The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Douglas J Morrison - One of the best experts on this subject based on the ideXlab platform.
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the effect of l Rhamnose on intestinal transit time short chain fatty acids and appetite regulation a pilot human study using combined 13co2 h2 breath tests
Journal of Breath Research, 2018Co-Authors: Claire S Byrne, T Preston, Jerusa Brignardello, Isabel Garciaperez, Elaine Holmes, Gary Frost, Douglas J MorrisonAbstract:BACKGROUND: The appetite-regulating effects of non-digestible carbohydrates (NDC) have in part previously been attributed to their effects on intestinal transit rates as well as microbial production of short chain fatty acids (SCFA). Increased colonic production of the SCFA propionate has been shown to reduce energy intake and stimulate gut hormone secretion acutely in humans. OBJECTIVE: We investigated the effect of the propiogenic NDC, L-Rhamnose, on gastrointestinal transit times using a combined 13CO2/H2 breath test. We hypothesised that L-Rhamnose would increase plasma propionate leading to a reduction in appetite, independent of changes in gastrointestinal transit times. DESIGN: We used a dual 13C-octanoic acid/lactose 13C-ureide breath test combined with breath H2 to measure intestinal transit times following the consumption of 25 g d-1 L-Rhamnose, compared with inulin and cellulose, in 10 healthy humans in a randomised cross-over design pilot study. Gastric emptying (GE) and oro-caecal transit times (OCTTs) were derived from the breath 13C data and compared with breath H2. Plasma SCFA and peptide YY (PYY) were also measured alongside subjective measures of appetite. RESULTS: L-Rhamnose significantly slowed GE rates (by 19.5 min) but there was no difference in OCTT between treatments. However, breath H2 indicated fermentation of L-Rhamnose before it reached the caecum. OCTT was highly correlated with breath H2 for inulin but not for L-Rhamnose or cellulose. L-Rhamnose consumption significantly increased plasma propionate and PYY but did not significantly reduce subjective appetite measures. CONCLUSIONS: The NDCs tested had a minimal effect on intestinal transit time. Our data suggest that L-Rhamnose is partially fermented in the small intestine and that breath H2 reflects the site of gastrointestinal fermentation and is only a reliable marker of OCTT for certain NDCs (e.g. inulin). Future studies should focus on investigating the appetite-suppressing potential of L-Rhamnose and verifying the findings in a larger cohort.
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the effect of l Rhamnose on intestinal transit time short chain fatty acids and appetite regulation a pilot human study using combined 13co2 h2 breath tests
Journal of Breath Research, 2018Co-Authors: Claire S Byrne, T Preston, Jerusa Brignardello, Isabel Garciaperez, Elaine Holmes, Gary Frost, Douglas J MorrisonAbstract:Background: The appetite-regulating effects of non-digestible carbohydrates (NDC) have in part previously been attributed to their effects on intestinal transit rates as well as microbial production of short chain fatty acids (SCFA). Increased colonic production of the SCFA propionate has been shown to reduce energy intake and stimulate gut hormone secretion acutely in humans. Objective: We investigated the effect of the propiogenic NDC, L-Rhamnose, on gastrointestinal transit times using a combined 13CO2/H2 breath test. We hypothesised that L-Rhamnose would increase plasma propionate leading to a reduction in appetite, independent of changes in gastrointestinal transit times. Design: We used a dual 13C octanoic acid/lactose 13C-ureide breath test combined with breath H2 to measure intestinal transit times following the consumption of 25g/d L-Rhamnose, compared with inulin and cellulose, in 10 healthy humans in a randomised cross-over pilot study. Gastric emptying (GE) and oro-caecal transit times (OCTT) were derived from the breath 13C data and compared with breath H2. Plasma SCFA and peptide YY (PYY) were also measured alongside subjective measures of appetite. Results: L-Rhamnose significantly slowed GE rates (by 19.5min) but there was no difference in OCTT between treatments. However, breath H2 indicated fermentation of L-Rhamnose before it reached the caecum. OCTT was highly correlated with breath H2 for inulin but not for L-Rhamnose or cellulose. L-Rhamnose consumption significantly increased plasma propionate and PYY but did not significantly reduce subjective appetite measures. Conclusions: The NDCs tested had a minimal effect on intestinal transit time. Our data suggest that L-Rhamnose is partially fermented in the small intestine and that breath H2 reflects the site of gastrointestinal fermentation and is only a reliable marker of OCTT for certain NDCs (e.g. inulin). Future studies should focus on investigating the appetite-suppressing potential of L-Rhamnose and verifying the findings in a larger cohort.
Brian W. Matthews - One of the best experts on this subject based on the ideXlab platform.
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The Structure of Rhamnose Isomerase from Escherichia coli and its Relation with Xylose Isomerase Illustrates a Change Between Inter and Intra-subunit Complementation During Evolution
2013Co-Authors: Ingo Korndoè P. Rfer, Wolf-dieter Fessner, Brian W. Matthews, Howard Hughes MedicalAbstract:Using a new expression construct, Rhamnose isomerase from Escherichia coli was puri®ed and crystallized. The crystal structure was solved by multiple isomorphous replacement and re®ned to a crystallographic residual of 17.4 % at 1.6 AÊ resolution. Rhamnose isomerase is a tight tetramer of four (b/a) 8-barrels. A comparison with other known structures reveals that Rhamnose isomerase is most similar to xylose isomerase. Alignment of the sequences of the two enzymes based on their structures reveals a hitherto undetected sequence identity of 13 %, suggesting that the two enzymes evolved from a common precursor. The structure and arrangement of the (b/a) 8-barrels of Rhamnose isomerase are very similar to xylose isomerase. Each enzyme does, however, have additional a-helical domains, which are involved in tetramer association, and largely differ in structure. The structures of complexes of Rhamnose isomerase with the inhibitor L-rhamnitol and the natural substrate L-Rhamnose were determined and suggest that an extended loop, which is disordered i
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The structure of Rhamnose isomerase from Escherichia coli and its relation with xylose isomerase illustrates a change between inter and intra-subunit complementation during evolution.
Journal of Molecular Biology, 2000Co-Authors: Ingo P. Korndörfer, Wolf-dieter Fessner, Brian W. MatthewsAbstract:Using a new expression construct, Rhamnose isomerase from Escherichia coli was purified and crystallized. The crystal structure was solved by multiple isomorphous replacement and refined to a crystallographic residual of 17.4 % at 1.6 Aresolution. Rhamnose isomerase is a tight tet- ramer of four (b/a)8-barrels. A comparison with other known structures reveals that Rhamnose isomerase is most similar to xylose isomerase. Alignment of the sequences of the two enzymes based on their structures reveals a hitherto undetected sequence identity of 13 %, suggesting that the two enzymes evolved from a common precursor. The structure and arrangement of the (b/a)8-barrels of Rhamnose isomerase are very similar to xylose isomerase. Each enzyme does, however, have additional a-heli- cal domains, which are involved in tetramer association, and largely dif- fer in structure. The structures of complexes of Rhamnose isomerase with the inhibitor L-rhamnitol and the natural substrate L-Rhamnose were determined and suggest that an extended loop, which is disordered in the native enzyme, becomes ordered on substrate binding, and may exclude bulk solvent during catalysis. Unlike xylose isomerase, this loop does not extend across a subunit interface but contributes to the active site of its own subunit. It illustrates how an interconversion between inter and intra-subunit complementation can occur during evolution. In the crystal structure (although not necessarily in vivo) Rhamnose isomer- ase appears to bind Zn 2a at a ''structural'' site. In the presence of sub- strate the enzyme also binds Mn 2a at a nearby ''catalytic'' site. An array of hydrophobic residues, not present in xylose isomerase, is likely to be responsible for the recognition of L-Rhamnose as a substrate. The avail- able structural data suggest that a metal-mediated hydride-shift mechan- ism, which is generally favored for xylose isomerase, is also feasible for Rhamnose isomerase. # 2000 Academic Press
Helge C. Dorfmueller - One of the best experts on this subject based on the ideXlab platform.
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NDP-Rhamnose biosynthesis and rhamnosyltransferases: building diverse glycoconjugates in nature.
The Biochemical journal, 2021Co-Authors: Ben A. Wagstaff, Azul Zorzoli, Helge C. DorfmuellerAbstract:Rhamnose is an important 6-deoxy sugar present in many natural products, glycoproteins, and structural polysaccharides. Whilst predominantly found as the l-enantiomer, instances of d-Rhamnose are also found in nature, particularly in the Pseudomonads bacteria. Interestingly, Rhamnose is notably absent from humans and other animals, which poses unique opportunities for drug discovery targeted towards Rhamnose utilizing enzymes from pathogenic bacteria. Whilst the biosynthesis of nucleotide-activated Rhamnose (NDP-Rhamnose) is well studied, the study of rhamnosyltransferases that synthesize Rhamnose-containing glycoconjugates is the current focus amongst the scientific community. In this review, we describe where Rhamnose has been found in nature, as well as what is known about TDP-β-l-Rhamnose, UDP-β-l-Rhamnose, and GDP-α-d-Rhamnose biosynthesis. We then focus on examples of rhamnosyltransferases that have been characterized using both in vivo and in vitro approaches from plants and bacteria, highlighting enzymes where 3D structures have been obtained. The ongoing study of Rhamnose and rhamnosyltransferases, in particular in pathogenic organisms, is important to inform future drug discovery projects and vaccine development.
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Streptococcal dTDP‐L‐Rhamnose biosynthesis enzymes: functional characterization and lead compound identification
Molecular microbiology, 2019Co-Authors: Samantha L. Van Der Beek, Azul Zorzoli, Ebru Çanak, Robert N Chapman, Kieron Lucas, Benjamin H. Meyer, Dimitrios Evangelopoulos, Luiz Pedro S. De Carvalho, Geert-jan Boons, Helge C. DorfmuellerAbstract:Biosynthesis of the nucleotide sugar precursor dTDP-L-Rhamnose is critical for the viability and virulence of many human pathogenic bacteria, including Streptococcus pyogenes (Group A Streptococcus; GAS), Streptococcus mutans and Mycobacterium tuberculosis. Streptococcal pathogens require dTDP-L-Rhamnose for the production of structurally similar Rhamnose polysaccharides in their cell wall. Via heterologous expression in S. mutans, we confirmed that GAS RmlB and RmlC are critical for dTDP-L-Rhamnose biosynthesis through their action as dTDP-glucose-4,6-dehydratase and dTDP-4-keto-6-deoxyglucose-3,5-epimerase enzymes respectively. Complementation with GAS RmlB and RmlC containing specific point mutations corroborated the conservation of previous identified catalytic residues. Bio-layer interferometry was used to identify and confirm inhibitory lead compounds that bind to GAS dTDP-Rhamnose biosynthesis enzymes RmlB, RmlC and GacA. One of the identified compounds, Ri03, inhibited growth of GAS, other Rhamnose-dependent streptococcal pathogens as well as M. tuberculosis with an IC 50 of 120–410 µM. Importantly, we confirmed that Ri03 inhibited dTDP-L-Rhamnose formation in a concentration-dependent manner through a biochemical assay with recombinant Rhamnose biosynthesis enzymes. We therefore conclude that inhibitors of dTDP-L-Rhamnose biosynthesis, such as Ri03, affect streptococcal and mycobacterial viability and can serve as lead compounds for the development of a new class of antibiotics that targets dTDP-Rhamnose biosynthesis in pathogenic bacteria.
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Streptococcal dTDP-L-Rhamnose biosynthesis enzymes: functional characterization and lead compound identification
2018Co-Authors: Samantha L. Van Der Beek, Azul Zorzoli, Ebru Çanak, Robert N Chapman, Benjamin H. Meyer, Geert-jan Boons, Helge C. Dorfmueller, Nina M. Van SorgeAbstract:Summary Biosynthesis of the nucleotide sugar precursor dTDP-L-Rhamnose is critical for the viability and virulence of many human pathogenic bacteria, including Streptococcus pyogenes (Group A Streptococcus; GAS) and Streptococcus mutans. Those pathogens require dTDP-L-Rhamnose for the production of structurally similar Rhamnose polysaccharides in their cell wall. Via heterologous expression in S. mutans, we confirm that GAS RmlB and RmlC are critical for dTDP-L-Rhamnose biosynthesis through their action as dTDP-glucose-4,6-dehydratase and dTDP-4-keto-6-deoxyglucose-3,5-epimerase enzymes, respectively. Complementation with GAS RmlB and RmlC containing specific point mutations corroborated the conservation of previous identified catalytic residues in these enzymes. Bio-layer interferometry was used to identify and confirm inhibitory lead compounds that bind to GAS dTDP-Rhamnose biosynthesis enzymes RmlB, RmlC and GacA. One of the identified compounds, Ri03, inhibited growth of GAS as well as several other Rhamnose-dependent streptococcal pathogens with an MIC50 of 120-410 μM. We therefore conclude that inhibition of dTDP-L-Rhamnose biosynthesis such as Ri03 affect streptococcal viability and can serve as a lead compound for the development of a new class of antibiotics that targets dTDP-Rhamnose biosynthesis in pathogenic bacteria.
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identification of lead compounds targeting the dtdp l Rhamnose biosynthesis pathway using streptococcus pyogenes
bioRxiv, 2018Co-Authors: Samantha L. Van Der Beek, Azul Zorzoli, Ebru Çanak, Robert N Chapman, Benjamin H. Meyer, Geert-jan Boons, Helge C. Dorfmueller, Nina M. Van SorgeAbstract:Biosynthesis of the nucleotide sugar precursor dTDP-L-Rhamnose is critical for the viability and virulence of many human pathogenic bacteria, including Streptococcus pyogenes (Group A Streptococcus; GAS) and Streptococcus mutans. Both pathogens require dTDP-L-Rhamnose for the production of a structurally similar Rhamnose-containing polysaccharide in their cell wall. Via heterologous expression in S. mutans, we confirm that GAS RmlB and RmlC are critical for dTDP-L-Rhamnose biosynthesis through their action as dTDP-glucose-4,6-dehydratase and dTDP-4-keto-6-deoxyglucose-3,5-epimerase enzymes, respectively. Complementation with GAS RmlB and RmlC containing specific point mutations corroborated the conservation of previous identified amino acids in the catalytic site of these enzymes. Bio-layer interferometry was used to identify inhibitory lead compounds that bind directly to GAS dTDP-Rhamnose biosynthesis enzymes RmlB, RmlC and GacA in a concentration-dependent manner. One of the identified compounds, Ri03, inhibited growth of GAS as well as several other streptococcal pathogens with an MIC50 of 120-410 μM. Ri03 displayed no cytotoxity in U937 monocytic cells up to a concentration of 15 mM. We therefore conclude that Ri03 can serve as a lead compound for the development of a new class of antibiotics that targets dTDP-Rhamnose biosynthesis in pathogenic bacteria.
Claire S Byrne - One of the best experts on this subject based on the ideXlab platform.
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the effect of l Rhamnose on intestinal transit time short chain fatty acids and appetite regulation a pilot human study using combined 13co2 h2 breath tests
Journal of Breath Research, 2018Co-Authors: Claire S Byrne, T Preston, Jerusa Brignardello, Isabel Garciaperez, Elaine Holmes, Gary Frost, Douglas J MorrisonAbstract:BACKGROUND: The appetite-regulating effects of non-digestible carbohydrates (NDC) have in part previously been attributed to their effects on intestinal transit rates as well as microbial production of short chain fatty acids (SCFA). Increased colonic production of the SCFA propionate has been shown to reduce energy intake and stimulate gut hormone secretion acutely in humans. OBJECTIVE: We investigated the effect of the propiogenic NDC, L-Rhamnose, on gastrointestinal transit times using a combined 13CO2/H2 breath test. We hypothesised that L-Rhamnose would increase plasma propionate leading to a reduction in appetite, independent of changes in gastrointestinal transit times. DESIGN: We used a dual 13C-octanoic acid/lactose 13C-ureide breath test combined with breath H2 to measure intestinal transit times following the consumption of 25 g d-1 L-Rhamnose, compared with inulin and cellulose, in 10 healthy humans in a randomised cross-over design pilot study. Gastric emptying (GE) and oro-caecal transit times (OCTTs) were derived from the breath 13C data and compared with breath H2. Plasma SCFA and peptide YY (PYY) were also measured alongside subjective measures of appetite. RESULTS: L-Rhamnose significantly slowed GE rates (by 19.5 min) but there was no difference in OCTT between treatments. However, breath H2 indicated fermentation of L-Rhamnose before it reached the caecum. OCTT was highly correlated with breath H2 for inulin but not for L-Rhamnose or cellulose. L-Rhamnose consumption significantly increased plasma propionate and PYY but did not significantly reduce subjective appetite measures. CONCLUSIONS: The NDCs tested had a minimal effect on intestinal transit time. Our data suggest that L-Rhamnose is partially fermented in the small intestine and that breath H2 reflects the site of gastrointestinal fermentation and is only a reliable marker of OCTT for certain NDCs (e.g. inulin). Future studies should focus on investigating the appetite-suppressing potential of L-Rhamnose and verifying the findings in a larger cohort.
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the effect of l Rhamnose on intestinal transit time short chain fatty acids and appetite regulation a pilot human study using combined 13co2 h2 breath tests
Journal of Breath Research, 2018Co-Authors: Claire S Byrne, T Preston, Jerusa Brignardello, Isabel Garciaperez, Elaine Holmes, Gary Frost, Douglas J MorrisonAbstract:Background: The appetite-regulating effects of non-digestible carbohydrates (NDC) have in part previously been attributed to their effects on intestinal transit rates as well as microbial production of short chain fatty acids (SCFA). Increased colonic production of the SCFA propionate has been shown to reduce energy intake and stimulate gut hormone secretion acutely in humans. Objective: We investigated the effect of the propiogenic NDC, L-Rhamnose, on gastrointestinal transit times using a combined 13CO2/H2 breath test. We hypothesised that L-Rhamnose would increase plasma propionate leading to a reduction in appetite, independent of changes in gastrointestinal transit times. Design: We used a dual 13C octanoic acid/lactose 13C-ureide breath test combined with breath H2 to measure intestinal transit times following the consumption of 25g/d L-Rhamnose, compared with inulin and cellulose, in 10 healthy humans in a randomised cross-over pilot study. Gastric emptying (GE) and oro-caecal transit times (OCTT) were derived from the breath 13C data and compared with breath H2. Plasma SCFA and peptide YY (PYY) were also measured alongside subjective measures of appetite. Results: L-Rhamnose significantly slowed GE rates (by 19.5min) but there was no difference in OCTT between treatments. However, breath H2 indicated fermentation of L-Rhamnose before it reached the caecum. OCTT was highly correlated with breath H2 for inulin but not for L-Rhamnose or cellulose. L-Rhamnose consumption significantly increased plasma propionate and PYY but did not significantly reduce subjective appetite measures. Conclusions: The NDCs tested had a minimal effect on intestinal transit time. Our data suggest that L-Rhamnose is partially fermented in the small intestine and that breath H2 reflects the site of gastrointestinal fermentation and is only a reliable marker of OCTT for certain NDCs (e.g. inulin). Future studies should focus on investigating the appetite-suppressing potential of L-Rhamnose and verifying the findings in a larger cohort.
Jianjun Pei - One of the best experts on this subject based on the ideXlab platform.
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Enhancing UDP-Rhamnose Supply for Rhamnosylation of Flavonoids in Escherichia coli by Regulating the Modular Pathway and Improving NADPH Availability.
Journal of agricultural and food chemistry, 2020Co-Authors: Cong Qiu, Linguo Zhao, Lihu Zhang, Jianjun PeiAbstract:UDP-Rhamnose is the main type of sugar donor and endows flavonoids with special activity, selectivity, and pharmacological properties by glycosylation. In this study, several UDP-glucose synthesis pathways and UDP-Rhamnose synthases were screened to develop an efficient UDP-Rhamnose biosynthesis pathway in Escherichia coli. Maximal UDP-Rhamnose production reached 82.2 mg/L in the recombinant strain by introducing the cellobiose phosphorolysis pathway and Arabidopsis thaliana UDP-Rhamnose synthase (AtRHM). Quercitrin production of 3522 mg/L was achieved in the recombinant strain by coupling the UDP-Rhamnose generation system with A. thaliana rhamnosyltransferase (AtUGT78D1) to recycle UDP-Rhamnose. To further increase UDP-Rhamnose supply, an NADPH-independent fusion enzyme was constructed, the UTP supply was improved, and NADPH regenerators were overexpressed in vivo. Finally, by optimizing the bioconversion conditions, the highest quercitrin production reached 7627 mg/L with the average productivity of 141 mg/(L h), which is the highest yield of quercitrin and efficiency of UDP-Rhamnose supply reported to date in E. coli. Therefore, the method described herein for the regeneration of UDP-Rhamnose from cellobiose may be widely used for the rhamnosylation of flavonoids and other bioactive substances.
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Construction of a novel UDP-Rhamnose regeneration system by a two-enzyme reaction system and application in glycosylation of flavonoid
Biochemical Engineering Journal, 2018Co-Authors: Jianjun Pei, Linguo Zhao, Anna Chen, Qing Sun, Fuliang Cao, Feng TangAbstract:Abstract UDP-Rhamnose is synthesized by UDP-Rhamnose synthase, but the reaction requires two kinds of cofactors, NAD+ and NADPH. In this work, a cofactor self-sufficient UDP-Rhamnose regeneration system was described herein. The UDP-Rhamnose synthase (VvRHM) gene from Vitis vinifera was cloned and expressed in Escherichia coli and characterizations of VvRHM were determined. The N-terminal region of VvRHM was fused with the bifunctional UDP-4-keto-6-deoxy- d -glucose 3,5-epimerase/UDP-4-keto-Rhamnose 4-keto-reductase (NRS/ER) from Arabidopsis thaliana to obtain the fusion enzyme (VvRHM-NRS), which was NADPH-independent and could convert UDP-glucose to UDP-Rhamnose with NADH self-sufficient. The optimal activity of VvRHM-NRS was at pH 7.5 and 30 °C. Apparent Km and Vmax of VvRHM-NRS for UDP-glucose were 88 ± 9 μM and 12.7 ± 0.6 nmol/min/mg, and for NAD+ were 69 ± 7 μM and 11.9 ± 0.5 nmol/min/mg. Then, a novel process for the synthesis of UDP-Rhamnose from sucrose, NAD+, and UDP was developed by using VvRHM-NRS coupled with Glycine max sucrose synthase (GmSUS). By optimizing coupled reaction conditions, UDP-Rhamnose production reached 0.57 mM. Finally, UDP-Rhamnose regeneration system was tested to synthesize quercitrin with A. thaliana glycosyltransferase (AtUGT78D1). Therefore, VvRHM-NRS coupled with GmSUS presented a green chemistry approach for the UDP-Rhamnose regeneration in glycosylation of flavonoids and other bioactive substances.
