title: Direct spectrophotometric measurement of angiotensin I-converting enzyme inhibitory activity for screening bioactive peptides.
abstract: A direct, extraction-free spectrophotometric assay was developed for determination of angiotensin I-converting enzyme activity (ACE) in the presence of ACE inhibitors using hippuryl-l-histidyl-l-leucine (HHL) as the ACE-specific substrate. This method relies on previously published spectrophotometric determination of hippuric acid (HA) content in the urine, the method of which was based on the specific colorimetric reaction of HA with benzene sulfonyl chloride (BSC) in the presence of quinoline. The proposed ACE inhibition assay was applied to the measurement of the ACE inhibitory activity of Captopril. IC(50) value of Captopril corresponded well with literature data. Furthermore, Alcalase hydrolysates of mung bean and rice protein isolates were assessed for ACE inhibitory activity by this method. These two hydrolysates showed high ACE inhibitory activity. This method proposed here was shown to be direct, sensitive, accurate, reproducible, and less expensive without separation of HA from ACE reaction mixture, and can be used for the screening of ACE inhibitory peptides derived from food proteins.
authors.affiliation: School of Food Science and Technology, Southern Yangtze University, 170 Huihe Road, Wuxi, Jiangsu 214036, PR China.
authors.forename: Guan-Hong
authors.initials: GH
authors.lastname: Li
authors.forename: Huan
authors.initials: H
authors.lastname: Liu
authors.forename: Yong-Hui
authors.initials: YH
authors.lastname: Shi
authors.forename: Guo-Wei
authors.initials: GW
authors.lastname: Le
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D002138:Calibration; D007887:Fabaceae / Q000737:chemistry; D006626:Hippurates / Q000737:chemistry; D006868:Hydrolysis; D020128:Inhibitory Concentration 50; D012275:Oryza / Q000737:chemistry; D010455:Peptides / Q000302:isolation & purification / Q000494:pharmacology*; D007703:Peptidyl-Dipeptidase A / Q000737:chemistry / Q000378:metabolism*; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013053:Spectrophotometry
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D006626:Hippurates; D010455:Peptides; D007703:Peptidyl-Dipeptidase A; C030514:hippuric acid