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PubMed1976

Biosynthesis of chondroitin sulfate. Independent addition of glucuronic acid and N-acetylgalactosamine to oligosaccharides.

Pentasaccharide 6-sulfate and hexasaccharide 6-sulfate were prepared from chondroitin 6-sulfate. Each oligosaccharide was incubated with a chick cartilage microsomal enzyme preparation and UDP [14C] glucuronic acid and/or UDP-N-[3H] acetylgalactosamine. As previously reported by other investigators, a single sugar was added from UDP-[14C] glucuronic acid to the nonreducing end of pentasaccharide 6-sulfate and from UDP-N-[3H] acetylgalactosamine to the nonreducing end of hexasaccharide 6-sulfate. The labeled oligosaccharides were characterized by gel chromatography and degradation by chondroitinase ABC followed by identification of products. The oligosaccharides in concentrations above their Km inhibited chondroitin synthesis on endogenous primers, reinforcing the assumption that the enzymes involved in the additions to exogenous oligosaccharides are the same as those involved in chondroitin polymerization. When either the pentasaccharide 6-sulfate or hexasaccharide 6-sulfate was incubated in reaction mixtures containing both of the sugar nucleotides there was generally growth of oligosaccharide by two or three sugars. With longer incubation under conditions of limiting oligosaccharide concentration, as many as 14 to 16 sugars could be added but no further chondroitin polymerization took place. Addition of each sugar was shown to depend upon the concentration of appropriate acceptor but was otherwise independent of the addition of the alternate sugar. No paired addition of sugars was noted. It was concluded that two specific enzymes are involved in alternate additions of sugars to the oligosaccharides and that the two enzymes have no apparent interaction with one another. It is suggested that the rapid polymerization to form large chondroitin chains which previously has been shown to take place on endogenous primers is facilitated by interaction of the two enzymes with a component of the endogenous primer. This component is not present in the exogenous oligosaccharides since they do not serve in the same fashion as primers for polymerization.

Acetylgalactosamine↗
PubMed1978

Synthesis of the urinary glucuronic acid conjugate of N-hydroxy-4-aminobiphenyl.

The glucuronic acid conjugate of N-hydroxy-4-aminobiphenyl believed to be the carrier form responsible for transporting the active N-hydroxy compound from its site of formation in the liver to its site of carcinogenic action in the bladder has been prepared synthetically. The synthetic conjugate is identical by infrared and chromatographic analyses with the conjugate isolated from urine, thus unequivocally establishing its structure as an N--C conjugate, sodium (N,4-biphenyl-N-hydroxy-D-glucuronosylamine).

Aminobiphenyl Compounds↗
PubMed1981

Development of sarcomas in heterotopically transplanted rat urinary bladder unit exposed to glucuronic acid conjugate of N-hydroxy-4-aminobiphenyl.

The glucuronic acid conjugate of N-hydroxy-4-aminobiphenyl was tested for carcinogenicity using a heterotopically transplanted rat urinary bladder (HTB) diverted from urine flow. A low-grade transitional cell carcinoma developed in 1 of 16 HTB and sarcoma surrounding the Ommaya reservoir connected to HTB in 8 of 16 rats. This unexpected high incidence of sarcomas, not previously observed in HTB-carcinogenesis model, suggested that the glucuronide conjugate of N-hydroxy-4-aminobiphenyl is a locally active carcinogen to mesenchymal cells.

Aminobiphenyl Compounds↗
PubMed1992

Inhibition of human T cell leukemia virus by the plant flavonoid baicalin (7-glucuronic acid, 5,6-dihydroxyflavone).

The ability of baicalin (7-glucuronic acid, 5,6-dihydroxyflavone), a flavonoid compound purified from the Chinese medicinal herb, Scutellaria baicalensis georgi, to inhibit human T cell leukemia virus type I (HTLV-I) was examined. Baicalin produced concentration-dependent inhibition of HTLV-I replication in productively infected T and B cells. Moreover, baicalin treatment selectively reduced the detectable levels of HTLV-I p19 gag protein in infected cells by greater than 70% at concentrations that produced insignificant effects on total cellular protein and DNA synthesis with no loss in cell viability. Resistance to HTLV-I infection and virus-mediated transformation was noted in uninfected peripheral blood lymphocytes pretreated with baicalin before cocultivation with lethally irradiated chronically infected cells. Baicalin inhibited reverse transcriptase activity in HTLV-I-infected cells as well as the activity of purified reverse transcriptase from Moloney murine leukemia virus and Rous-associated virus type 2. These results suggest that baicalin may be a potential therapeutic agent against HTLV-I-associated T cell diseases.

Anti-Infective Agents↗
PubMed1988

Biotransformation of 1-dehydrotestosterone in the equine male castrate: identification of the neutral unconjugated and glucuronic acid conjugated metabolites in horse urine.

The in vivo biotransformation of (1,2(n)-3H)1-dehydrotestosterone was studied in three equine male castrates and a number of neutral metabolites were identified in the urinary unconjugated and glucuronic acid conjugate fractions by gas chromatography/mass spectrometry. The metabolites were extracted from aliquots of the 0-24 h urine samples by Amberlite XAD-2 and separated into combined unconjugated plus glucuronic acid conjugated and sulphoconjugated fractions by Sephadex LH-20 column chromatography. After enzymatic hydrolysis of the glucuronides, the crude neutral unconjugated steroids plus the aglycones were partially purified by Kieselgel H chromatography and identified as their methyloxime trimethylsilyl derivatives. In the unconjugated fraction, the major metabolites were isomers of androsta-1,4-diene-6,16,17-triol-3-one. In the aglycone fraction a small amount of the parent steroid was present but the major metabolite was the 17 alpha isomer androsta-1,4-dien-17 alpha-ol-3-one. Other metabolites containing the 1,4-dien-3-one group were isomers of androsta-1,4-diene-16,17-diol-3-one and androsta-1,4-diene-6,16-diol-3-one. Reduction of the 4-ene functionality leading to the formation of 5-androst-1-en-16-ol-3,17-dione, 5-androst-1-ene-16,17-diol-3-one and of the 1-ene functionality leading to the formation of testosterone and its further reduction leading to the formation of C19O2 and C19O3 androstane metabolites was observed. Some interesting features on the electron impact fragmentations of the methyloxime trimethylsilyl derivatives of steroids containing a 1,4-dien-3-one group were also observed.

Animals↗
PubMed1990

Defective glucuronic acid transport from lysosomes of infantile free sialic acid storage disease fibroblasts.

Separation by h.p.l.c. and pulsed amperometric detection were employed to measure glucuronic acid (GlcUA) and other acidic monosaccharides in fibroblasts from patients with infantile free sialic acid storage disease (ISSD) and Salla disease. These lysosomal storage disorders result from defective carrier-mediated transport of free N-acetylneuraminic acid (NeuAc) out of cellular lysosomes. Three Salla disease fibroblast strains stored approx. 0.4 nmol of free GlcUA/mg of cell protein, whereas four ISSD strains stored approx. 5 nmol GlcUA/mg (normal is undetectable). The GlcUA content of the mutant cell strains, which by differential centrifugation and Percoll gradient fractionation was localized to the lysosomes, averaged 5% of the free NeuAc content of the cells. N-Glycolylneuraminic acid (NeuGc) also accumulated in ISSD cells, but only when they were grown in the presence of fetal calf serum, which contains abundant NeuGc. No other acidic monosaccharides were detected in any of the mutant cell strains. GlcUA egress studies revealed that 56% of the initial GlcUA content was lost from normal granular fractions after 2 min at 37 degrees C. For similarly loaded ISSD granular fractions, virtually no GlcUA was lost even after 6 min. The results indicate that GlcUA is recognized and transported by the lysosomal NeuAc carrier, and that GlcUA transport is impaired in the lysosomal disorders of free NeuAc storage.

Biological Transport↗
PubMed1991

Circadian variation of hepatic UDP-glucuronic acid and the glucuronidation of xenobiotics in mice.

A circadian cycle in hepatic UDP-glucuronic acid (UDP-GA) concentration was observed in mice that was essentially the reverse of those seen for hepatic glycogen and UDP-glucose. That is, hepatic UDP-GA levels were highest during the fasting period and lowest during the feeding period. However, there was no significant difference between the half-lives or the apparent rates of glucuronidation for either acetaminophen or salicylamide at 8 a.m. and 5 p.m. Therefore, the previously-reported circadian variation in acetaminophen toxicity is probably due to circadian variation in hepatic glutathione levels rather than in hepatic glucuronidation capacity.

Acetaminophen↗
PubMed2004

Characterization of soluble and putative membrane-bound UDP-glucuronic acid decarboxylase (OsUXS) isoforms in rice.

Arabinoxylans in crop plants are the major sugar components of the cell walls, and UDP-xylose is a key substrate in the biosynthesis of xylans. In this study, the six putative UDP-D-glucuronic acid decarboxylase genes from rice (Oryza sativa UDP-xylose synthase; OsUXS) were cloned. Except for the soluble form of OsUXS3 (GenBank Accession No. \AB079064), the remaining five OsUXS enzymes contain a putative membrane-bound region. The six OsUXS genes were classified into three types by phylogenetic analysis and were expressed during the development of rice seeds. The HPLC retention times of the enzyme products and NMR data, indicate that the recombinant OsUXS2 enzyme catalyzes the conversion of UDP-D-glucuronic acid to UDP-D-xylose. Interestingly, the reactions catalyzed by the recombinant OsUXS2 and OsUXS3 enzymes were inhibited by NADP+, and accelerated by NADPH. The catalytic activities of the recombinant OsUXS2 and OsUXS3 enzymes were strongly inhibited by UDP, UTP, TDP, and TTP. The expression levels of OsUXS genes changed in different manners during the development of rice seeds, suggesting that each corresponding OsUXS enzyme plays a significant role in rice seed development at a certain stage. In the present study, we report that the UXS2-type enzyme of rice is not only characterized for the first time but also show significant findings involved in the gene expression of OsUXSs.

Amino Acid Motifs↗
PubMed1990

Effect of UDP-glucuronic acid depletion by salicylamide on biliary bilirubin excretion in the rat.

To determine the effect of UDP-glucuronic acid (UDPGA) depletion on bilirubin metabolism, salicylamide (SAM, which is metabolized primarily through glucuronidation, was administered to rats at a dose of 2 mmol/kg, and biliary bilirubin excretion and the proportion of bilirubin glucuronides were determined. At 15 min after administration of SAM, the UDPGA level in the liver was markedly decreased. Although the total biliary excretion of bilirubin showed no change, the bilirubin diglucuronide level in the 0- to 30-min period after SAM administration was significantly lower (36.9 +/- 4.3%) than that of the untreated control group during the same period (47.5 +/- 1.7%; P less than .01). The biliary bilirubin monoglucuronide (BMG) level in the 0- to 30-min period was significantly increased, compared with the control group. The C8-BMG/C12-BMG ratio in the 0- to 30-min period was significantly higher than that of the control group. At 150 min after SAM administration, there was an increase in the UDPGA level in the liver accompanied by an increase in bilirubin diglucuronide and a decrease in BMG. These results indicate that changes in UDPGA in the liver due to SAM administration influence the bilirubin composition of the bile.

Animals↗
PubMed1978

[Glucuronic acid, glucuronyltransferase and estrogens in breast cancer and precancer].

The glucuronic acid level in the serum and urine, the diural excretion of estrogens and 17-KS with the urine, the activity of glucuronyltransferase are reported in 101 patients with benign and malignant tumors and in 22 healthy females. The decrease in the activity of glucurolytransferase and increase in the percentage of free (nonconjugated) estrogens in patients with malignant tumors of the mammary gland are noted, the analogous results were obtained in patients with benign tumors, but these are statistically insignificant. The decrease of the glucuronyltransferase activity is suggested to result in the development of relative hyperestrogen in normal total excretion.

17-Ketosteroids↗
PubMed1982

The kinetic mechanism of the major form of ox kidney aldehyde reductase with D-glucuronic acid.

The steady-state kinetics of the major form of ox kidney aldehyde reductase with d-glucuronic acid have been determined at pH7. Initial rate and product inhibition studies performed in both directions are consistent with a Di-Iso Ordered Bi Bi mechanism. The mechanism of inhibition by sodium valproate and benzoic acid is shown to involve flux through an alternative pathway.

Alcohol Oxidoreductases↗
PubMed1965

RETINOYL BETA-GLUCURONIC ACID: A MAJOR METABOLITE OF VITAMIN A IN RAT BILE.

The major metabolite in rat bile of injected C(14)-retinoic acid was purified by ion-exchange and silicic acid chromatography; it has the spectrum of methyl retinoate, releases retinoic acid upon basic hydrolysis or by treatment with beta-glucuronidase, and contains glucuronic acid. The metabolite was characterized by treatment with diazomethane followed by hexamethyl-disilazane, or with periodate followed by semicarbazide, and the products were chromatographed. The metabolite has been tentatively identified as retinoyl beta-glucuronide.

Bile↗
PubMed2005

Synthesis and structural analysis of the anilides of glucuronic acid and orientation of the groups on the carbohydrate scaffolding.

[structures: see text] The synthesis of anilides derived from glucuronic acid is described. Secondary anilides had a Z configuration in the solid state and showed intramolecular and intermolecular hydrogen bonding. However, on the basis of NMR and IR studies, there was generally no evidence for the same hydrogen bonding in solution. Tertiary anilides showed a strong preference for the E configuration on the basis of NOE studies and molecular mechanics calculations. The alkylation of the secondary anilides induces a configurational switch that alters the orientation of the aromatic group with respect to the pyranose, which has relevance for presentation or orientation of pharmacophoric groups on carbohydrate scaffolds.

Anilides↗