Peptide transporter information about function, role of the peptide transporter, applications of the peptide transporters.

1. PEPTIDE TRANSPORTER
1
Mr.Lingraj V. Sargar
M. Pharm,Sem-II
BHARATI VIDYAPEETH
College of Pharmacy, Kolhapur 1

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Contents
 Introduction
 Functions
 Peptide Transporter 1
 Role Of Peptide Transport
 Applications of PEPT 1
 Regulation of Peptide Transporter
 Location of peptide Transporter
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3. Introduction
 The basic mechanism is involved in solute transporter across the biological me
membrain include passive diffusion, facilited diffusion and, active transporter
 Active transporter can again divided in to primary and secondary active transp
ort.
 Peptides (mostly di-/tri-peptides) are normally crossed the BBB through peptid
e transporters found as an integral part of the plasma membrane proteins which
also mediate the trafficking of peptide-mimetic drugs
 It should be noted that the electrochemical Na+ gradient, so-called sodium-
motive force (SMF)
 The uptake and digestion of dietary proteins in the intestinal lumen are mainly
in the form of free amino acids and small peptides.
 These free amino acids and small peptides absorbed are delivered to various
tissues through the blood as resources for protein synthesis and energy metabol
ites
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4.  PepT1 was first identified in 1994 as a small peptide transporter.
 The complementary DNA (cDNA) encoding the human PepT1 is 2,263 base
pairs in length and has an open reading frame of 2,127 base pairs encoding 708
amino acids.
 155 Up until now, two peptide transporters, namely PepT1 (SLC15A1) and Pe
pT2 (SLC15A2), have been discovered in human, which are known as proton-
coupled transporters that influx oligopeptides of 2 to 4 AAs.
 Although their distributions vary from one organ to another, they are markedly
expressed by the epithelia of intestine and kidney
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5. Types of Transporters
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6. Functions
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1. SLC15A1is localized to the brush border membrane of the intestinal epithelium
and mediates the uptake of di- and tripeptides from the lumen into the
enterocytes.
2. This protein plays an important role in the uptake and digestion of dietary
proteins.
3. This protein also facilitates the absorption of numerous peptidomimetic drugs.
4. mediating critical physiologic functions – important for the cellular homeostasis
of peptides and AAs.
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7.  Peptide transporter 1 (PepT 1) also known as solute carrier family 15 member 1
(SLC15A1) is a protein that in humans is encoded by SLC15A1 gene. PepT 1 is a
solute carrier for oligopeptides. It functions in renal oligopeptide reabsorption and in
the intestines in a proton dependent way, hence acting like a cotransporter.
 This efflux transporter can be expressed in to gut improve drug absorption
Examples:-PEPT1,ASBT,OATP-B,OATP-D.And OATP-E.
 PEPT1 Mediate the transport like peptide-like drug such as β-lactum antibiotic,
ACEIs Inhibitors the dipeptide-like anticancer drug bestatin
Peptide Transporter 1
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The physiological characteristics of PepT1
 PepT1 is an electrogenic symporter that couples substrate and proton transport
across the cell membrane. The driving force for transport is an inwardly direct
ed -electrochemical gradient and membrane potential, which allow the substrat
es to accumulate to concentrations above the extracellular levels
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9.  Verri , Maffia , and Storelli (1992) measured accumulation in the presence of a
n inside-negative transmembrane potential in the intestinal brush-border memb
rane vesicles (BBMV) of the eel(Anguilla). Subsequently, in both herbivoro
us and carnivorous fish it was reported that intestinal transport of pep-tides is
gradient-dependent and electrogenic and sodium-independent.
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10. Fig:-Transport of small peptides across intestinal epithelial cells. In higher
eukaryotes, the PepT family diverged into PepT1 and has a prominent expression
in intestinal epithelial cells
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11. Molecular structure of PepT1 in fish
 Based on the 20 naturally occurring amino acids, there are more than 8000 pos
sible peptides expected to be transported by PepT1,therefore has a highly prom
iscuous binding site that can accommodate a wide range of ligands with divers
e structures and chemistries. The results from multiple studies have provided a
bundant evidence for the presence of PepT1 in fish, including in vivo studies (
Bogé et al., 1981, Dabrowski et al., 2003, Dabrowski et al., 2005), in vitro assa
ys (Reshkin & Ahearn, 1991) and molecular experiments (Gonçalves et al., 20
07).Bucking and Schulte demonstrated the first functional evidence that two is
oforms of PepT1 transporters were present in fish, named SLC15A1a and SLC
15A1b.
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12. 3-D modelling structure of Cyprinus carpio L PepT1. The structure was predicted using PyMOL .
The TM domains(transmembrane) and N- and C terminal regions are annotated.
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13. Role and location of PEPT1 and PEPT2 transporters
 PEPT1 and PEPT2 belong to the SLC transporter family and are the main pept
ide transporter within the body being responsible for the proton-coupled transp
ort of dipeptides and tripeptides. Their main function is in the absorption of di
etary nitrogen in the small intestine (PEPT1) and reabsorption of nitrogen fro
m the glomerular filtrate in the renal proximal tubule (both PEPT1 and PEPT
2).
 Pathogenesis of intestinal inflammation
 These transporters are also present in Brain and BBB
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14.  Firstly, localisation of PEPT1 is predominantly on the brush border of the smal
l intestine and to a lesser extent on renal epithelial cells whereas PEPT2 is wid
ely distributed in the body yet is mainly located in the renal epithelial cells.
 Secondly, PEPT1 is a low affinity, high capacity transporter whereas PEPT2 is
a high affinity, low capacity transporter. Although both transporters accept a la
rge number of substrates, PEPT2 is believed to have a narrower substrate rang
e than PEPT2.
 PEPT2 is widely distributed in the body and is expressed in the kidney, CNS,
and lung as well as several other tissues.
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15. Application of PEPT1 transporter in drug delivery
 PEPT1 is much more well characterised compared to PEPT2. This is in part du
e to the fact that uptake by PEPT1 is a popular route for prodrug design for dru
g delivery. For example, prodrugs which have amino acids as pro-moieties hav
e been designed as substrates of PEPT1 to improve oral absorption and bioavai
lability. The antivirals, valacyclovir and valganciclovir are examples where thi
s has been successful.
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16. Regulation of PEPT1 transporter and its role in intestinal
inflammation
 A number of factors have been reported to regulation of PEPT1 including alter
ed dietary intake and increased dietary protein. There is also evidence of the P
EPT1 transporter playing a role in the pathogenesis of intestinal inflammation
and inflammatory bowel disease. It is believed that the changes in expression o
f PEPT1 in the colon can lead to uptake of bacterial peptides. These peptides c
an activate pro-inflammatory signalling pathways leading to the release of cyto
kines and chemokines and ultimately an enhanced inflammatory response.
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17. Location of peptide Transporter
Peptide transporters localized at brush-border membranes of intestinal a
nd renal epithelial cells mediate the membrane transport of di- and tripeptides, and
play important roles in protein absorption and the conservation of peptide-bound a
mino nitrogen.
Peptide-like drugs that show structural similarities to di- and tripeptides
are also recognized by peptide transporters.
The energy for transport of small peptides and peptide-like drugs is provided by t
he proton gradient across the cell membrane.
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18. Membrane topology of peptide transporter 1 (PEPT1). (a) The protein contains 12 transmembr
ane domains, with the N-terminal and C-terminal ends in the cytosol. (b) Based on the analysi
s of chimeric transporters derived from PEPT1 and PEPT2, transmembrane domains in green f
orm part of the substrate-binding domain.
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19. Case Study :-The Transport of valganciclovir, a ganciclovir pr
odrug, via peptide transporters PEPT1 and PEPT2
In clinical trials, valganciclovir, the valyl ester of ganciclovir, has been s
hown to enhance the bioavailability of ganciclovir when taken orally by patients w
ith cytomegalovirus infection. We investigated the role of the intestinal peptide tra
nsporter PEPT1 in this process by comparing the interaction of ganciclovir and val
ganciclovir with the transporter in different experimental systems. We also studied
the interaction of these two compounds with the renal peptide transporter PEPT2. I
n cell culture model systems using Caco‐2 cells for PEPT1 and SKPT cells for PE
PT2, valganciclovir inhibited glycylsarcosine transport mediated by PEPT1 and P
EPT2 with Ki values (inhibition constant) of 1.68 ± 0.30 and 0.043 ± 0.005 mM,
respectively.
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20. The inhibition by valganciclovir was competitive in both cases. Gancicl
ovir did not interact with either transporter. Similar studies done with cloned PEP
T1 and PEPT2 in heterologous expression systems yielded comparable results. Th
e transport of valganciclovir via PEPT1 was investigated directly in PEPT1‐expres
sing Xenopus laevis oocytes with an electrophysiological approach. Valganciclovir
, but not ganciclovir, induced inward currents in PEPT1‐expressing oocytes. These
results demonstrate that the increased bioavailability of valganciclovir is related to
its recognition as a substrate by the intestinal peptide transporter PEPT1. This prod
rug is also recognized by the renal peptide transporter PEPT2 with high affinity.
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21. Types of Amino Acids
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22. Different parameters for Peptide calculation
Enter a peptide sequence using 1-letter or 3-letter amino acid codes and our peptid
e calculator will provide the following physio-chemical properties of the sequence
• Molecular weight
• Isoelectric Point
• Net charge at neutral pH(0.7)
• Average Hydrophilicity
• Ratio of hydrophilic residues to total number of residues
• Net charge Vs pH plot
• Hydrophobicity plot
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23. Software's
1. PyRx
2. KeyShot 8
3. Bachem
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24. Conclusion
OSR1 has the potency to downregulate the peptide transporters PEPT1 and PEPT2.
Further experiments are needed to define the in vivo significance of OSR1 sensitive p
eptide transport.
Normal human lung immunohistochemical analysis for PEPT2 protein revealed staini
ng of tracheal, bronchial, and smaller airway epithelial cells .The endothelium of smal
l vessels was also positive . The immunoreactivity was of a non-granular type and was
especially strong at the apical cellular membrane.
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25. Reference
1]Giacomini KM, Sugiyama Y. Brunton LL, Lazo JS, Parker RL. Gilman’s The Ph
armacological Basis of Therapeutics. 2006New YorkMcGraw-Hill:41–70. This ch
apter in a textbook provides an excellent overview of transporters. 2. Schinkel AH,
Jonker JW. Mammalian drug efflux transporters of the ATP binding cassette (ABC
) family: an overview. Adv. Drug Deliv. Rev. 2003; 55:3–29. [PubMed: 1253557
2] This manuscript provides an excellent review of ABC transporters that are impo
rtant in drug response.
3. Sai Y. Biochemical and molecular pharmacological aspects of transporters as d
eterminants of drug disposition. Drug Metab. Pharmacokinet. 2005; 20:91–99. [Pu
bMed: 15855719]
4. Cascorbi I. Role of pharmacogenetics of ATP-binding cassette transporters in th
e pharmacokinetics of drugs. Pharmacol. Ther. 2006; 112:457–473. [PubMed: 167
66035]
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26. 5. Choudhuri S, Klaassen CD. Structure, function, expression, genomic organizati
on, and single nucleotide polymorphisms of human ABCB1 (MDR1), ABCC (MR
P), and ABCG2 (BCRP) efflux transporters. Int. J. Toxicol. 2006; 25:231–259. [Pu
bMed: 16815813]
6. Hediger MA, et al. The ABCs of solute carriers: physiological, pathological an
d therapeutic implications of human membrane transport proteins. Pflugers Arch.
2004; 447:465–468. [PubMed: 14624363]
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