Báo cáo khoa học: The bioactive dipeptide anserine is transported by human proton-coupled peptide transporters doc

The bioactive dipeptide anserine is transported by human
proton-coupled peptide transporters
Stefanie Geissler
1
, Madlen Zwarg
1
, Ilka Knu
¨
tter
1
, Fritz Markwardt
2
and Matthias Brandsch
1
1 Membrane Transport Group, Biozentrum of Martin-Luther-University Halle-Wittenberg, Halle, Germany
2 Julius-Bernstein-Institute for Physiology, Martin-Luther-University Halle-Wittenberg, Halle, Germany
Introduction
The bioactive dipeptide anserine (b-alanyl-1-N-methyl-
l-histidine) is found in considerable amounts in skele-
tal muscle and brain of vertebrates [1,2]. It is formed
as a secondary product through the methylation of the
dipeptide carnosine (b-alanyl-l-histidine) [3]. The reac-
tion is catalysed by carnosine N-methyltransferase
[3,4]. Both anserine and carnosine exert antioxidative
properties, pH buffering capacity and transglycating
activity [5,6]. Anserine and carnosine are thought to
inhibit lipid oxidation by a combination of free radical
scavenging and metal chelation [7]. Furthermore,
anserine and carnosine enhance postdenervation
depolarization by the inhibition of NO production [8].
Because of the many recent reports on the endoge-

nous biochemical effects of anserine on the one
hand, and its presence in human diet on the other, the
intestinal absorption of anserine has received increas-
ing interest recently. In 2009, the intestinal absorption
of anserine after the ingestion of an anserine-contain-
ing diet, and its blood clearance, were studied [2].
Ingested anserine is absorbed intact into human blood
and is then hydrolysed to p-methyl-l-histidine and
Keywords
carnosine; intestine; kidney; PEPT1; PEPT2
Correspondence
M. Brandsch, Membrane Transport Group,
Biozentrum of Martin-Luther-University
Halle-Wittenberg, Weinbergweg 22,
D-06120 Halle, Germany
Fax: +49 345 5527258
Tel: +49 345 5521630
E-mail: matthias.brandsch@biozentrum.
uni-halle.de
(Received 4 November 2009, revised 2
December 2009, accepted 2 December
2009)
doi:10.1111/j.1742-4658.2009.07528.x
The bioactive dipeptide derivative anserine (b-alanyl-1-N-methyl-l-histidine)
is absorbed from the human diet in intact form at the intestinal epithelium.
The purpose of this study was to investigate whether anserine is a substrate
of the H
+
⁄ peptide cotransporters 1 and 2 (PEPT1 and PEPT2). We first
assessed the effects of anserine on [

14
C]glycylsarcosine ([
14
C]Gly-Sar) uptake
into Caco-2 cells expressing human PEPT1 and into spontaneous hyperten-
sive rat kidney proximal tubule (SKPT) cells expressing rat PEPT2. Anser-
ine inhibited [
14
C]Gly-Sar uptake with K
i
values of 1.55 mm (Caco-2) and
0.033 mm (SKPT). In HeLa cells transfected with pcDNA3-hPEPT1 or
pcDNA3-hPEPT2, K
i
values of 0.65 mm (hPEPT1) and 0.18 mm (hPEPT2)
were obtained. We conclude from these data that anserine is recognized by
PEPT1 and PEPT2. Carnosine also inhibited [
14
C]Gly-Sar uptake. Using
the two-electrode, voltage-clamp technique at Xenopus laevis oocytes, strong
hPEPT1-specific inward transport currents were recorded for Gly-Sar,
anserine and carnosine, but not for glycine. We conclude that anserine and
carnosine interact with the human intestinal peptide transporter and are
transported by hPEPT1 in an active, electrogenic H
+
symport. As PEPT1
is the predominant transport system for di- and tripeptides at the intestinal
epithelium, this transporter is most probably responsible for the intestinal
absorption of anserine after food intake. In addition, anserine might be
useful for the design of new substrates of peptide transporters, such as

prodrugs, that can be administered orally.
Abbreviations
Gly-Sar, glycylsarcosine; hPEPT, human PEPT; PEPT1, H
+
⁄ peptide cotransporter 1; PEPT2, H
+
⁄ peptide cotransporter 2; rPEPT, rat PEPT;
SKPT, spontaneous hypertensive rat kidney proximal tubule.
790 FEBS Journal 277 (2010) 790–795 ª 2010 The Authors Journal compilation ª 2010 FEBS
b-alanine by serum and tissue carnosinases. According
to the authors, this was the first study to demonstrate
the intestinal absorption of anserine [2]. It should be
noted, however, that, as early as 1976, Hama et al. [9]
concluded from their studies on the absorption of
b-alanine, anserine and carnosine that physiological
amounts of anserine (and carnosine) are absorbed
from rat small intestine in intact form. Very recently,
Yeum et al. [10] have investigated the metabolic stabil-
ity of carnosine and anserine in human serum and
their absorption kinetics in vivo. Again, the anserine
concentration was increased significantly after diges-
tion of anserine-rich food. The molecular mechanism
of anserine uptake remains unknown. Based on the in
vivo data and molecular structure of anserine, we
hypothesized that anserine might be recognized by the
intestinal peptide transporter. At the intestinal epithe-
lium, di- and tripeptides are transported from the
lumen into the enterocytes by H
+
⁄ peptide cotransport-

er 1 (PEPT1) (peptide transporter 1) (for a review, see
[11,12]). At the renal epithelium, small peptides are
reabsorbed from the glomerular filtrate into the cells
by the subtypes PEPT1 and PEPT2. PEPT2 is also
expressed in other tissues, such as lung and choroid
plexus. In addition to peptides, both PEPT1 and
PEPT2 also accept several pharmacologically relevant
peptidomimetics as substrates, such as many b-lactam
antibiotics, valacyclovir and d-aminolaevulinic acid
[12]. The intestinal proton-coupled peptide transport
system also accepts carnosine as substrate [13,14] (for
a review, see [15]). To the best of our knowledge, the
transport of anserine by H
+
⁄ peptide cotransporters
has not yet been studied. Interaction with these carri-
ers would not only deliver new information on the
substrate specificity of the transporters, but transport
by PEPT1 would also explain the high oral availability
of anserine.
Results and discussion
Inhibition of [
14
C]glycylsarcosine ([
14
C]Gly-Sar)
uptake at Caco-2 and spontaneous hypertensive
rat kidney proximal tubule (SKPT) cells by
anserine
Caco-2 and SKPT cell cultures are well-established

systems for intestinal and renal peptide transport studies.
Caco-2 cells express the human low-affinity, high-
capacity (‘intestinal’)-type peptide transport system
PEPT1, whereas SKPT cells express the rat high-affinity,
low-capacity (‘renal’)-type system PEPT2, but not
PEPT1 [16–18]. In the present investigation, we first
determined the effect of anserine on [
14
C]Gly-Sar uptake.
Gly-Sar is used as reference substrate for peptide
transport studies because of its relatively high enzymatic
stability. At concentrations of 10 mm (Caco-2) and 2 mm
(SKPT), anserine strongly inhibits the uptake of
[
14
C]Gly-Sar (10 lm) by 76% and 79%, respectively.
With both cell lines, competition assays at increasing
concentrations of Gly-Sar and anserine were performed.
From the inhibition curves shown in Fig. 1, IC
50
values,
i.e. the inhibitor concentration necessary to inhibit
carrier-mediated [
14
C]Gly-Sar uptake by 50%, were
calculated and converted into K
i
values, as described
previously [16–19]. Gly-Sar, a prototype substrate
for PEPT1 and PEPT2, displayed K

i
values of
0.74 ± 0.01 mm and 0.11 ± 0.01 mm, respectively
(Fig. 1, Table 1). Anserine inhibited [
14
C]Gly-Sar uptake
mediated by PEPT1 into Caco-2 cells with a K
i
value
of 1.55 ± 0.02 mm. The K
i
value of anserine for the
inhibition of [
14
C]Gly-Sar uptake via PEPT2 into SKPT
cells was 0.033 ± 0.001 mm (Table 1).
The apparent affinity of anserine is thereby lower
than that of Gly-Sar at PEPT1, but higher at PEPT2.
As reviewed earlier, most dipeptides composed of
natural amino acids display K
i
values in the range
0.07–0.7 mm at PEPT1 and 5–100 lm at PEPT2
[11,12]. According to our classification [12], anserine
can be considered as a medium-affinity ligand for
human PEPT1 and a high-affinity ligand for rat
PEPT2.
Effect of anserine on [
14
C]Gly-Sar uptake in

HeLa-hPEPT1 and HeLa-hPEPT2 cells
Caco-2 and SKPT cells originate from different
species, man and rat, respectively. To rule out the pos-
Fig. 1. Inhibition of [
14
C]Gly-Sar uptake into Caco-2 and SKPT cells
by anserine. Uptake of 10 l
M [
14
C]Gly-Sar was measured for
10 min at pH 6.0 in the presence of increasing concentrations of
anserine (n = 3–4).
S. Geissler et al. Anserine transport by peptide transporters
FEBS Journal 277 (2010) 790–795 ª 2010 The Authors Journal compilation ª 2010 FEBS 791
sibility that differences in substrate recognition
between hPEPT1 and rPEPT2 reflect species’ differ-
ences and to confirm the affinity constants obtained in
Caco-2 and SKPT cells in a second, independent
approach, we performed transport studies with cloned
human PEPT1 and PEPT2 [17]. The interaction of
anserine and, for comparison, carnosine and Gly-Sar
with hPEPT1 and hPEPT2 was studied in competition
assays after heterologous expression of the transporters
in HeLa cells (Fig. 2). For anserine, K
i
values of
0.65 ± 0.02 mm and 0.18 ± 0.01 mm were determined
at hPEPT1 and hPEPT2, respectively (Table 1).
Carnosine inhibited [
14

C]Gly-Sar uptake with K
i
values
of 1.7 ± 0.1 mm (hPEPT1) and 0.06 ± 0.01 mm
(hPEPT2). Unlabelled Gly-Sar inhibited [
14
C]Gly-Sar
uptake with K
i
values of 0.64 ± 0.02 mm (hPEPT1)
and 0.24 ± 0.02 mm (hPEPT2). These results clearly
show that anserine interacts specifically with hPEPT1
and hPEPT2 and that the compound inhibits the
uptake of the prototype substrate Gly-Sar.
Transport of anserine by hPEPT1 expressed in
Xenopus laevis oocytes
Inhibition of [
14
C]Gly-Sar uptake at native intestinal or
renal cells, or at transfected cells expressing peptide
transporters heterologously, does not allow the conclu-
sion to be drawn that the inhibiting, competing com-
pound – in this case anserine – is indeed transported.
Anserine could represent an inhibitor blocking directly
the binding site of the carrier. Alternatively, the results
obtained so far do not rule out an indirect effect, for
example an effect on the proton gradient, as the driving
force of [
14
C]Gly-Sar uptake. Employing the two-

electrode, voltage-clamp technique, we therefore inves-
tigated whether anserine is able to generate currents at
X. laevis oocytes expressing hPEPT1. These currents
occur when a compound is cotransported by PEPT1
with H
+
in an electrogenic manner. As shown in
Fig. 3, anserine (10 mm) generated inward currents
(1254 ± 44 nA) comparable with those generated by
Table 1. Inhibition constants (K
i
) of Gly-Sar, anserine and carnosine at PEPT1 and PEPT2. Uptake of [
14
C]Gly-Sar in Caco-2 and SKPT cells,
or in HeLa cells transfected with hPEPT1- or hPEPT2-cDNA, was measured at pH 6.0 for 10 min at increasing concentrations of unlabelled
dipeptides. K
i
values were derived from the competition curves shown in Figs 1 and 2 (n = 4). ND, not determined.
K
i
(mM)
Compound
hPEPT1
Caco-2
rPEPT2
SKPT
hPEPT1
HeLa
hPEPT2
HeLa

Gly-Sar 0.74 ± 0.01 0.11 ± 0.01 0.64 ± 0.02 0.24 ± 0.02
Anserine 1.55 ± 0.02 0.033 ± 0.001 0.65 ± 0.02 0.18 ± 0.01
Carnosine ND ND 1.7 ± 0.1 0.06 ± 0.01
Fig. 2. Inhibition of [
14
C]Gly-Sar uptake into HeLa cells transfected
with pcDNA3-hPEPT1 and pcDNA3-hPEPT2 constructs by anserine,
carnosine and Gly-Sar. Uptake of 20 l
M [
14
C]Gly-Sar was measured
for 10 min at pH 6.0 in the presence of increasing concentrations
of the compounds for the determination of IC
50
values (n = 3–4).
10 mM Anserine
10 m
M Carnosine
10 m
M Gly-Sar
20 m
M Glycine
500 nA
10 sec
Fig. 3. Electrophysiological analysis of anserine transport in
hPEPT1-cRNA-injected X. laevis oocytes (membrane potential,
)60 mV; pH 6.5). Lower trace: currents induced by 10 m
M anser-
ine, carnosine and Gly-Sar, and 20 m
M glycine. Upper trace: mea-

surement in water-injected oocytes.
Anserine transport by peptide transporters S. Geissler et al.
792 FEBS Journal 277 (2010) 790–795 ª 2010 The Authors Journal compilation ª 2010 FEBS
the prototype transporter substrate Gly-Sar
(1220 ± 42 nA) and by the structurally related sub-
strate carnosine (1075 ± 24 nA). No currents were
observed for either of the test compounds in water-
injected oocytes (Fig. 3). Hence, indirect PEPT1-
independent effects of anserine can be ruled out.
PEPT1 does not accept free amino acids as substrates.
Therefore, glycine was used as negative control in these
experiments. No inward currents could be observed
(Fig. 3).
We conclude from these data that anserine is recog-
nized by the proton-coupled peptide transporters
PEPT1 and PEPT2 with medium affinity. Anserine is
able to displace other substrates from the transport
process. The experiments show that anserine and car-
nosine are transported by hPEPT1 in an active, elec-
trogenic manner by an H
+
symport. As PEPT1 is the
predominant transport system for di- and tripeptides
at the intestinal epithelium, this transporter is most
probably responsible for the intestinal absorption of
anserine after food intake. After entering the blood
compartments and tissues, the hydrolysis of anserine –
which is relatively resistant against intestinal dipeptid-
ases – occurs in serum caused by the activity of carno-
sinases [10,20,21].

With regard to the structural requirements for
PEPT1 and PEPT2 substrates, it is surprising that
anserine, with its N-terminal b-amino acid, displays
such high affinity. Therefore, in addition to the physio-
logical and biochemical aspects of anserine transport,
this compound might also be useful for the design of
new substrates of peptide transporters, such as pro-
drugs, that can be administered orally.
Experimental procedures
Materials
Caco-2 and HeLa cells were obtained from the German
Collection of Microorganisms and Cell Cultures (Braun-
schweig, Germany). The renal cell line SKPT-0193 Cl.2,
established from isolated cells of rat proximal tubules, was
provided by U. Hopfer (Case Western Reserve University,
Cleveland, OH, USA) [16]. Cell culture media, supplements
and trypsin solution were purchased from Life Technolo-
gies, Inc. (Karlsruhe, Germany) or PAA (Pasching,
Austria). Fetal bovine serum was obtained from Biochrom
(Berlin, Germany). [Glycine-1-
14
C]Gly-Sar (specific radioac-
tivity, 56 mCiÆmmol
)1
) was custom synthesized by GE
Healthcare (Little Chalfont, Buckinghamshire, UK). Anser-
ine was purchased from Bachem (Weil am Rhein, Ger-
many), and Gly-Sar and carnosine from Sigma-Aldrich
(Deisenhofen, Germany).
Culture of Caco-2 and SKPT cells

Caco-2 cells were routinely cultured in 75 cm
2
culture flasks
with minimum essential medium supplemented with 10%
fetal bovine serum, gentamicin (50 lgÆmL
)1
) and 1% nones-
sential amino acid solution [16–18]. Subconfluent cultures
(80% of confluence) were treated for 5 min with Dulbecco’s
phosphate-buffered saline, followed by a 2 min incubation
with trypsin solution. For uptake experiments, cells were
seeded in 35 mm disposable Petri dishes (Sarstedt, Nu
¨
mbr-
echt, Germany) at a density of 0.8 · 10
6
cells per dish. The
monolayers reached confluence the next day. The uptake
measurements were performed on the seventh day after seed-
ing. The protein content per dish was determined using a
Pierce
Ò
660 nm Protein Assay (Thermo Fisher Scientific,
Bonn, Germany) according to the manufacturer’s protocol.
The culture medium for SKPT cells was Dulbecco’s
modified Eagle’s medium ⁄ F12 nutrient mixture (1 : 1, v ⁄ v)
supplemented with fetal bovine serum (10%), gentamicin
(50 lgÆmL
)1
), epidermal growth factor (10 ngÆmL

)1
),
insulin (4 lgÆmL
)1
), dexamethasone (5 lgÆmL
)1
) and apo-
transferrin (5 lgÆmL
)1
). SKPT cells were seeded in Petri
dishes at a density of 0.8 · 10
6
cells per dish. The uptake
measurements were performed on the fourth day after
seeding [16–18].
Heterologous expression of human PEPT1 and
human PEPT2 in HeLa cells
HeLa cells were routinely cultured with Dulbecco’s modi-
fied Eagle’s medium with Glutamax, supplemented with
10% fetal bovine serum and gentamicin (50 lgÆmL
)1
). The
cDNA of human PEPT1 and PEPT2 was cloned into
pcDNA3 using the pBluescript constructs as a template for
PCR, and XhoI and BamHI as restriction sites [17]. The
resulting pcDNA3-hPEPT1 ⁄ 2 constructs were confirmed by
sequencing. Human PEPT1 and human PEPT2 were heter-
ologously expressed in HeLa cells using pcDNA3-hPEPT1
or pcDNA3-hPEPT2 constructs (1 lg per well) and Turbo-
fect (1.5 lL per well; Fermentas, St. Leon-Rot, Germany),

according to the manufacturer’s protocol. Transfection was
performed 1 h postseeding in 24-well plates [17].
[
14
C]Gly-Sar uptake measurements
The uptake of [
14
C]Gly-Sar (10 lm) in Caco-2 and SKPT
cells cultured on plastic dishes was measured at room tem-
perature, as described previously [16–18]. The uptake buffer
was 25 mm Mes ⁄ Tris (pH 6.0) containing 140 mm NaCl,
5.4 mm KCl, 1.8 mm CaCl
2
, 0.8 mm MgSO
4
,5mm glucose,
[
14
C]Gly-Sar (10 lm) and unlabelled Gly-Sar, anserine or
carnosine (0–10 mm, pH readjusted if necessary). After
incubation for 10 min, the monolayers were quickly washed
four times with ice-cold uptake buffer, solubilized and pre-
S. Geissler et al. Anserine transport by peptide transporters
FEBS Journal 277 (2010) 790–795 ª 2010 The Authors Journal compilation ª 2010 FEBS 793
pared for liquid scintillation spectrometry [16–18]. The
nonsaturable component of [
14
C]Gly-Sar uptake (diffusion,
adherent radioactivity), determined by measuring the
uptake of [

14
C]Gly-Sar in the presence of 50 mm (Caco-2)
or 20 mm (SKPT) of unlabelled Gly-Sar, represented 8.0%
and 12.3% of total uptake, respectively. This value was
taken into account during nonlinear regression analysis of
inhibition constants (IC
50
).
The uptake of [
14
C]Gly-Sar into transfected HeLa-hPEPT1
and HeLa-hPEPT2 cells grown in 24-well plates was
performed 20–24 h post-transfection at room temperature in
the same manner, except that the tracer concentration was
20 lm.
Construction of pNKS-hPEPT1 and in vitro cRNA
synthesis
The X. laevis oocyte expression vector pNKS was kindly
provided by Professor G. Schmalzing (RWTH, Aachen,
Germany). This vector contains the 5¢ and 3¢ UTRs of the
X. laevis oocyte b-globin gene. To clone the transporter’s
cDNA into pNKS, AatII and XbaI restriction sites were
introduced at the 5¢ and 3¢ ends, respectively, by PCR. As
template, the pBluescript-hPEPT1 vector was used. After
restriction enzyme digestion, the PCR product was ligated
into the digested pNKS vector. The insertion of the correct
cDNA was verified by sequencing. The pNKS-hPEPT1
construct served as template for cRNA synthesis. After
linearizing the plasmids with NotI, cRNAs were synthesized
using the mMESSAGE mMACHINE

Ò
SP6 kit (Ambion,
Huntingdon, Cambridgeshire, UK). The cRNAs were
purified with the MEGAclearÔ kit (Ambion), and the
concentration was determined by UV absorbance at
260 nm. The cRNAs were stored at )80 °C [22].
Xenopus laevis oocytes expressing hPEPT1 and
electrophysiology
Oocytes were surgically removed from anaesthetized X. laevis
frogs, dissected and defolliculated as described by Riedel
et al. [23]. In brief, for anaesthesia, tricaine methane sulfo-
nate (Sigma-Aldrich) was used. The removed oocytes were
separated by collagenase treatment (2 mgÆmL
)1
) for 2 h.
Healthy-looking oocytes (stages V–VI) were manually
selected and 23 nL (1.1 lgÆlL
)1
) of cRNA solution of
hPEPT1 were injected per oocyte. Water-injected oocytes
were used as controls. Injected oocytes were maintained at
19 °C in modified Barth’s medium (5 mm Hepes ⁄ NaOH, pH
7.4, 100 mm NaCl, 1 mm KCl, 1 mm CaCl
2
,1mm MgCl
2
,
10 000 UÆmL
)1
penicillin and 10 mgÆmL

)1
streptomycin).
Five days postinjection, electrophysiological measurements
were performed. Oocytes were placed in a flow-through
chamber and continuously superfused (75 lLÆs
)1
) with
oocyte Ringer (ORi) buffer (10 mm Mes ⁄ Tris, pH 6.5,
100 mm NaCl, 1 mm MgCl
2
,1mm CaCl
2
,2mm KCl) in the
absence or presence of anserine and carnosine at a concentra-
tion of 10 mm. Quick and reproducible solution exchanges
were achieved using a small tube-like chamber (0.1 mL)
combined with fast superfusion [22–25]. Microelectrodes with
resistances between 0.8 and 1.4 MX were made of borosili-
cate glass and filled with 3 m KCl. Whole-cell currents were
recorded and filtered at 100 Hz using a two-electrode,
voltage-clamp amplifier (OC-725C, Hamden, USA) and
sampled at 85 Hz. Oocytes were voltage clamped at a
membrane potential of )60 mV.
Data analysis
Experiments were performed in duplicate or triplicate, and
each experiment was repeated two to three times. Results
are given as the means ± standard errors. The concentra-
tion of the unlabelled compound necessary to inhibit
50% of [
14

C]Gly-Sar carrier-mediated uptake was deter-
mined by nonlinear regression using the logistical equation
for an asymmetric sigmoid (allosteric Hill kinetics),
y = Min + (Max – Min) ⁄ [1 + (X ⁄ IC
50
)
)P
], where Max is
the initial Y value, Min is the final Y value and the power
P represents Hills’ coefficient (sigmaplot program, Systat,
Erkrath, Germany) [16–18]. Inhibitory constants (K
i
) were
calculated from the IC
50
values according to the method
developed by Cheng and Prusoff [19].
Oocyte data were analysed using the superpatch 2000
program (Julius-Bernstein-Institute of Physiology, SP-Ana-
lyzer by T. Bo
¨
hm, Halle, Germany). The statistical values
of the oocyte experiments were taken from the measure-
ments of three to seven oocytes each from two batches of
oocyte preparation. Currents induced by the application
of anserine and carnosine were calculated as the difference
in the currents measured in the presence and absence of
substrate.
Acknowledgements
This study was supported by Deutsche Forschungs-

gemeinschaft grant BR 2430 ⁄ 2-1 and by the State Sax-
ony-Anhalt Life Sciences Excellence Initiative Grant
#XB3599HP ⁄ 0105T. The authors thank Monika
Schmidt for excellent technical assistance.
References
1 Crush KG (1970) Carnosine and related substances in
animal tissues. Comp Biochem Physiol 34, 3–30.
2 Kubomura D, Matahira Y, Masui A & Matsuda H
(2009) Intestinal absorption and blood clearance of
l-histidine-related compounds after ingestion of
anserine in humans and comparison to anserine-
containing diets. J Agric Food Chem 57, 1781–
1785.
Anserine transport by peptide transporters S. Geissler et al.
794 FEBS Journal 277 (2010) 790–795 ª 2010 The Authors Journal compilation ª 2010 FEBS
3 Bauer K & Schulz M (1994) Biosynthesis of carnosine
and related peptides by skeletal muscle cells in primary
culture. Eur J Biochem 219, 43–47.
4 McManus R (1962) Enzymatic synthesis of anserine in
skeletal muscle by N-methylation of carnosine. J Biol
Chem 237, 1207–1211.
5 Aruoma OI, Laughton MJ & Halliwell B (1989)
Carnosine, homocarnosine and anserine: could they act
as antioxidants in vivo? Biochem J 264, 863–869.
6 Szwergold BS (2005) Carnosine and anserine act as
effective transglycating agents in decomposition of
aldose-derived Schiff bases. Biochem Biophys Res
Commun 336, 36–41.
7 Chan KM & Decker EA (1994) Endogenous skeletal
muscle antioxidants. Crit Rev Food Sci Nutr 34,

403–426.
8 Urazaev AKh, Naumenko NV, Nikolsky EE &
Vyskocil F (1998) Carnosine and other imidazole-
containing compounds enhance the postdenervation
depolarization of the rat diaphragm fibres. Physiol Res
47, 291–295.
9 Hama T, Tamaki N, Miyamoto F, Kita M &
Tsunemori F (1976) Intestinal absorption of b-alanine,
anserine and carnosine in rats. J Nutr Sci Vitaminol 22,
147–157.
10 Yeum K-J, Orioli M, Regazzoni L, Carini M,
Rasmussen H, Russell RM & Aldini G (2009) Profiling
histidine dipeptides in plasma and urine after ingesting
beef, chicken or chicken broth in humans. Amino Acids,
doi:10.1007/s00726-009-0291-2.
11 Daniel H (2004) Molecular and integrative physiology
of intestinal peptide transport. Annu Rev Physiol 66,
361–384.
12 Brandsch M (2009) Transport of drugs by proton-
coupled peptide transporters: pearls and pitfalls. Expert
Opin Drug Metab Toxicol 5, 887–905.
13 Matthews DM, Addison JM & Burston D (1974)
Evidence for active transport of the dipeptide carnosine
(b-alanyl-l-histidine) by hamster jejunum in vitro. Clin
Sci Mol Med 46, 693–705.
14 Ganapathy V & Leibach FH (1983) Role of pH
gradient and membrane potential in dipeptide transport
in intestinal and renal brush-border membrane vesicles
from the rabbit. Studies with l-carnosine and
glycyl-l-proline. J Biol Chem 258, 14189–14192.

15 Ganapathy V, Brandsch M & Leibach FH (1994)
Intestinal transport of amino acids and peptides. In
Physiology of the Gastrointestinal Tract, 3rd edn
(Johnson LR ed), pp. 1773–1794. Raven Press Ltd,
New York.
16 Brandsch M, Brandsch C, Prasad PD, Ganapathy V,
Hopfer U & Leibach FH (1995) Identification of a renal
cell line that constitutively expresses the kidney-specific
high-affinity H
+
⁄ peptide cotransporter. FASEB J 9,
1489–1496.
17 Knu
¨
tter I, Kottra G, Fischer W, Daniel H & Brandsch
M (2009) High-affinity interaction of sartans with
H
+
⁄ peptide transporters. Drug Metab Dispos 37,
143–149.
18 Neumann J, Bruch M, Gebauer S & Brandsch M
(2004) Transport of the phosphonodipeptide alafosfalin
by the H
+
⁄ peptide cotransporters PEPT1 and PEPT2
in intestinal and renal epithelial cells. Eur J Biochem
271, 2012–2017.
19 Cheng Y & Prusoff WH (1973) Relationship between the
inhibition constant (K
i

) and the concentration of inhibi-
tor which causes 50 per cent inhibition (I50) of an enzy-
matic reaction. Biochem Pharmacol 22, 3099–3108.
20 Lenney JF, Peppers SC, Kucera-Orallo CM & George
RP (1985) Characterization of human tissue carnosin-
ase. Biochem J 228, 653–660.
21 Pegova A, Abe H & Boldyrev A (2000) Hydrolysis of
carnosine and related compounds by mammalian
carnosinases. Comp Biochem Physiol B 127, 443–446.
22 Dorn M, Jaehme M, Weiwad M, Markwardt F,
Rudolph R, Brandsch M & Bosse-Doenecke E (2009)
The role of N-glycosylation in transport function and
surface targeting of the human solute carrier PAT1.
FEBS Lett 583, 1631–1636.
23 Riedel T, Lozinsky I, Schmalzing G & Markwardt F
(2007) Kinetics of P2X7 receptor-operated single
channel currents. Biophys J 92, 2377–2391.
24 Klapperstu
¨
ck M, Bu
¨
ttner C, Bo
¨
hm T, Schmalzing G &
Markwardt F (2000) Characteristics of P2X7 receptors
from human B lymphocytes expressed in Xenopus
oocytes. Biochim Biophys Acta 1467, 444–456.
25 Bretschneider F & Markwardt F (1999) Drug-dependent
ion channel gating by application of concentration
jumps using U-tube technique. Methods Enzymol 294,

180–189.
S. Geissler et al. Anserine transport by peptide transporters
FEBS Journal 277 (2010) 790–795 ª 2010 The Authors Journal compilation ª 2010 FEBS 795