ZPHL and HHL), but also determination of a novel kinetic parameter, the ratio of the rates of the hydrolysis of these two substrates (ZPHL/HHL ratio), which is able to control for the native state of the N and C domains of ACE active centers and to reveal the potentially complicating presence of ACE inhibitors [33][34][35][36]39]. The third parameter is the concentration of ACE immunoreactive protein [19], and finally, the fourth and most sensitive approach is conformational fingerprinting of ACE using a set of anti-ACE mAbs showing subtle conformational changes in ACE surface topography [26,[33][34][35]42].…”

“…Therefore, elevated serum levels of ACE are more likely to reflect extrapulmonary sarcoidosis involvement. We have established a novel approach, blood ACE phenotyping, for the purpose of full characterization of ACE in plasma or serum [33][34][35][36].…”

Performance of Serum Angiotensin-Converting Enzyme in Diagnosing Sarcoidosis and Predicting the Active Status of Sarcoidosis: A Meta-Analysis

“…Firstly, the reason why is that the levels of ACE in plasma are stable in a given individual but vary greatly between subjects [ 65 ]. A normal range of ACE levels is one that varies three-fold in the tested population from the mean value, even up to 5.7 times among subjects [ 65 , 66 ]. The sACE levels that are within the normal range may actually be high in some people, which is related to the various polymorphisms of the ACE gene.…”