Related Experiment Video
Updated: May 8, 2026

Peptide and Protein Quantification Using Automated Immuno-MALDI (iMALDI)
Published on: August 18, 2017
Comparison of analytical methods to assay inhibitors of angiotensin I-converting enzyme
Jiwang Chen1, Yimei Wang, Ran Ye
1College of Food Science and Engineering, Wuhan Polytechnic University, Wuhan, 430023 Hubei, China. jiwangchen1970@126.com
Abstract:
The linearity, precision and repeatability of visible spectrophotometric (VSP) and high-performance liquid chromatography (HPLC) methods for analysis of inhibitory activity of angiotensin I-converting enzyme (ACE) were compared by using several inhibitors and Hip-His-Leu (HHL) as substrates. IC50 values (concentration at which ACE activity is inhibited by 50%) of 0.00206±0.00005 μg/mL for captopril, 192±4.53 μg/mL for soybean peptides, and 153±4.29 μg/mL for grass carp peptides determined by the VSP method, and these values were 1.07, 1.07, 1.18 and 1.44-fold, respectively, higher than those from the HPLC method. In addition, the inhibitory constant (Ki value) of captopril was determined to be 7.09 nM and 4.94 nM using VSP and HPLC method, respectively. These results showed that the HPLC method revealed a higher level of sensitivity and precision, suitable for assaying ACE inhibition activity of antihyper-sensitive peptides. In contrast, the VSP method can simultaneously measure several samples with simple operations, suitable for analysis of ACE inhibition activity of food protein enzymatic hydrolysates.
Related Concept Videos
Antihypertensive Drugs: Angiotensin-Converting Enzyme Inhibitors
Antihypertensive Drugs: Direct Renin Inhibitors
Heart Failure Drugs: Inhibitors of Renin-Angiotensin System
Enzyme-Linked Immunosorbent Assay
There are many different types of ELISAs, but they all involve an antibody molecule whose constant region binds an enzyme, leaving the variable region free to bind its specific antigen. Enzyme-substrate reaction allows the antigen to be visualized or quantified.
Antihypertensive Drugs: Angiotensin II Receptor Blockers
Enzyme Inhibition

