| Summary: | A low molecular weight (< 1 kDa) hydrolysate of Atlantic salmon protein has previously been shown to have anti-diabetic effects in vitro and in mouse models. This salmon peptide fraction (SPF) produced using the enzymes pepsin, trypsin and chymotrypsin, contains hundreds of potential bioactive compounds and the identification the functional modulators of this activity may realize novel therapeutic compounds or targets as treatments for type 2 diabetes. The aim of this study was therefore to identify the sequences and characteristics of potential bioactive peptides from the SPF with a functional effect in cultured L6 myotubes. Separation of progenitor proteins by electrophoresis and of SPF by column chromatography with gel filtration and strong anion exchange formats were successful at concentrating bioactive peptides into multiple subfractions. Tandem mass spectrometry of subfractions suggested that di- and tripeptides composed of Ile/Leu, Val, Asp, Glu, Trp, Tyr were common among peptides identified in bioactive fractions. The importance of functional peptide concentration and sequence motifs on bioactivity was tested using the synthetic sequences Ile-Ala-Tyr and Ile-Gly-Tyr and exhibited a stimulating effect at 2.8 nM, but an inhibiting effect at 2.8 pM. Swiss Target Prediction suggested these sequences are peptidomimetics of agonists to mu-type, delta-type and kappa-type opioid receptors. When considering the large total number of peptides and abundance of sequences containing similar motifs in SPF, its bioactivity is likely the result of complex interactions of many peptides.
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