![]() PEPT1 and PEPT2 translocate dipeptides and tripeptides produced by protein catabolism. More recently, two new type 1 (PHT1, SLC15A4) and type 2 (PHT2, SLC15A3) peptide/histidine transporters have been identified in mammals. Peptide transporters 1 and 2 (PEPT1 and PEPT2, SLC15A1 and SLC15A2, respectively) are H +-coupled oligopeptide symporters ( Figure 3) whose predicted membrane topology anticipates the 12 TMDs of the SLC family ( Figure 6). Scherrmann, in Comprehensive Medicinal Chemistry II, 2007 5.04.4.2.4 PEPT1 ( SLC15A1) and PEPT2 ( SLC15A2) transporters Overall, any manipulation of peptide transporters is likely to interfere with peptide absorption and to have gastrointestinal consequences, which may limit the utility of this approach in metabolic disease. PEPT1 is expressed in the apical membrane of acutely isolated murine intestinal CCK-positive endocrine cells, but its release in this model is only stimulated by protein hydrolysates but not PEPT1 specific peptides ( Liou et al., 2011a). ![]() Increased levels of PEPT1 protein have been reported to up-regulate the absorption of glycine-glutamine in Caco-2 cells after additional insulin treatment ( Thamotharan et al., 1999). Pept1 knockout mice fed a high protein diet have increased arginine and decreased leptin levels in plasma, and show significantly reduced food intake in first few days ( Nässl et al., 2011). This increased absorption is lost in Pept1 knockout mice ( Ma et al., 2012). Under fasted conditions, rats show an increased oral absorption of glycine-sarcosine and correspondingly increased PEPT1 protein was detected in fasted mouse small intestine. It has been further reported that PEPT1 on L cells plays an important role in glycine-sarcosine oligopeptide and proton-stimulated GLP-1 secretion ( Diakogiannaki et al., 2013). PEPT1 is highly expressed in L cells in the small intestine and colon of mice ( Diakogiannaki et al., 2013). Similarly, the in vitro intestinal uptake and in vivo oral absorption of dipeptides are both reduced in mice with disrupted Pept1 expression in intestine and kidney ( Hu et al., 2008). Dipeptide absorption is found absent in cells isolated from Pept2 knockout mouse colon tissues ( Rühl et al., 2005). The absorption of intestinal fluids and dipeptide uptake from the small intestinal lumen via PEPT1 relies on a negative apical membrane potential ( Chen et al., 2010). They are also found in other tissues in rodents, for example, PEPT2 is expressed in kidney and brain ( Lu and Klaassen, 2006). Both transporters are highly expressed in the gastrointestinal tract, where they are found in enterocytes and EECs, and in neurons of the myenteric plexus in the mouse intestine ( Groneberg et al., 2001 Rühl et al., 2005). PEPT1 is a low-affinity and high-capacity transporter, while PEPT2 is a high-affinity and low-capacity transporter ( Rubio-Aliaga and Daniel, 2008). Peptide transporter 1 and 2 (PEPT1 and PEPT2) mediate the absorption and the transportation of dipeptides and tripeptides in the intestinal epithelium ( Daniel and Kottra, 2004). Murphy, in Reference Module in Biomedical Sciences, 2021 1.2.1.7 PEPT1 and PEPT2 peptide transporter
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