Isolation and characterisation of a novel angiotensin I-converting enzyme-inhibitory peptide derived from douchi, a traditional Chinese fermented soybean food

摘要

BACKGROUND: Douchi, a traditional fermented soybean food, has recently attracted a great deal of attention owing to its superior physiological activity. In the present study the angiotensin I-converting enzyme (ACE)-inhibitory activity of typical douchi procured from various regions of China was analysed. An ACE-inhibitory peptide derived from the most potent douchi was also isolated and characterised. The pattern of ACE inhibition and resistance to hydrolysis by gastrointestinal proteases of this peptide are described.RESULTS: ACE-inhibitory activities were detected in all douchi samples, with IC values ranging from 0.204 to 2.011 mg mLp#. Among the douchi samples, a Mucor-type douchi exhibited the most potent ACE-inhibitory activity (IC = 0.204 mg mLp#). A novel ACE-inhibitory peptide was then isolated from this Mucor-type douchi using ultrafiltration followed by Sephadex G-25 column chromatography and reverse phase high-performance liquid chromatography. The amino acid sequence of the purified peptide was identified by Edman degradation as His-Leu-Pro (IC = 2.37 omol Lp#). The peptide is a competitive inhibitor and maintained its inhibitory activity even after incubation with some gastrointestinal proteases.CONCLUSION: The present study shows that peptides derived from soybean fermentation during douchi processing could be the main contributor to the ACE-inhibitory activity observed. Copyright