Table 3.
Representative ligand-mediated transport in oral delivery of therapeutic peptides/proteins.
| Name | Distribution/Function | Characteristics | Ref. |
|---|---|---|---|
| Bile acid transporters | In the epithelium of ileum | The ASBT in the small intestine transports bile acids into epithelial cells for bile acid recycling | 5., 48., 52., 76., 77., 78., 79., 80., 81. |
| UEA-1 | In M-cell | M-cell selective molecular signature | 20 |
| Lectin-like protein receptors | In the intestine | Proteins or glycoproteins specifically recognize the carbohydrate moieties on the intestine | 42 |
| Biotin (vitamin B7) receptor | In the intestine | The biotin receptor distributes throughout the small intestine | 55 |
| Proton-coupled oligopeptide transporters PepT1 and PepT2 | In the brush border membrane of the small intestine | Driven by the presence of an inward H+ gradient and a negative membrane potential. Transports various natural di/tri-peptides and comprehensive peptide-mimetics. High capacity, low affinity | 82., 83. |
| CSK peptide transporters | In goblet cells | CSK peptide specifically recognize goblet cells | 84 |
| AT-1002 peptide | Open TJs | A hexamer peptide derived from ZOT open the TJs transiently and reversibly | 85 |
| Monocarboxylate transporter | In the intestine | Cellular uptake of SCFAs efficiently, among which butyrate is in majority, a key mediator of physiological function in the intestine | 86 |
| CD44 receptor | In the intestine | A highly heterogeneous single-stranded transmembrane glycoprotein widely expressed on the membrane | 87 |
ASBT, apical sodium-dependent bile acid transporter; CSK, CSKSSDYQC; ZOT, zonula occludins toxin; TJs, tight junctions; UEA-1, ulex europaeus agglutinin-1; SCFAs, short chain fatty acids.