QIGLF, a novel angiotensin I-converting enzyme-inhibitory peptide from egg white protein

BACKGROUND: Novel angiotensin I-converting enzyme (ACE)-inhibitory peptides from egg white protein can be rapidly screened by liquid chromatography/tandem mass spectrometry (LC/MS/MS). In this study, several peptides with higher ACE-inhibitory activity were prepared from egg white protein by enzymatic hydrolysis with Alcalase, purified with Sephadex G25, identified by LC/MS/MS and their structure determined by circular dichroism (CD) spectroscopy. RESULTS: Peptide sequences DHPFLF, HAEIN and QIGLF that showed ACE-inhibitory activity were investigated further for their stability in gastrointestinal solution and for changes in their secondary structure in solution mixtures. QIGLF exhibited the highest activity (IC50 = 75 mu mol L-1) and was resistant to digestion by proteases of the gastrointestinal tract. The CD spectrum of QIGLF showed the presence of the a-helix conformation. CONCLUSION: Three peptides were identified by LC/MS/MS and synthesised by Fmoc solid phase synthesis. Of the three, only the peptide sequence QIGLF was a potential ACE inhibitor, with an IC50 value of 75 mu mol L-1. Moreover, QIGLF showed low gastrointestinal enzyme susceptibility and contained a relatively high amount of a-helix. (C) 2011 Society of Chemical Industry