Isolation and identification of peptidic alpha-glucosidase inhibitors derived from sardine muscle hydrolyzate.

We report here the isolation of alpha-glucosidase (AGH) inhibitory peptides derived from sardine muscle hydrolyzate, which was prepared by digestion with Bacillus licheniformis alkaline protease. As a result of reversed-phase HPLC purification, two AGH inhibitory peptides were isolated from a DEAE-Sephadex A-25 column eluate. The peptides were identified as follows: Val-Trp (IC50 = 22.6 mM) and Try-Tyr-Pro-Leu (IC50 = 3.7 mM). AGH inhibitory studies of Try-Tyr-Pro-Leu and its derivatives demonstrated the importance of the tri-peptide chain length as well as the hydrophobic aromatic amino acid tyrosine at the N-terminus, aliphatic amino acids at the C-terminus, as well as an amide proton from the peptide chain at the middle position of the tri-peptide to develop AGH inhibition activity.