15 research outputs found
Both PepT1 and GLUT Intestinal Transporters Are Utilized by a Novel Glycopeptide Pro-Hyp-CONH-GlcN
Pro-Hyp
(PO) accounts for many beneficial biological effects of
collagen hydrolysates for skin and bone health. The objective of this
study was to conjugate PO with glucosamine (GlcN) to create a novel
glycopeptide Pro-Hyp-CONH-GlcN (POGlcN) and then to investigate the
potential involvement of multiple transepithelial transport pathways
for this glycopeptide. Nuclear magnetic resonance results revealed
the amide nature of this glycopeptide with α and β configurations
derived from GlcN. This glycopeptide was very resistant to simulated
gastrointestinal digestion. Also, it showed a rate of transepithelial
transport [permeability coefficient (<i>P</i><sub>app</sub>) of (2.82 ± 0.15) × 10<sup>–6</sup> cm/s] across
the Caco-2 cell monolayer superior to those of parental dipeptide
PO and GlcN [<i>P</i><sub>app</sub> values of (1.45 ±
0.17) × 10<sup>–6</sup> and (1.87 ± 0.15) ×
10<sup>–6</sup> cm/s, respectively]. A transport mechanism
experiment indicated that the improved transport efficiency of POGlcN
is attributed to the introduction of glucose transporters
Identification and Evaluation of Cryoprotective Peptides from Chicken Collagen: Ice-Growth Inhibition Activity Compared to That of Type I Antifreeze Proteins in Sucrose Model Systems
The ability of chicken
collagen peptides to inhibit the growth
of ice crystals was evaluated and compared to that of fish antifreeze
proteins (AFPs). This ice inhibition activity was assessed using a
polarized microscope by measuring ice crystal dimensions in a sucrose
model system with and without collagen peptides after seven thermal
cycles. The system was stabilized at −25 °C and cycled
between −16 and −12 °C. Five candidate peptides
with ice inhibition activity were identified using liquid chromatography
and tandem mass spectrometry and were then synthesized. Their ice
inhibition capacity was compared to that of type I AFPs in a 23% sucrose
model system. Specific collagen peptides with certain amino acid sequences
reduced the extent of ice growth by approximately 70% at a relatively
low concentration (1 mg/mL). These results suggest that specific collagen
peptides may act in a noncolligative manner, inhibiting ice crystal
growth like type I AFPs, but less efficiently
Studies on the Formation of Maillard and Caramelization Products from Glucosamine Incubated at 37 °C
This experiment compared the in vitro
degradation of glucosamine
(GlcN), <i>N</i>-acetylglucosamine, and glucose in the presence
of NH<sub>3</sub> incubated at 37 °C in phosphate buffer from
0.5 to 12 days. The reactions were monitored with UV–vis absorption
and fluorescence emission spectroscopies, and the main products of
degradation, quinoxaline derivatives of α-dicarbonyl compounds
and condensation products, were determined using UHPLC-UV and Orbitrap
mass spectrometry. GlcN produced two major dicarbonyl compounds, glucosone
and 3-deoxyglucosone, ranging from 709 to 3245 mg/kg GlcN and from
272 to 4535 mg/kg GlcN, respectively. 3,4-Dideoxyglucosone-3-ene,
glyoxal, hydroxypyruvaldehyde, methylglyoxal, and diacetyl were also
detected in lower amounts compared to glucosone and 3-deoxyglucosone.
Several pyrazine condensation products resulting from the reaction
between dicarbonyls and GlcN were also identified. This study determined
that GlcN is a significantly unstable molecule producing a high level
of degradation products at 37 °C
Transport of the Glucosamine-Derived Browning Product Fructosazine (Polyhydroxyalkylpyrazine) Across the Human Intestinal Caco‑2 Cell Monolayer: Role of the Hexose Transporters
The
transport mechanism of fructosazine, a glucosamine self-condensation
product, was investigated using a Caco-2 cell model. Fructosazine
transport was assessed by measuring the bidirectional permeability
coefficient across Caco-2 cells. The mechanism of transport was evaluated
using phlorizin, an inhibitor of sodium-dependent glucose cotransporters
(SGLT) 1 and 2, phloretin and quercetin, inhibitors of glucose transporters
(GLUT) 1 and 2, transcytosis inhibitor wortmannin, and gap junction
disruptor cytochalasin D. The role of hexose transporters was further
studied using downregulated or overexpressed cell lines. The apparent
permeability (<i>P</i><sub>a,b</sub>) of fructosazine was
1.30 ± 0.02 × 10<sup>–6</sup> cm/s. No significant
(<i>p</i> > 0.05) effect was observed in fructosazine
transport
by adding wortmannin and cytochalasin D. The presence of phlorizin,
phloretin, and quercetin decreased fructosazine transport. The downregulated
GLUT cells line was unable to transport fructosazine. In human intestinal
epithelial Caco-2 cells, GLUT1 or GLUT2 and SGLT are mainly responsible
for fructosazine transport
A deconvoluted ESI-MS spectra of Mb incubated at 37°C for various times in the presence of GlcNAc, Glc and GlcN.
<p>The experimental conditions were the same as those used to obtain the spectra in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0139022#pone.0139022.g001" target="_blank">Fig 1</a>. Inset spectrum (A) shows the spectrum of GlcN incubated for 12 days in the region of 7000–18000 Da.</p
Concentration of the major α-dicarbonyl compound produced during incubation of Mb in the presence of GlcN from 0 to 12 days.
<p>The values are represented as mean ± standard deviation (calculated from three independent trials). G, glucosone; 3-DG, 3-deoxyglucosone; GO, glyoxal; MGO, methylglyoxal; DA, diacetyl. Different letters within each α-dicarbonyl compound indicate statistical significant difference (<i>p</i> < 0.05).</p
Fructosazine, a Polyhydroxyalkylpyrazine with Antimicrobial Activity: Mechanism of Inhibition against Extremely Heat Resistant <i>Escherichia coli</i>
Fructosazine
is a polyhydroxyalkylpyrazine recently reported to
have antimicrobial activity against heat-resistant <i>Escherichia
coli</i> AW 1.7. This study investigated fructosazine’s
antimicrobial mechanism of action and compared it to that of riboflavin.
Fructosazine–acetic acid was effective in permeabilizing the
outer membrane based on an evaluation of bacterial membrane integrity
using 1-<i>N-</i>phenyl-1-naphthylamine and propidium iodide.
The uptake of fructosazine by <i>E. coli</i> was pH-dependent
with a greater uptake at pH 5 compared to pH 7 for all times throughout
16 h, except 2, 3, and 10 h. Fructosazine generates <sup>1</sup>O<sub>2</sub>, which is partially why it damages <i>E. coli</i>. DNA fragmentation was confirmed by fluorescence microscopy, and
the fructosazine–acetic acid was the second most intense treatment
after riboflavin–acetic acid. Electron microscopy revealed
membrane structural damage by fructosazine at pH 5 and 7. This study
provides evidence that fructosazine exerts antimicrobial action by
permeabilizing the cell membrane, damaging membrane integrity, and
fragmenting DNA
Rapid Myoglobin Aggregation through Glucosamine-Induced α-Dicarbonyl Formation
<div><p>The extent of glycation and conformational changes of horse myoglobin (Mb) upon glycation with <i>N</i>-acetyl-glucosamine (GlcNAc), glucose (Glc) and glucosamine (GlcN) were investigated. Among tested sugars, the rate of glycation with GlcN was the most rapid as shown by MALDI and ESI mass spectrometries. Protein oxidation, as evaluated by the amount of carbonyl groups present on Mb, was found to increase exponentially in Mb-Glc conjugates over time, whereas in Mb-GlcN mixtures the carbonyl groups decreased significantly after maximum at 3 days of the reaction. The reaction between GlcN and Mb resulted in a significantly higher amount of α-dicarbonyl compounds, mostly glucosone and 3-deoxyglucosone, ranging from and 27 to 332 mg/L and from 14 to 304 mg/L, respectively. Already at 0.5 days, tertiary structural changes of Mb-GlcN conjugate were observed by altered tryptophan fluorescence. A reduction of metmyoglobin to deoxy-and oxymyoglobin forms was observed on the first day of reaction, coinciding with the greatest amount of glucosone produced. In contrast to native α-helical myoglobin, 41% of the glycated protein sequence was transformed into a β-sheet conformation, as determined by circular dichroism spectropolarimetry. Transmission electron microscopy demonstrated that Mb glycation with GlcN causes the formation of amorphous or fibrous aggregates, started already at 3 reaction days. These aggregates bind to an amyloid-specific dye thioflavin T. With the aid of α-dicarbonyl compounds and advanced products of reaction, this study suggests that the Mb glycation with GlcN induces the unfolding of an initially globular protein structure into amyloid fibrils comprised of a β-sheet structure.</p></div
UHPLC analyses of quinoxaline derivatives of α-dicarbonyl compounds produced from Mb-GlcN conjugates over time.
<p>(A) Chromatograms of (I) a reference quinoxaline mixture of glucosone (G), 3-deoxyglucosone (3-DG), glyoxal (GO), methylglyoxal (MGO) and diacetyl (DA). (II) Representative chromatogram of Mb-GlcN conjugate incubated for 1 d, derivatized with <i>o</i>-OPD and acquired by UHPLC with UV detection at 314 nm. Numbers indicate the peaks of the quinoxalines of (1) G, (2) unidentified, (3) 3-DG, (4) GO, (5) HPA, (6) 3,4- DGE, (7) MGO, (8) DA and a, b, c peaks corresponding to non-OPD derived GlcN condensation products.</p
Retention time, MS and MS/MS data of the α-dicarbonyl compounds detected Mb-GlcN conjugates.
<p>Retention time, MS and MS/MS data of the α-dicarbonyl compounds detected Mb-GlcN conjugates.</p