Detection of an angiotensin converting enzyme inhibitory peptide from peanut protein isolate and peanut polypeptides by western blot and dot blot hybridization

摘要

The peptide P7, with an amino acid sequence of Cys-Val-Thr-Pro-Ala-Leu-Arg, inhibits angiotensin I-converting enzyme (ACE). In this paper, P7 was identified in peanut protein isolate (PPI) and peanut polypeptides (PPs) with a new method. The P7 peptide was synthesized and used in the preparation of an antiserum. Using the antiserum, P7 was specifically identified in PPI by western blot, and its level in PPI and PPs was assayed by dot blot hybridization. The results showed that two bands of P7 expression with molecular weight 18–25 and 25–35 kDa were seen in PPI by glucan gel chromatography. The positive reaction rate of P7 in PPs was higher than in PPI, consistent with the measured ACE inhibitory activity. The rate of P7 in sample no. 3 reached 39.29% of the positive control, using a dose of 20 μg/mL. This sample had an ACE inhibitory activity of 89.73%. Therefore, western blot and dot blot hybridization with prepared antibody against synthetic peptide was a very sensitive detection method for peptide.