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Purification of a Novel Angiotensin I-Converting Enzyme (ACE) Inhibitory Peptide with an Antihypertensive Effect from Loach (Misgurnus anguillicaudatus)

Li, Ying, Zhou, Jianzhong, Huang, Kaihong, Sun, Yi, Zeng, Xiaoxiong
Journal of agricultural and food chemistry 2012 v.60 no.5 pp. 1320-1325
Misgurnus anguillicaudatus, antihypertensive effect, enzyme inhibitors, high performance liquid chromatography, hydrolysates, inhibitory concentration 50, mass spectrometry, oral administration, papain, pepsin, peptidyl-dipeptidase A, rats, size exclusion chromatography, subtilisin, systolic blood pressure, ultrafiltration
To isolate and characterize novel angiotensin I-converting enzyme (ACE) inhibitory peptide from loach (Misgurnus anguillicaudatus), six proteases, pepsin, α-chymotrypsin, bromelain, papain, alcalase, and Neutrase, were used to hydrolyze loach protein. The hydrolysate (LPH) generated by bromelain [ratio of enzyme to substrate, 3:1000 (w/w)] was found to have the highest ACE inhibitory activity (IC₅₀, 613.2 ± 8.3 μg/mL). Therefore, it was treated by ultrafiltration to afford fraction of LPH-IV (MW < 2.5 kDa) with an IC₅₀ of 231.2 ± 3.8 μg/mL, having higher activity than the other fractions. Then, LPH-IV was isolated and purified by consecutive purification steps of gel filtration chromatography and reverse-phase high-performance liquid chromatography to afford a purified peptide with an IC₅₀ of 18.2 ± 0.9 μg/mL, an increase of 33.7-fold in ACE inhibitory activity as compared with that of LPH. The purified peptide was identified as Ala-His-Leu-Leu (452 Da) by Q-TOF mass spectrometry and amino acid analyzer. An antihypertensive effect in spontaneously hypertensive rats revealed that oral administration of LPH-IV could decrease systolic blood pressure significantly.