Effect of molecular weight on the transepithelial transport and peptidase degradation of casein-derived peptides by using Caco-2 cell model

- We studied the effects of molecular weight on the transport routes of peptides.
- The brush-border peptidases are the limiting enzymes for peptide bioavailability.
- Peptides transported by PepT1 have higher bioavailability than peptides transported by paracellular route.
- Amino acid sequence of short chain peptides affects their bioavailability.

The transepithelial transport routes of casein-derived peptides with different molecular weights (MWs) were investigated using a Caco-2 cell monolayer. The peptidase hydrolysis during transport was also studied. The results indicate that the paracellular route was the main pathway for F1 (1600-1300 Da) and F2 (1000-500 Da), and the bioavailabilities were 10.66% and 9.54%, respectively. Peptidase hydrolysis results reveal that brush-border peptidases (BBPs) as well as some other peptidases were responsible for peptide degradation in the paracellular route. The maximum hydrolysis rate of the former was 6.91 and 5.59 μM Gly/min for the latter. However, PepT1 was involved in the transport of F3 (<500 Da) and its bioavailability was 16.23%. BBPs were the main peptidases involved in the PepT1 transport and the maximum hydrolysis rate was 11.4 μM Gly/min. Furthermore, we found that the amino acid sequence of di- and tripeptides might affect their bioavailabilities significantly.