Modulation of the immune response by a synthetic adjuvant and analogs.
(9/386)
N-Acetylmuramyl-L-alanyl-D-isoglutamine increases the humoral immune response of mice when given in aqueous media instead of the usual water-in-oil emulsions. Moreover, this compound is adjuvant active even by the oral route. In view of studying the relation between chemical structure and biological activity, several synthetic analogs were tested. The immune response could be modulated according to chemical modifications, and the synthetic analog with D- in place of L-alanine was shown to inhibit the immune response. (+info)
Characterization of a novel endopolygalacturonase from Aspergillus niger with unique kinetic properties.
(10/386)
We isolated and characterized a new type of endopolygalacturonase (PG)-encoding gene, pgaD, from Aspergillus niger. The primary structure of PGD differs from that of other A. niger PGs by a 136 amino acid residues long N-terminal extension. Biochemical analysis demonstrated extreme processive behavior of the enzyme on oligomers longer than five galacturonate units. Furthermore, PGD is the only A. niger PG capable of hydrolyzing di-galacturonate. It is tentatively concluded that the enzyme is composed of four subsites. The physiological role of PGD is discussed. (+info)
Cloning and expression of the human N-acetylneuraminic acid phosphate synthase gene with 2-keto-3-deoxy-D-glycero- D-galacto-nononic acid biosynthetic ability.
(11/386)
Sialic acids participate in many important biological recognition events, yet eukaryotic sialic acid biosynthetic genes are not well characterized. In this study, we have identified a novel human gene based on homology to the Escherichia coli sialic acid synthase gene (neuB). The human gene is ubiquitously expressed and encodes a 40-kDa enzyme. The gene partially restores sialic acid synthase activity in a neuB-negative mutant of E. coli and results in N-acetylneuraminic acid (Neu5Ac) and 2-keto-3-deoxy-D-glycero-D-galacto-nononic acid (KDN) production in insect cells upon recombinant baculovirus infection. In vitro the human enzyme uses N-acetylmannosamine 6-phosphate and mannose 6-phosphate as substrates to generate phosphorylated forms of Neu5Ac and KDN, respectively, but exhibits much higher activity toward the Neu5Ac phosphate product. (+info)
A common regulator for the operons encoding the enzymes involved in D-galactarate, D-glucarate, and D-glycerate utilization in Escherichia coli.
(12/386)
Genes for D-galactarate (gar) and D-glucarate (gud) metabolism in Escherichia coli are organized in three transcriptional units: garD, garPLRK, and gudPD. Two observations suggested a common regulator for the three operons. (i) Their expression was triggered by D-galactarate, D-glucarate, and D-glycerate. (ii) Metabolism of the three compounds was impaired by a single Tn5 insertion mapped in the yaeG gene (proposed name, sdaR), outside the D-galactarate and D-glucarate systems. Expression of the sdaR gene is autogenously regulated. (+info)
Crystal structures of the metal-dependent 2-dehydro-3-deoxy-galactarate aldolase suggest a novel reaction mechanism.
(13/386)
Carbon-carbon bond formation is an essential reaction in organic chemistry and the use of aldolase enzymes for the stereochemical control of such reactions is an attractive alternative to conventional chemical methods. Here we describe the crystal structures of a novel class II enzyme, 2-dehydro-3-deoxy-galactarate (DDG) aldolase from Escherichia coli, in the presence and absence of substrate. The crystal structure was determined by locating only four Se sites to obtain phases for 506 protein residues. The protomer displays a modified (alpha/beta)(8) barrel fold, in which the eighth alpha-helix points away from the beta-barrel instead of packing against it. Analysis of the DDG aldolase crystal structures suggests a novel aldolase mechanism in which a phosphate anion accepts the proton from the methyl group of pyruvate. (+info)
Structural analysis of the lipopolysaccharide from Chlamydophila psittaci strain 6BC.
(14/386)
The lipopolysaccaride of Chlamydophila psittaci 6BC was isolated from tissue culture-grown elementary bodies using a modified phenol/water procedure followed by extraction with phenol/chloroform/light petroleum. Compositional analyses indicated the presence of 3-deoxy-Dmanno-oct-2-ulosonic acid, GlcN, organic bound phosphate and fatty acids in a molar ratio of approximately 3. 3 : 2 : 1.8 : 4.6. Deacylated lipopolysaccharide was obtained after successive microscale treatment with hydrazine and potassium hydroxide, and was then separated by high performance anion-exchange chromatography into two major fractions, the structures of which were determined by 600 MHz NMR spectroscopy as alpha-Kdo-(2-->8)-alpha-Kdo-(2-->4)-alpha-Kdo-(2-->6)-beta-D-GlcpN -(1 -->6)-alpha-D-GlcpN 1,4'-bisphosphate and alpha-Kdo-(2-->4)-[alpha-Kdo-(2-->8)]-alpha-Kdo-(2-->4)-alpha-Kdo-(2- ->6)-beta-D-GlcpN-(1-->6)-alpha-D-GlcpN 1,4'-bisphosphate. The distribution of fatty acids in lipid A was determined by compositional analyses and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry experiments on lipid A and de-O-acylated lipid A. It was shown that the carbohydrate backbone of lipid A is replaced by a complex mixture of fatty acids, including long-chain and branched (R)-configured 3-hydroxy fatty acids, the latter being exclusively present in an amide linkage. (+info)
Ca2+-induced phosphoethanolamine transfer to the outer 3-deoxy-D-manno-octulosonic acid moiety of Escherichia coli lipopolysaccharide. A novel membrane enzyme dependent upon phosphatidylethanolamine.
(15/386)
Certain strains of Escherichia coli and Salmonella contain lipopolysaccharide (LPS) modified with a phosphoethanolamine (pEtN) group at position 7 of the outer 3-deoxy-d-manno-octulosonic acid (Kdo) residue. Using the heptose-deficient E. coli mutant WBB06 (Brabetz, W., Muller-Loennies, S., Holst, O., and Brade, H. (1997) Eur. J. Biochem. 247, 716-724), we now demonstrate that the critical parameter determining the presence or absence of pEtN is the concentration of CaCl(2) in the medium. As judged by mass spectrometry, half the LPS in WBB06, grown on nutrient broth with 5 mm CaCl(2), is derivatized with a pEtN group, whereas LPS from WBB06 grown without supplemental CaCl(2) is not. Membranes from E. coli WBB06 or wild-type W3110 grown on 5-50 mm CaCl(2) contain a novel pEtN transferase that uses the precursor Kdo(2)-[4'-(32)P]lipid IV(A) as an acceptor. Transferase is not present in membranes of E. coli grown with 5 mm MgCl(2), BaCl(2), or ZnCl(2). Hydrolysis of the in vitro reaction product, pEtN-Kdo(2)-[4'-(32)P]lipid IV(A), at pH 4.5 shows that the pEtN substituent is located on the outer Kdo moiety. Membranes from an E. coli pss knockout mutant grown on 50 mm CaCl(2), which lack phosphatidylethanolamine, do not contain measurable transferase activity unless exogenous phosphatidylethanolamine is added back to the assay system. The induction of the pEtN transferase by 5-50 mm CaCl(2) suggests possible role(s) in establishing transformation competence or resisting environmental stress, and represents the first example of a regulated covalent modification of the inner core of E. coli LPS. (+info)
The effect of vincristine on the biodistribution of technetium-99m DTPA, GHA, and DMSA in Balb/c female mice.
(16/386)
OBJECTIVE: Vincristine has been widely used in various chemotherapeutic protocols in oncology. The purpose of this study was to evaluate the effect of vincristine on the biodistribution of 99mTc-DMSA, 99mTc-GHA, and 99mTc-DTPA in Balb/c female mice. METHODS: Vincristine (0.03 mg, 0.3 mL) was injected into female isogenic Balb/c mice (n = 15), in 3 doses over an interval of 96 h. The 99mTc-DMSA, 99mTc-GHA, or 99mTc-DTPA (7.4 MBq) was administered after the last dose of vincristine. After 0.5 h the animals were killed rapidly. The organs (pancreas, thyroid, brain, thymus, ovary, uterus, spleen, kidney, heart, stomach, lung, liver, bone, and lymph nodes) were isolated and the radioactivity in each organ was counted in a NaI(Tl) well counter. The percentage of radioactivity (%) in each was calculated and compared with the control group. Statistical analysis was performed by Wilcoxon test (P < 0.05). RESULTS: The percentage of 99mTc-DMSA was increased in the lung, pancreas, heart, thyroid, brain, bone, and lymph nodes (inguinal and mesenteric). The percentage of 99mTc-GHA was decreased in the uterus, ovary, spleen, thymus, lymph nodes (inguinal and mesenteric), kidney, and heart. The percentage of 99mTc-DTPAwas increased in thymus, lymph nodes (inguinal and mesenteric), ovary, uterus, spleen, kidney, heart, stomach, lung, liver, and bone. CONCLUSION: The results could be explained by the metabolization, toxic effect, therapeutic, or immunosupressive action of the studied chemotherapeutic drug. (+info)