Targeted liberation and fractionation of angiotensin-I converting enzyme (ACE)-inhibitory tripeptides from wheat gluten

Research output: ThesisMaster's thesis


The literature review deals with ACE and ACE-inhibitory peptides, and their inhibition mechanism. The possibility of obtaining ACE-inhibitory peptides from food sources, especially wheat gluten, was discussed. In vitro ACE-inhibition activity measurement using substrate furanacryloyl-prolyl-glycyl-glycine (FAPGG) was introduced.

The aim of the experimental work was to degrade substrate wheat gluten by enzymatic hydrolysis of thermolysin and prolyl endoprotease from Aspergillus niger (AN-PEP, Clarex). The hydrolysis characteristics were determined by SDS-PAGE, free amino nitrogen content, and size-exclusion chromatography. Following ultrafiltration, the in vitro ACE-inhibition activity of hydrolysate was measured, and expressed by IC50 value. Two steps of reverse phase liquid chromatography (RPLC) were applied to purify hydrolysates and coupled with mass spectrometry (MS), targeted tripeptides were identified.

The optimum condition for thermolysin hydrolysis of wheat gluten was pH 8.0, at 40 ˚C for 4 hours incubation, and for Clarex hydrolysis was pH 4.0, at 70 ˚C for 22 hours. The sample hydrolysed by thermolysin first and then, by Clarex contained 126.6 mg/l free amino nitrogen, and main molecular distribution was under 6.5 kDa. After 3 kDa cut-off ultrafiltration, first thermolysin then Clarex treated hydrolysate showed strongest ACE-inhibition activity, IC50 value 0.016 mg protein/ml. RPLC fractionation was carried out by a C18 column; fractions were collected and further separated by a C8 column. According to an external standard, ACE-inhibitory tripeptide Leu-Gln-Pro was identified. Targeted liberation of ACE-inhibitory peptides appears a promising approach to produce blood pressure lowering peptides from wheat gluten.
Original languageEnglish
Publication statusPublished - Nov 2011
MoE publication typeG2 Master's thesis, polytechnic Master's thesis

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