UNIPROT:P43026 - FACTA Search

Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P43026 (lipopolysaccharide)
62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Modification of the lipid A moiety of lipopolysaccharide by the addition of the sugar 4-amino-4-deoxy-L-arabinose (L-Ara4N) is a strategy adopted by pathogenic Gram-negative bacteria to evade cationic antimicrobial peptides produced by the innate immune system. L-Ara4N biosynthesis is therefore a potential anti-infective target, because inhibiting its synthesis would render certain pathogens more sensitive to the immune system. The bifunctional enzyme ArnA, which is required for L-Ara4N biosynthesis, catalyzes the NAD(+)-dependent oxidative decarboxylation of UDP-glucuronic acid to generate a UDP-4'-keto-pentose sugar and also catalyzes transfer of a formyl group from N-10-formyltetrahydrofolate to the 4'-amine of UDP-L-Ara4N. We now report the crystal structure of the N-terminal formyltransferase domain in a complex with uridine monophosphate and N-5-formyltetrahydrofolate. Using this structure, we identify the active site of formyltransfer in ArnA, including the key catalytic residues Asn(102), His(104), and Asp(140). Additionally, we have shown that residues Ser(433) and Glu(434) of the decarboxylase domain are required for the oxidative decarboxylation of UDP-GlcUA. An E434Q mutant is inactive, suggesting that chemical rather than steric properties of this residue are crucial in the decarboxylation reaction. Our data suggest that the decarboxylase domain catalyzes both hydride abstraction (oxidation) from the C-4' position and the subsequent decarboxylation.
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PMID:Structure and function of both domains of ArnA, a dual function decarboxylase and a formyltransferase, involved in 4-amino-4-deoxy-L-arabinose biosynthesis. 1580 94

In Escherichia coli and Salmonella enterica, the core oligosaccharide backbone of the lipopolysaccharide is modified by phosphoryl groups. The negative charges provided by these residues are important in maintaining the barrier function of the outer membrane. In contrast, Klebsiella pneumoniae lacks phosphoryl groups in its core oligosaccharide but instead contains galacturonic acid residues that are proposed to serve a similar function in outer membrane stability. Gla(KP) is a UDP-galacturonic acid C4-epimerase that provides UDP-galacturonic acid for core synthesis, and the enzyme was biochemically characterized because of its potentially important role in outer membrane stability. High-performance anion-exchange chromatography was used to demonstrate the UDP-galacturonic acid C4-epimerase activity of Gla(KP), and capillary electrophoresis was used for activity assays. The reaction equilibrium favors UDP-galacturonic acid over UDP-glucuronic acid in a ratio of 1.4:1, with the K(m) for UDP-glucuronic acid of 13.0 microM. Gla(KP) exists as a dimer in its native form. NAD+/NADH is tightly bound by the enzyme and addition of supplementary NAD+ is not required for activity of the purified enzyme. Divalent cations have an unexpected inhibitory effect on enzyme activity. Gla(KP) was found to have a broad substrate specificity in vitro; it is capable of interconverting UDP-glucose/UDP-galactose and UDP-N-acetylglucosamine/UDP-N-acetylgalactosamine, albeit at much lower activity. The epimerase GalE interconverts UDP-glucose/UDP-galactose. Multicopy plasmid-encoded gla(KP) partially complemented a galE mutation in S. enterica and in K. pneumoniae; however, chromosomal gla(KP) could not substitute for galE in a K. pneumoniae galE mutant in vivo.
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PMID:Characterization of Gla(KP), a UDP-galacturonic acid C4-epimerase from Klebsiella pneumoniae with extended substrate specificity. 1593 73

Pro-inflammatory cytokines, e.g. interleukin-1beta (IL-1beta), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNFalpha) as well as neurotoxic molecules such as nitric oxide (NO), that are produced and released by activated glial cells, play an important role in inflammation and oxidative stress occurring during Multiple Sclerosis (MS). Reduction of these processes could therefore be of therapeutic interest. Dimethylfumarate (DMF) and sulforaphane (SP) are well known for their detoxicating properties. Furthermore, they have anti-inflammatory effects as shown clinically by the treatment of inflammatory skin diseases. However, their detoxication and anti-inflammatory action on brain-derived cells is unknown. In the present study we have studied, within the same concentration range, the anti-inflammatory and detoxicating effects of DMF and SP on the production and release of mediators of inflammation and detoxication from lipopolysaccharide (LPS) activated primary co-cultures of rat microglial and astroglial cells. DMF and SP attenuated the LPS-induced production and release of TNFalpha, IL-1beta, IL-6 and NO. In addition, DMF and SP increase both mRNA level and activity of NAD(P)H:quinone reductase (NQO-1), a detoxication enzyme, as well as the cellular glutathione content. We conclude that DMF or SP simultaneously can (1) reduce mediators of inflammation and (2) enhance detoxication enzymes in LPS stimulated co-cultures of astroglial and microglial cells. This double-sided effect could potentially be of therapeutic interest.
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PMID:Detoxication enzyme inducers modify cytokine production in rat mixed glial cells. 1599 52

Poly(ADP-ribose) polymerase-1 (PARP-1) is involved in DNA repair, but its overactivation can induce cell death. Our aim was to investigate the role of PARP-1 in activation of programmed cell death processes in the brain during systemic inflammation. Our data indicated that lipopolysaccharide (1mg/kgb.w., i.p.)-evoked systemic inflammation enhanced PARP-1 activity in the mouse brain, leading to the lowering of beta-NAD(+) concentration, to translocation of apoptosis inducing factor from mitochondria to the nucleus, and to enhanced lipid peroxidation. Inhibitor of PARP-1, 3-aminobenzamide (30 mg/kgb.w., i.p.), protected the brain against prooxidative and cell death processes, suggesting involvement of PARP-1 in systemic inflammation-related processes in the brain.
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PMID:Poly(ADP-ribose) polymerase-1 inhibition protects the brain against systemic inflammation. 1690 42

The mortality rate for septic patients with acute renal failure is extremely high. Since sepsis is often caused by lipopolysaccharide (LPS), a model of LPS challenge was used to study the development of kidney injury. Intravital video microscopy was utilized to investigate renal peritubular capillary blood flow in anesthetized male C57BL/6 mice at 0, 2, 6, 10, 18, 24, 36, and 48 h after LPS administration (10 mg/kg ip). As early as 2 h, capillary perfusion was dramatically compromised. Vessels with continuous flow were decreased from 89 +/- 4% in saline controls to 57 +/- 5% in LPS-treated mice (P < 0.01), and vessels with intermittent flow were increased from 6 +/- 2% to 31 +/- 5% (P < 0.01). At 2 h, mRNA for intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 were elevated 50- and 27-fold, respectively, suggesting that vascular inflammation is an early event that may contribute to capillary dysfunction. By 10 h, vessels with no flow increased from 5 +/- 2% in saline controls to 19 +/- 3% in LPS-treated mice (P < 0.05). By 48 h, capillary function was returning toward control levels. The decline in functional capillaries preceded the development of renal failure and was paralleled by induction of inducible nitric oxide synthase in the kidney. Using NAD(P)H autofluorescence as an indicator of cellular redox stress, we found that tubular cell stress was highly correlated with the percentage of dysfunctional capillaries (r(2) = 0.8951, P < 0.0001). These data show that peritubular capillary dysfunction is an early event that contributes to tubular stress and renal injury.
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PMID:Peritubular capillary dysfunction and renal tubular epithelial cell stress following lipopolysaccharide administration in mice. 1692 42

Lipopolysaccharide, the main component of the cell wall of Gram-negative bacteria, is known to activate microglial cells following its interaction with the CD14/Toll-like receptor complex (TLR-4). The activation pathway triggered by lipopolysaccharide in microglia involves enhanced basal levels of intracellular calcium ([Ca2+]i) and terminates with increased generation of cytokines/chemokines and nitric oxide. Here we demonstrate that in lipopolysaccharide-stimulated murine N9 microglial cells, cyclic ADP-ribose, a universal and potent Ca2+ mobiliser generated from NAD+ by ADP-ribosyl cyclases (ADPRC), behaves as a second messenger in the cell activation pathway. Lipopolysaccharide induced phosphorylation, mediated by multiple protein kinases, of the mammalian ADPRC CD38, which resulted in significantly enhanced ADPRC activity and in a 1.7-fold increase in the concentration of intracellular cyclic ADP-ribose. This event was paralleled by doubling of the basal [Ca2+]i levels, which was largely prevented by the cyclic ADP-ribose antagonists 8-Br-cyclic ADP-ribose and ryanodine (by 75% and 88%, respectively). Both antagonists inhibited, although incompletely, functional events downstream of the lipopolysaccharide-induced microglia-activating pathway, i.e. expression of inducible nitric oxide synthase, overproduction and release of nitric oxide and of tumor necrosis factor alpha. The identification of cyclic ADP-ribose as a key signal metabolite in the complex cascade of events triggered by lipopolysaccharide and eventually leading to enhanced generation of pro-inflammatory molecules may suggest a new therapeutic target for treatment of neurodegenerative diseases related to microglia activation.
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PMID:Cyclic ADP-ribose is a second messenger in the lipopolysaccharide-stimulated activation of murine N9 microglial cell line. 1698 44

The mortality rate for septic patients with acute renal failure is approximately doubled compared with patients with sepsis alone. Unfortunately, the treatment for sepsis-induced renal failure has advanced little during the last several decades. Because sepsis is often caused by lipopolysaccharide (LPS), a mouse model of LPS challenge was used to study the development of kidney injury. We hypothesized that inducible nitric-oxide synthase (iNOS)-catalyzed nitric oxide production and that generation of reactive nitrogen species (RNS) might play a role in the microcirculatory defect and resulting tubular injury associated with LPS administration. Fluorescent intravital videomicroscopy was used to assess renal peritubular capillary perfusion and document RNS generation by renal tubules in real time. As early as 6 h after LPS administration (10 mg/kg i.p.), RNS generation (rhodamine fluorescence), redox stress [NAD(P)H autofluorescence], and the percentage of capillaries without flow were each significantly increased compared with saline-treated mice (p < 0.05). The generation of RNS was supported by the detection of nitrotyrosine-protein adducts in the kidney using immunohistochemistry. The iNOS inhibitor l-N(6)-(1-iminoethyl)-lysine (l-NIL; 3 mg/kg i.p.) completely blocked the increase in rhodamine fluorescence and NAD(P)H autofluorescence and prevented the capillary defects at 6 h after LPS administration. These results suggest that iNOS-derived RNS is an important contributor to the peritubular capillary perfusion defects and RNS generation that occur during sepsis and emphasize that pharmacological inhibition of iNOS may provide beneficial effects during sepsis by improving renal capillary perfusion and reducing RNS generation in the kidney.
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PMID:Effects of the inducible nitric-oxide synthase inhibitor L-N(6)-(1-iminoethyl)-lysine on microcirculation and reactive nitrogen species generation in the kidney following lipopolysaccharide administration in mice. 1720 3

Bacteria of genus Aeromonas, responsible for a variety of pathological conditions in humans and fish, are ubiquitous waterborne bacteria. Aeromonas produces several virulent factors including a complex of lipopolysaccharide and surface array protein, involved in colonization. UDP-galactose 4-epimerase (GalE) catalyzes the production of UDP-galactose, a precursor for lipopolysaccharide biosynthesis, and thus is an important drug target. GalE exhibits interspecies variation and heterogeneity at its structural and functional level and therefore, the differences between the GalE of the host and the pathogen can be exploited for drug designing. In the present study, we report biochemical and functional characterization of the recombinant GalE of Aeromonas hydrophila. Unlike GalE reported from all other species, the purified recombinant GalE of A. hydrophila was found to exist as a monomer. This is the first report of UDP-galactose 4-epimerase from any species being a monomer. The molecular mass of the 6xHis-rGalE was determined to be 38271.477 (m/z). The 6xHis-rGalE with a K(m) of 0.5 mM for UDP-galactose exhibited optimum activity at 37 degrees C and pH 8-9. Spectrofluorimetric and CD analysis confirmed that the thermal inactivation was due to structural changes and not due to the NAD-dissociation. A relatively more ordered structure of the enzyme at pH 8 and 9 as compared to that at pH 6 or 7 suggests a key role of the electrostatic interactions in maintaining its native tertiary structure.
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PMID:Biochemical and functional characterization of UDP-galactose 4-epimerase from Aeromonas hydrophila. 1755 60

The nuclear enzyme poly(ADP-ribose) polymerase-1 (PARP-1) which was initially known for its role in the repair of oxidative stress-induced DNA damage, has also been reported to play a mediating role in the inflammatory response. Studies with PARP-1 knockout models have shown that PARP-1 is a co-activator of Nuclear Factor-kappa B (NF-kappaB), although this appears not to require its enzyme activity. In addition, drug-induced inhibition of the enzyme activity of PARP-1 was observed to reduce the production of pro-inflammatory mediators. In this study, the flavonoid compound flavone was demonstrated to significantly inhibit the enzyme activity of PARP-1. Further evaluation of flavone in N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-treated human pulmonary epithelial and vascular endothelial cells revealed that both the decrease in NAD(+) levels, as well as the formation of PAR-polymers was dose-dependently attenuated by flavone. In addition, flavone was found to reduce the lipopolysaccharide (LPS)-induced interleukin (IL)-8 production in pulmonary epithelial cells, which was confirmed by transcription analysis. Furthermore, the transcription Inhibitor kappa B alpha (of IkappaBalpha) was significantly increased by flavone. The results of the present study indicate that the flavonoid flavone could be a potential candidate for application in treatment of chronic inflammatory diseases. PARP-1 inhibition could have beneficial effects in such diseases as Chronic Obstructive Pulmonary Disease (COPD) and diabetes, by preservation of cellular NAD(+) levels and attenuating inflammatory conditions.
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PMID:Flavone as PARP-1 inhibitor: its effect on lipopolysaccharide induced gene-expression. 1764 14

The pathogenic bacteria Bordetella parapertussis and Bordetella bronchiseptica express a lipopolysaccharide O antigen containing a polymer of 2,3-diacetamido-2,3-dideoxy-l-galacturonic acid. The O-antigen cluster contains three neighbouring genes that encode proteins belonging to the short-chain dehydrogenase/reductase (SDR) family, wbmF, wbmG and wbmH, and we aimed to elucidate their individual functions. Mutation and complementation implicate each gene in O-antigen expression but, as their putative sugar nucleotide substrates are not currently available, biochemical characterisation of WbmF, WbmG and WbmH is impractical at the present time. SDR family members catalyse a wide range of chemical reactions including oxidation, reduction and epimerisation. Because they typically share low sequence conservation, however, catalytic function cannot be predicted from sequence analysis alone. In this context, structural characterisation of the native proteins, co-crystals and small-molecule soaks enables differentiation of the functions of WbmF, WbmG and WbmH. These proteins exhibit typical SDR architecture and coordinate NAD. In the substrate-binding domain, all three enzymes bind uridyl nucleotides. WbmG contains a typical SDR catalytic TYK triad, which is required for oxidoreductase function, but the active site is devoid of additional acid-base functionality. Similarly, WbmH possesses a TYK triad, but an otherwise feature-poor active site. Consequently, 3,5-epimerase function can probably be ruled out for these enzymes. The WbmF active site contains conserved 3,5-epimerase features, namely, a positionally conserved cysteine (Cys133) and basic side chain (His90 or Asn213), but lacks the serine/threonine component of the SDR triad and therefore may not act as an oxidoreductase. The data suggest a pathway for synthesis of the O-antigen precursor UDP-2,3-diacetamido-2,3-dideoxy-l-galacturonic acid and illustrate the usefulness of structural data in predicting protein function.
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PMID:Predicting protein function from structure--the roles of short-chain dehydrogenase/reductase enzymes in Bordetella O-antigen biosynthesis. 1795 Jul 51

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