•The numbers of identified peptides were 250 in yogurt, 434 in gastric digest and 466 in pancreatic digest.•Gastric and pancreatic digests presented the better ACE and DPP-IV inhibition activity than yogurt.•κ-CN contributed the diversity of peptides in fermentation processing and β-CN did it in gastrointestinal digestion.This study investigated the relationship between peptide profiles and the bioactivity character of yogurt in simulated gastrointestinal trials. A total of 250, 434 and 466 peptides were identified by LC-MS/MS analyses of yogurt, gastric digest and pancreatic digest. Forty peptides of yogurt survived in gastrointestinal digestion. κ-CN and β-CN contributed the diversity of peptides during the fermentation process and gastrointestinal digestion, respectively. The favorite of κ-CN by lactic acid bacteria complemented gut digestion by hydrolyzing κ-CN, the low abundance milk proteins. The potential bioactivities were evaluated by in vitro ACE and DPP-IV inhibition assays. The ACE inhibition rate of the pancreatic digests was ~ 4 - and ~ 2 - fold greater than that of yogurt and the gastric digests. The ACE inhibitory peptides generated during gastrointestinal digestion improved the ACE inhibitory activity of the gastric and pancreatic digests. The DPP-IV inhibition rate of the pancreatic digest was ~ 6 - and ~ 3 - fold greater than that of yogurt and the gastric digest. The numbers of potential DPP-IV inhibitory peptides were positively correlated to the DPP-IV inhibitory activity of the gastric and pancreatic digests.Biological significanceThe present study describes the characters and bioactivities of peptides from yogurt in a simulated gastrointestinal digestion. The number of peptides identified from yogurt and gastrointestinal digests by LC-MS/MS increased in the simulated gastrointestinal trials. The in vitro ACE and DPP-IV inhibition bioactivities revealed that the bioactivity of yogurt was enhanced during gastrointestinal digestion. The correlation between peptides and bioactivity in vitro indicated that not only the peptides amount but also the proportion of peptides with high bioactivities contributed to increased bioactivity during gastrointestinal digestion. The study of peptides identified from yogurt and digests revealed that the number of released peptides was not determined by the abundance of the parent proteins but by whether the enzymes favored the protein.In summary, peptide profiling and bioactivities of yogurt in simulated gastrointestinal digestion helped to elucidate the health benefits of yogurt peptides. The results further revealed that pre-digestion of milk by lactic acid bacteria are complementary to generate bioactive peptides and to provide particular yogurt functions.

•We developed an integrated approach to screen DPP-IV inhibitory peptides.•5.9%~20.9% peptides of deer skin hydrolysates have a Pro at penultimate position.•Methionine oxidation and length of peptide affected their DPP-IV inhibitory activity.•The integrated approach is efficient to identify bioactive peptides.An integrated approach combining liquid chromatography/tandem mass spectrometry (LC–MS/MS) with in silico analysis was used to screen dipeptidyl peptidase IV (DPP-IV) inhibitory peptides from deer skin hydrolysates. A total of 203, 244 and 60 peptides were identified from deer skin hydrolysates prepared with pepsin, pepsin + trypsin and pepsin + Alcalase, respectively, by LC–MS/MS. The percentages of peptides in the above mentioned hydrolysates containing a Pro residue at the penultimate position were 5.9, 20.9 and 20.0%, respectively. Five peptides with a Pro residue at the penultimate position were synthesized and assessed, and these five synthetic peptides possessed DPP-IV inhibitory activity with IC50 values from 83.3 to 1638.3 µΜ. One of the evaluated peptides contained an oxidized methionine. The effects of peptide modification and length on the DPP-IV inhibitory activity of the peptides were assessed. The results suggest that the integrated approach was efficient in identifying novel bioactive peptides from hydrolysates.

•Protein digestomics of antler velvet was investigated by LC-MS/MS and bioactivity.•Antler velvet digests presented DPP-IV and PEP inhibitory activities.•The released bioactive peptides contributed to the bioactivity of antler velvet.Proteins are the most prominent bioactive component in deer antler velvet. The aim of the present study was to track the fate of protein of antler velvet by protein digestomics. The peptide profile identified by LC-MS/MS and the in vitro bioactivity of antler velvet aqueous extract (AAE) were investigated in simulated gastrointestinal digestion. A total of 23, 387 and 417 peptides in AAE, gastric and pancreatic digests were identified using LC-MS/MS, respectively. Collagens, the predominant proteins, released 34 peptides in gastric digests and 146 peptides in pancreatic digests. The gastric and pancreatic digests presented dipeptidyl peptidase IV (DPP-IV) and prolyl endopeptidase (PEP) inhibition activities. Four peptides from digests were proved to be DPP-IV and PEP inhibitory peptides. The results showed that the peptides released from antler velvet protein contributed to the bioactivity of antler velvet during digestion.Download high-res image (101KB)Download full-size image