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PubMed1996

Structure determination of a novel uronic acid residue isolated from the exopolysaccharide produced by a bacterium originating from deep sea hydrothermal vents.

The exopolysaccharide produced by the bacterium Alteromonas sp. strain 1644 originating from deep sea hydrothermal vents was shown to contain a novel glucuronic acid derivatives: 3-O-[(R)-1-carboxyethyl]-D-glucuronic acid. The structure of this compound was established on the basis of mass spectrometric data, methylation analysis, preparation of derivatives, and chemical synthesis of references compounds.

Archaea↗
PubMed1968

The tissue content and turnover rates of intermediates in the biosynthesis of glycosaminoglycans in young rat skin.

1. The tissue contents of hexose monophosphate, N-acetylglucosamine 6-phosphate, UDP-glucose, UDP-galactose, UDP-N-acetylglucosamine, UDP-N-acetylgalactosamine and UDP-glucuronic acid were determined in the skin of young rats less than 1 day post partum. Tissue-space determinations were used to calculate their average cellular concentrations. 2. The incorporation of [U-(14)C]-glucose into the intermediates was recorded with time and their rates of turnover were calculated. The results demonstrated product-precursor relationships along the pathway of hexosamine synthesis and that of hexuronic acid synthesis. The rates of synthesis of UDP-N-acetylhexosamine and UDP-glucuronic acid were 1.5+/-0.3 and 0.24+/-0.03mmumoles/min./g. of tissue respectively. These results indicated the average turnover time of the total tissue glycosaminoglycans to be about 5 days.

Animals↗
PubMed1985

Distribution of glucuronic and iduronic acid units in heparin chains.

The distribution of glucuronic and iduronic acid within the chains of anticoagulantly active and inactive beef lung heparin was investigated. A fraction with an average molecular weight of 19,500 was isolated from the heterodisperse mixture and then separated into active and inactive components by affinity chromatography. Each sample was linked through its reducing terminus to tyramine, reduced with sodium borotritide, and bound covalently to Sepharose via an azo bridge. The bound reduced heparin was treated with a limited amount of HNO2 and the degraded fragments were removed. The sections of the chain contiguous with the original reducing terminus were then detached from the insoluble matrix by reaction with sodium dithionite. The recovered polysaccharide was fractionated according to size on Sephadex G-200 and the amount of each uronic acid in the individual fractions was determined. Inactive heparin showed a constant percentage of glucuronic acid in all fragments, i.e. about 8.9% of the total uronic acid. With active heparin the percentage of glucuronic acid increased with the distance from the reducing terminus of the polysaccharide chain, ranging from 9.5 to 20% of the uronic acids. These results suggest that the biosynthesis of active heparin involves unique reactions or specific processing of the macromolecule.

Animals↗
PubMed2003

Metabolic fate of pitavastatin, a new inhibitor of HMG-CoA reductase: similarities and difference in the metabolism of pitavastatin in monkeys and humans.

1. To elucidate any potential species differences, the in vitro metabolism of pitavastatin and its lactone was studied with hepatic and renal microsomes from rats, dogs, rabbits, monkeys and humans. 2. With the addition of UDP-glucuronic acid to hepatic microsomes, pitavastatin lactone was identified as the main metabolite in several animals, including humans. 3. Metabolic clearances of pitavastatin and its lactone in monkey hepatic microsome were much greater than in humans. 4. M4, a metabolite of pitavastatin with a 3-dehydroxy structure, was converted to its lactone form in monkey hepatic microsomes in the presence of UDP-glucuronic acid as well as to pitavastatin. These results implied that lactonization is a common pathway for drugs such as 5-hydroxy pentanoic acid derivatives. 5. The acid forms were metabolized to their lactone forms because of their structural characteristics. 6. UDP-glucuronosyltransferase is the key enzyme responsible for the lactonization of pitavastatin, and overall metabolism is different compared with humans owing to the extensive oxidative metabolism of pitavastatin and its lactone in monkey.

Animals↗
PubMed1988

Effect of butylated hydroxyanisole on hepatic glucuronidation and biliary excretion of drugs in mice.

Inhibition of glucuronidation by depletion of UDP-glucuronic acid from liver impairs the hepatobiliary transport of glucuronidated xenobiotics. However, it is not known if enhancement of hepatic glucuronidation increases the biliary excretion of these compounds. Therefore, the effect of treatment with butylated hydroxyanisole (BHA), which increases hepatic glucuronidation capacity, on the biliary excretion of compounds undergoing glucuronidation was studied in mice. BHA-feeding (1% for 10 days) increased hepatic UDP-glucuronic acid content by 240% and enhanced hepatic UDP-glucuronosyltransferase activities (expressed per kg body weight) toward valproic acid, phenolphthalein, iopanoic acid and bilirubin 220, 180, 120 and 60%, respectively. BHA treatment did not influence the biliary excretion of unmetabolized cholephils, phenol-3,6-dibromphthalein disulphonate and phenolphthalein glucuronide, but enhanced that of phenolphthalein (+108%), iopanoic acid (+63%) and bilirubin (+33%) as glucuronides. However, these increases were apparent only in the initial phase of excretion. In contrast, BHA markedly decreased (-43%) the biliary excretion of valproic acid glucuronides. Simultaneously, BHA increased the urinary excretion of the glucuronides of phenolphthalein (+48%), iopanoic acid (+450%) and valproic acid (+150%). A shift in the distribution of iopanoic acid and valproic acid and metabolites from liver to kidney was also apparent in BHA-fed mice. Thus, enhanced glucuronidation does not facilitate the biliary excretion of all glucuronidated compounds and only transiently increases others. It is likely that this phenomenon is the result of the glucuronides readily entering the plasma and being excreted by the kidney.

Animals↗
PubMed1979

Urinary metabolite of 1-(2,4,6-trichlorophenyl)-3,3-dimethyltriazene with an intact diazoamino structure.

The tumour-inhibiting substance 1-(2,4,6-trichlorophenyl)-3,3-dimethyltriazene is metabolised in rats to the corresponding substituted 1-O-(triazenyl-methyl) glucuronic acid. The urinary metabolite was purified by ion exchange chromatography and gel filtration, and isolated from the enriched fractions by freeze-drying. Cold acid cleavage into the 2,4,6-trichlorobenzene-diazonium cation and hydrolysis to glucuronic acid and formaldehyde indicated the presence of an O-glycosidic bond through an enzymically-introduced hydroxymethyl oxygen. This novel type of glucuronoside structure was established by chemical evidence, and confirmed by NMR and field-desorption mass spectrometry. It is conceivable that this metabolite represents a stabilised carrier form of the biologically-active triazene that transports the methylating agent from its site of formation to its ultimate target.

Animals↗
PubMed1987

Biochemistry of hyaluronan.

Hyaluronan (hyaluronic acid) is a linear polysaccharide formed from disaccharide units containing N-acetylglucosamine and glucuronic acid. It is ubiquitously distributed in the organism but is found in the highest concentrations in soft connective tissues. The molecular weight of hyaluronan is usually in the order of 10(6) to 10(7). Due to hydrogen bonding, the chain is rather stiff and the molecule behaves in solution as an extended, randomly kinked coil. Molecules of hyaluronan start to entangle already at concentrations of less than 1 g/l and form a continuous polymer network. Some of the functions of the polysaccharide have been connected with the unique physical chemical characteristics of the network such as its rheological properties, flow resistance, osmotic pressure, exclusion properties and filter effect. Hyaluronan is synthesized in the cell membrane by adding monosaccharides to the reducing end of the chain. The precursors are UDP-glucuronic acid and UDP-N-acetylglucosamine. The polysaccharide grows out from the cell surface and it can be shown that fibroblasts, for example, surround themselves with a coat of hyaluronan. The rate of biosynthesis is regulated by various factors, such as growth factors, hormones, inflammatory mediators, etc. The responsible enzyme, hyaluronan synthase, is a phosphoprotein and the regulation of the synthetic rate is apparently via phosphorylation. The hyaluronan is at least partly carried by lymph flow from the tissues. Part of the material is taken up and degraded in the lymph nodes. Another part is carried to the general circulation and taken up in the endothelial cells in the liver sinusoids. These cells have specific receptors for hyaluronan, which also recognize chondroitin sulphate. The uptake in the liver of high-molecular weight hyaluronan is very efficient and its normal half-life in serum is only in the order of 2 to 5 min. The polysaccharide is rapidly degraded in the lysosomes to low-molecular weight products, lactate and acetate. The total turnover of hyaluronan in serum is in the order of 10-100 mg/24 h. The normal concentration of hyaluronan in serum is less than 100 micrograms/l with a mean of 30-40 micrograms/l. High serum levels have been noted in liver cirrhosis (impaired uptake in the liver) and rheumatoid arthritis (increased synthesis in the tissues). Hyaluronan has been shown to interact specifically with certain proteins and cell surfaces. It binds to proteoglycans in cartilage and other tissues and fills an important structural role in the organization of the extra-cellular matrix.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Insect glycolipids.

Systematic elucidations of the chemical structures of glycosphingolipids from members of the phyla Arthropoda (class:insecta) of the Protostomia have shown several characteristic differences to those of the Deuterostomia, e.g., the Vertebrata. The ceramide constituents of the arthropod sphingolipids are C14:1- and C16:1-sphingoid and a majority of saturated C18-, C20-, C22- and C24-fatty acids. The GSL of the dipteran insects, L. caesar and C. vicina, consist of a series of homologous compounds of increasing sugar chain length. The carbohydrate moieties of these arthropod GSL are all derived from one unique neutral sugar core sequence, the arthro-series. The longest member known, an arthrononaosylceramide has the structure Gal beta,3GalNAc beta,3GlcNAc beta,3Gal beta,3GalNAc alpha,4GalNAc beta,4GlcNAc beta,3Man beta,4Glc beta Cer. Three pentahexosylceramides have been characterized that differ in their nonreducing terminus, i.e., IV4GalNAc alpha-Ap4Cer, IV3Gal alpha-Ap4Cer and IV3Gal beta-Ap4Cer. A large repertoire of structural variations of the arthro-series GSL is created by two types of derivatisations of the neutral carbohydrate core: addition of a zwitterionic 2-aminoethylphosphate group in phosphodiester linkage to the 6-position of the III-N-acetylglucosamine of the arthrotriaosylceramide core and/or substitution of a terminal galactose in 3-position by a glucuronic acid residue. The latter acidic arthro-series GSL were given the name arthrosides. Preliminary results have indicated that the blowfly GSL component distribution is strongly organ specific. GSL of various larval organs are distinguished by the length of their neutral core carbohydrate chain, as well as, the degree of PEtn- and GlcA-substitutions. Normal human sera contain antibodies that recognize epitopes on arthro-series GSL. Thereby, sites of the neutral carbohydrate chain, as well as, the zwitterionic and acidic epitopes are involved in the immune recognition. In a pathological condition, a M-protein of patients with autoallergic demyelinating peripheral neuropathy was found to react strongly with a glucuronic acid-containing molecular structure on arthrosides. Some indication was obtained for a possible functional role of glucuronic acid in dipteran-cell adhesion by using a mouse monoclonal antibody, mAb CAF-I. This antibody, directed against an arthroside epitope involving glucuronic acid, could induce an in vitro detachment of insect cells from one another or from their substratum. Obviously, present research on the GSL of insects is only at an early stage. Nevertheless, from the results available so far it was become increasingly apparent that a new chapter in our knowledge of GSL structures has been opened.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1982

Mechanisms of organic acid and monosaccharide transport in the kidney of the brush-tailed possum, Trichosurus vulpecula.

The mechanisms of organic acid and monosaccharide transport in the kidney of T. vulpecula were investigated using the renal cortical slice preparation. The kinetics, the sensitivity to inhibitors of metabolism and sodium transport, and the specificity of the concentrative uptake of p-amino-hippurate and alpha-methyl-D-glucoside were examined and compared with published results from studies in eutherian mammals. Some minor differences between metatherians and eutherians were noted with regard to the specificities of the renal slice uptake systems. Penicillin G, a competitor of organic acid transport in eutherian kidneys, did not interact with the marsupial uptake system, and sodium acetate, which stimulates transport in other mammals, inhibited p-aminohippurate uptake in the slice of the possum kidney. 2-Deoxy-D-glucose, which interacts with the phlorizin-sensitive monosaccharide transport system in the dog, rat and rabbit kidney, had no effect on alpha-methyl-D-glucoside uptake in the possum, and the magnitude of the interaction of D-fructose resembled that reported in the dog and rat but was greater than the inhibition reported in the rabbit. D-Glucuronic acid and D-glucuronic acid lactone inhibited alpha-methyl-D-glucoside uptake in the possum but had no effect on uptake in rat renal slices. In consideration of the reported variability of these parameters between different classes of eutherians, it was concluded that the primary mechanisms involved in organic solute transport by the proximal nephron of metatherians and eutherians were not significantly different.

Aminohippuric Acids↗
PubMed1978

Metabolism of myo-Inositol by Germinating Lilium longiflorum Pollen.

Lilium Iongiflorum pollen tubes absorbed myo-[2-(3)H]inositol produced labeled metabolites which were separated into acid-soluble and -insoluble fractions. The soluble fraction contained labeled myo-inositol, d-glucuronic acid, myo-inositol 1-phosphate, and at least three other unidentified compounds. The acid-insoluble fraction contained considerable chloroformsoluble radioactivity and a labeled residue. Labeled myo-inositol was also absorbed by germinating pollen prior to the time of pollen tube initiation; however, there was a marked reduction in amounts of myo-inositol 1-phosphate and glucuronic acid produced by this pollen in comparison with growing pollen tubes.

Journal Article↗
PubMed1997

Assay of R-apomorphine, S-apomorphine, apocodeine, isoapocodeine and their glucuronide and sulfate conjugates in plasma and urine of patients with Parkinson's disease.

Analytical methods are described for the selective, rapid and sensitive determination of R- and S-apomorphine, apocodeine and isoapocodeine and the glucuronic acid and sulfate conjugates in plasma and urine. The methods involve liquid-liquid extraction followed by high-performance liquid chromatography with electrochemical detection. The glucuronide and sulfate conjugates are determined after enzymatic hydrolysis. For the assay of R- and S-apomorphine a 10 microm Chiralcel OD-R column is used and the voltage of the detector is set at 0.7 V. The mobile phase is a mixture of aqueous phase (pH 4.0)-acetonitrile (65:35, v/v). At a flow-rate of 0.9 ml min(-1) the total run time is ca. 15 min. The detection limits are 0.3 and 0.6 ng ml(-1) for R- and S- apomorphine, respectively (signal-to-noise ratio 3). The intra- and inter-assay variations are <5% in the concentration range of 2.5-25 ng ml(-1) for plasma samples, and <4% in the concentration range of 40-400 ng ml(-1) for urine samples. For the assay of apomorphine, apocodeine and isoapocodeine, a 5 microm C18 column was used and the voltage of the detector set at 0.825 V. Ion-pairing chromatography was used. The mobile phase is a mixture of aqueous phase (pH 3.0)-acetonitrile (75:25, v/v). At a flow-rate of 0.8 ml min(-1) the total run time is ca. 14 min. The detection limits of this assay are 1.0 ng ml(-1) for apomorphine and 2.5 ng ml(-1) for both apocodeine and isoapocodeine (signal-to-noise ratio 3). The inter-assay variations are 5% in the concentration range of 5-40 ng ml(-1) for plasma samples and 7% in the concentration range of 50-500 ng ml(-1) for urine samples. The glucuronic acid and sulfate conjugates of the various compounds are hydrolysed by incubation of the samples with beta-glucuronidase and sulfatase type H-1, respectively. Hydrolysis was complete after 5 h of incubation. No measurable degradation of apomorphine, apocodeine and isoapocodeine occurred during the incubation. A pharmacokinetic study of apomorphine, following the intravenous infusion of 30 microg kg(-1) for 15 min in a patient with Parkinson's disease, demonstrates the utility of the methods: both the pharmacokinetic parameters of the parent drug and the appearance of apomorphine plus metabolites in urine could be determined.

Acetic Acid↗
PubMed1994

Relative influence of different disulphate disaccharide clusters on the HCII-mediated inhibition of thrombin by dermatan sulphates of different origins.

Besides the major monosulphated disaccharide sequences (IdoA-GalNAc4SO3), dermatan sulphates (DS) contain the oversulphated sequences (IdoA2SO3-GalNAc4SO3) and (IdoA-GalNAc4, 6SO3), the concentration of which is correlated with the HCII-mediated inhibition of thrombin by DS. The effect of the chemical removal of the sulphate groups on the HCII-mediated activity was studied. The base-catalyzed sulphate group displacement from IdoA2SO3 residues, leading to formation of the epoxyde aGulA, is a 1st order reaction. When the content of sequences (IdoA-GalNAc4, 6SO3) is higher than that of sequences (IdoA2SO3-GalNAc4SO3), removal of the sulphate groups from Ido2SO3 reduces the HCII activity less than when the latter sequences prevail. (IdoA-GalNAc4, 6SO3) cooperates with (IdoA2SO3-GalNAc4SO3) in the activation of the HCII. Also the removal of 6-SO3- groups from GalNAc4, 6SO3, in absence of IdoA2SO3-GalNAc4SO3, considerably reduces the activity. A low molecular mass natural fraction rich in IdoA2SO3 as well as glucuronic acid, having higher electrophoretic mobility than the higher molecular mass DS which contains less glucuronic acid, is remarkably active.

Animals↗
PubMed2003

Probiotic effects of beta-glucuronidase on the peach-potato aphid Myzus persicae (Aphididae).

beta-glucuronidase (GUS) is a reporter protein commonly expressed in transgenic plants allowing the visualization of the transformed individuals. In our recent work, we showed that consumption of transformed potato plants expressing this GUS enzyme improves performance of the phloem feeding aphid Myzus persicae. Those results led us to the conclusion that the expression of GUS in potato plants might be responsible for the probiotic effect measured in feeding aphids. In the present paper, artificial diets were used to provide active GUS (10 and 500 microg ml(-1)), inactivated heated GUS (500 microg ml(-1)), glucuronic acid (10, 100 and 500 microg ml(-1)), and bovine serum albumin (500 microg ml(-1)) to M. persicae. Our results reveal that these chemicals provided as food intake might influence the biological parameters of this aphid. Experiments showed a probiotic effect of 500 microg ml(-1) GUS diet, resulting in reduced larval mortality, and increased adult reproduction period and fecundity, which led to an increased population growth potential (r(m)=0.17+/-0.01 versus r(m)=0.12+/-0.03 for aphids fed on control diet). A lower amount of added GUS led to fewer variations, biological parameters being only slightly altered (r(m)=0.14+/-0.03). Statistically similar alterations of the biological parameters were obtained when comparing aphids fed on the diet added with inactivated GUS or the non-structural bovine serum albumin protein (r(m)=0.15+/-0.02 and 0.14+/-0.03, respectively). Feeding assays conducted with glucuronic acid supplemented diets enhanced longevity and nymph production of the adult aphids and reduced larval mortality, resulting in r(m)=0.15+/-0.02 for the highest dose (500 microg ml(-1)). Although 100 microg ml(-1) glucuronate diet did not induce any effect on M. persicae (r(m)=0.12+/-0.03), aphids fed on 10 microg ml(-1) glucuronate diet exhibited unexpected reduced demographic parameters (r(m)=0.10+/-0.03). Immuno-histological analysis showed GUS labeling along the whole digestive epithelium of adults and in various tissues including embryos and bacteriocytes. These results suggest that GUS crosses through the digestive tract. Western blots performed with protein extracts of transformed potato plants expressing the gus gene showed a unique band of molecular weight 76 kDa. On the contrary, in extracts from aphids fed on transgenic potato plants or bred on GUS 500 microg ml(-1) artificial diet, several proteins of lower molecular weight were hybridized, revealing proteolysis of ingested GUS. It is concluded that GUS protein, and more precisely GUS activity, is responsible for the probiotic effects on aphid feeding. The possible pathways of induction of such physiological alterations by GUS are discussed.

Animal Feed↗
PubMed1990

Chromotropic character of bacterial acidic polysaccharides: Part III--Interaction of cationic dye pinacyanol chloride with Klebsiella K15 capsular polysaccharide.

Interaction of cationic dye pinacyanol chloride with the acidic capsular polysaccharide isolated from Klebsiella serotype K15 has been investigated by spectral measurements. Klebsiella K15 polysaccharide consists of hexasaccharide repeating units containing one residue each of glucuronic acid and glucose, and four residues of galactose. Glucuronic acid acts as the potential anionic site and the biopolymer interacts with the dye cations. It induces metachromasy in the dye and a blue shift of about 100 nm is observed in the visible absorption spectrum of the dye. Spectral measurements have been carried out at different polymer/dye molar ratios. Stoichiometry of polymer and dye in the polyanion-dye compound (1:1) indicates that every potential anionic site of the polyanion is associated with the dye cation, and stacking conformation is thus suggested. Effect of different non-aqueous solvents in reversing metachromasy has also been studied. Interaction studies exhibit chromotropic character of the biopolymer.

Bacterial Capsules↗
PubMed2003

In vitro polymerization of heparan sulfate backbone by the EXT proteins.

Multiple exosotoses is a dominantly inherited bone disorder caused by defects in EXT1 and EXT2, genes encoding glycosyltransferases involved in heparan sulfate chain elongation. Heparan sulfate polymerization occurs by the alternating addition of glucuronic acid and N-acetylglucosamine units to the nonreducing end of the polysaccharide. EXT1 and EXT2 are suggested to be dual glucuronyl/N-acetylglucosaminyltransferases, and a heterooligomeric complex of EXT1 and EXT2 (EXT1/2) is considered to be the biological functional polymerization unit. Here, we have investigated the in vitro polymerization capacities of recombinant soluble EXT1, EXT2, and EXT1/2 complex on exogenous oligosaccharide acceptors derived from Escherichia coli K5 capsular polysaccharide. Incubations of recombinant EXT1 or EXT1/2 complex with 3H-labeled oligosaccharide acceptors and the appropriate nucleotide sugars resulted in conversion of the acceptors to higher molecular weight compounds but with different efficacies for EXT1 and EXT1/2. In contrast, incubations with recombinant EXT2 resulted in the addition of a single glucuronic acid but no further polymerization. These results indicate that EXT1 alone and the EXT1/2 heterocomplex can act as heparan sulfate polymerases in vitro without the addition of additional auxiliary proteins.

Cell Line↗
PubMed1991

In vitro enantioselective glucuronidation of fenoprofen.

The diastereomeric glucuronic acid conjugates are major metabolites of the nonsteroidal anti-inflammatory drug fenoprofen (FEN). Glucuronidation of FEN enantiomers was investigated with liver microsomal preparations from different species (sheep, rabbit, rat and human). The formed R- and S-FEN conjugates can be separated and quantitated directly on a C18 reversed-phase HPLC column using a mixture of acetonitrile and tetrabutylammonium sulfate buffer, pH 2.5, as mobile phase. Applying this analytical procedure, it is possible to characterize enantioselective glucuronidation of FEN. For in vitro procedures, rates of glucuronide formation are substrate (FEN) and cosubstrate (UDP glucuronic acid, UDPGA) dependent with initial rates of glucuronide formation being higher for R- than for S-FEN. The R/S ratio of the formed products was independent of UDPGA (2.5-15 mmol/l) and substrate concentrations greater than or equal to 0.4 mmol/l. Enantioselective cleavage of the formed FEN conjugates by alkaline hydrolysis and hydrolytic enzymes (R greater than S-glucuronide) can be controlled during in vitro studies by pH adjustment and the addition of enzyme inhibitors.

Animals↗
PubMed2005

Arabidopsis fragile fiber8, which encodes a putative glucuronyltransferase, is essential for normal secondary wall synthesis.

Secondary walls in vessels and fibers of dicotyledonous plants are mainly composed of cellulose, xylan, and lignin. Although genes involved in biosynthesis of cellulose and lignin have been intensively studied, little is known about genes participating in xylan synthesis. We found that Arabidopsis thaliana fragile fiber8 (fra8) is defective in xylan synthesis. The fra8 mutation caused a dramatic reduction in fiber wall thickness and a decrease in stem strength. FRA8 was found to encode a member of glycosyltransferase family 47 and exhibits high sequence similarity to tobacco (Nicotiana plumbaginifolia) pectin glucuronyltransferase. FRA8 is expressed specifically in developing vessels and fiber cells, and FRA8 is targeted to Golgi. Comparative analyses of cell wall polysaccharide fractions from fra8 and wild-type stems showed that the xylan and cellulose contents are drastically reduced in fra8, whereas xyloglucan and pectin are elevated. Further structural analysis of cell walls revealed that although wild-type xylans contain both glucuronic acid and 4-O-methylglucuronic acid residues, xylans from fra8 retain only 4-O-methylglucuronic acid, indicating that the fra8 mutation results in a specific defect in the addition of glucuronic acid residues onto xylans. These findings suggest that FRA8 is a glucuronyltransferase involved in the biosynthesis of glucuronoxylan during secondary wall formation.

Amino Acid Sequence↗
PubMed1991

Comparison of serological and chemical characteristics of capsular polysaccharides of Cryptococcus neoformans var. neoformans serotype A and Cryptococcus albidus var. albidus.

The antigenic formula and chemical structure of capsular polysaccharide (CPS) of Cryptococcus albidus var. albidus (C. albidus) were studied in relation to those of C. neoformans var. neoformans serotype A (C. neoformans A). The results of slide agglutination tests with factor sera and reciprocal adsorption experiments showed that antigenic formula of C. albidus was the same as that of C. neoformans A. The soluble CPSs from the two species were obtained from culture supernatants by precipitation with ethanol followed by purification by chromatography on DEAE-cellulose column. The structural analyses of such CPSs from the two species showed that the antigenic CPS fractions consisted of a backbone of alpha(1-3)-linked D-mannopyranosyl residues with a single branch of beta(1-2)-xylose or glucuronic acid, and mostly with O-acetyl groups, in which side chains and O-acetyl groups were responsible for antigenic specificity. It was found that there was a minor difference between the CPS of C. neoformans A and that of C. albidus; in the former, unsubstituted mannose residues existed in a low frequency, but in the latter none. Moreover, the 1H-nuclear magnetic resonance spectra of partially hydrolyzed acidic fragments of the two CPSs indicated that two xylose side chains were present between glucuronic acid side chains. Taken together, it was suggested that these two species of C. neoformans A and C. albidus are closely related to each other in their CPSs.

Animals↗