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UDP-galactose (Gal), UDP-glucose ..

AB - The enzyme activities of ceramide galactosyltransferase and ceramide glucosyltransferase were assayed as a function of time (0, 1, 2, 4, 7, 14, 21, 28, and 35 days) after crush injury or permanent transection of the adult rat sciatic nerve. These experimental models of neuropathy are characterized by the presence and absence of axonal regeneration and subsequent myelin assembly. Within the first 4 days after both injuries, a 50% reduction of ceramide galactosyltransferase-specific activity was observed compared to values found in the normal adult nerve. This activity remained unchanged at 7 days after injury; however, by 14 days the ceramide galactosyltransferase activity diverged in the two models. The activity increased in the crushed nerve and reached control values by 21 days, whereas a further decrease was observed in the transected nerve such that the activity was nearly immeasurable by 35 days. In contrast, the ceramide glucosyltransferase activity showed a rapid increase between 1 and 4 days, followed by a plateau that was 3.4-fold greater than that in the normal adult nerve, which persisted throughout the observation period in both the crush and transection models. [3H]Galactose precursor incorporation studies at 7, 14, 21, and 35 days after injury confirmed the previously observed shift in biosynthesis from the galactocerebrosides during myelin assembly in the crush model to the glucocerebrosides and oligohexosylceramide homologues in the absence of myelin assembly in the transection model. The transected nerves were characterized by a peak of biosynthesis of the glucocerebrosides at 14 days. Of particular interest is the biosynthesis of the glucocerebrosides and the oligohexosylceramides at 7 and 14 days after crush injury. This biosynthesis was dramatically reduced by 21 days after crush, even though the ceramide glucosyltransferase activity remained elevated. The present data indicate that this shift in myelination-dependent glycolipid biosynthesis is controlled at least partially at the level of these sugar transferases.

Lactase also catalyzes the conversion of phlorizin to phloretin and glucose

► Xylose and galactose are components of Trichomonas vaginalis glycans. ► T. vaginalis UDP-xylose synthase and UDP-galactose epimerase genes identified. ► Enzymes were expressed in recombinant form, purified and assayed.

The Biosynthesis of UDP-Galacturonic Acid in ..

The presence of xylose and galactose residues in the structure of trichomonad lipoglycans was indicated by previous studies and the modification of any glycoconjugate with either monosaccharide requires the respective presence of the nucleotide sugars, UDP-xylose and UDP-galactose. Biosynthesis of UDP-xylose de novo is mediated by UDP-xylose synthase (UXS; UDP-glucuronic acid decarboxylase), which converts UDP-glucuronic acid to UDP-xylose, whereas UDP-galactose can be generated from UDP-glucose by UDP-galactose epimerases (GalE). Trichomonas vaginalis cDNAs, encoding proteins with homology to these enzymes from other eukaryotes, were isolated. The recombinant T. vaginalis UDP-xylose synthase and UDP-galactose epimerase were expressed in Escherichia coli and tested via high pressure liquid chromatography to demonstrate their enzymatic activities. Thereby, in this first report on enzymes involved in glycoconjugate biosynthesis in this organism, we demonstrate the existence of xylose and galactose synthesising pathways in T. vaginalis.

N2 - The enzyme activities of ceramide galactosyltransferase and ceramide glucosyltransferase were assayed as a function of time (0, 1, 2, 4, 7, 14, 21, 28, and 35 days) after crush injury or permanent transection of the adult rat sciatic nerve. These experimental models of neuropathy are characterized by the presence and absence of axonal regeneration and subsequent myelin assembly. Within the first 4 days after both injuries, a 50% reduction of ceramide galactosyltransferase-specific activity was observed compared to values found in the normal adult nerve. This activity remained unchanged at 7 days after injury; however, by 14 days the ceramide galactosyltransferase activity diverged in the two models. The activity increased in the crushed nerve and reached control values by 21 days, whereas a further decrease was observed in the transected nerve such that the activity was nearly immeasurable by 35 days. In contrast, the ceramide glucosyltransferase activity showed a rapid increase between 1 and 4 days, followed by a plateau that was 3.4-fold greater than that in the normal adult nerve, which persisted throughout the observation period in both the crush and transection models. [3H]Galactose precursor incorporation studies at 7, 14, 21, and 35 days after injury confirmed the previously observed shift in biosynthesis from the galactocerebrosides during myelin assembly in the crush model to the glucocerebrosides and oligohexosylceramide homologues in the absence of myelin assembly in the transection model. The transected nerves were characterized by a peak of biosynthesis of the glucocerebrosides at 14 days. Of particular interest is the biosynthesis of the glucocerebrosides and the oligohexosylceramides at 7 and 14 days after crush injury. This biosynthesis was dramatically reduced by 21 days after crush, even though the ceramide glucosyltransferase activity remained elevated. The present data indicate that this shift in myelination-dependent glycolipid biosynthesis is controlled at least partially at the level of these sugar transferases.

GALE UDP-Galactose-4-Epimerase Human Recombinant …

Trichomonas vaginalis is a parasitic flagellated protozoan which causes human trichomoniasis, one of the most common sexually transmitted diseases in humans. Despite its wide spread and high prevalence, with more than 200 million affected people and at least three million new cases per year in the USA , it has proven to be an underestimated disease. Indeed, an infection with T. vaginalis causes not only vaginitis, exocervicitis and urethritis, it is also implicated in miscarriages and occurrence of human immunodeficiency virus. Cytopathogenicity starts with the adhesion of the protozoan to the host cell and indeed glycoconjugates such as a lipoglycan covering its cell surface are important for the parasite's interaction with its host . The structure of this lipoglycan , as well as of its protein-linked N-glycans , have been recently determined to contain monosaccharides such as xylose and galactose. In order to perform the relevant xylosylation and galactosylation reactions necessary for the biosynthesis of these glycan structures in vivo, the organism requires the relevant nucleotide sugars, UDP-xylose and UDP-galactose.

UDP-xylose is the product of a two-step conversion from UDP-glucose: first, dehydrogenation of UDP-glucose is catalyzed by UDP-glucose dehydrogenase (UGD, EC 1.1.1.22) thus forming UDP-glucuronic acid (UDP-GlcA). Then, UDP-glucuronic acid decarboxylase (UDP-xylose synthase; UXS, EC 4.1.1.35) acts on UDP-GlcA to form UDP-xylose . Depending on the organism, UXS may be cytosolically or lumenally located. In plants, the biosynthesis of UDP-xylose by different UXS isoforms occurs both in the cytosol and in membrane-bound compartments . Mammals and nematodes on the other hand express only one UXS, which is located in the golgi apparatus , whereas the fungus Cryptococcus expresses only one, probably cytosolic, form . In bacteria such as Micromonospora echinospora and Sinorhizoboium meliloti UDP-xylose is also synthesised from UDP-glucuronic acid . On the other hand, the de novo biosynthesis of UDP-galactose from UDP-glucose is mediated by the cytosolic UDP-galactose epimerase (GalE; EC 5.1.3.2); the relevant GalE genes have been identified from a number of organisms and in T. brucei GalE is essential for growth .

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UDP galactose epimerase - Revolvy

The enzyme activities of ceramide galactosyltransferase and ceramide glucosyltransferase were assayed as a function of time (0, 1, 2, 4, 7, 14, 21, 28, and 35 days) after crush injury or permanent transection of the adult rat sciatic nerve. These experimental models of neuropathy are characterized by the presence and absence of axonal regeneration and subsequent myelin assembly. Within the first 4 days after both injuries, a 50% reduction of ceramide galactosyltransferase-specific activity was observed compared to values found in the normal adult nerve. This activity remained unchanged at 7 days after injury; however, by 14 days the ceramide galactosyltransferase activity diverged in the two models. The activity increased in the crushed nerve and reached control values by 21 days, whereas a further decrease was observed in the transected nerve such that the activity was nearly immeasurable by 35 days. In contrast, the ceramide glucosyltransferase activity showed a rapid increase between 1 and 4 days, followed by a plateau that was 3.4-fold greater than that in the normal adult nerve, which persisted throughout the observation period in both the crush and transection models. [3H]Galactose precursor incorporation studies at 7, 14, 21, and 35 days after injury confirmed the previously observed shift in biosynthesis from the galactocerebrosides during myelin assembly in the crush model to the glucocerebrosides and oligohexosylceramide homologues in the absence of myelin assembly in the transection model. The transected nerves were characterized by a peak of biosynthesis of the glucocerebrosides at 14 days. Of particular interest is the biosynthesis of the glucocerebrosides and the oligohexosylceramides at 7 and 14 days after crush injury. This biosynthesis was dramatically reduced by 21 days after crush, even though the ceramide glucosyltransferase activity remained elevated. The present data indicate that this shift in myelination-dependent glycolipid biosynthesis is controlled at least partially at the level of these sugar transferases.

of Leishmania major in UDP-galactose biosynthesis

In the case of UDP-galactose epimerase, the two identified (TVAG_186740 and TVAG_101620) open reading frames predicted protein sequences of 340 residues with 92% identity. Therefore we decided to clone only one of these cDNAs and designated the reading frame TVAG_186740 as GalE1. One consistent nucleotide alteration in three cDNA clones suggests that the GalE1 from the C1 strain differs in one non-conserved amino acid as compared to the G3 strain (residue 98 is Glu rather than Lys). The trichomonad GalE1 is 57% identical to the 335 amino acids long human homologue and 38% to the characterised T. cruzi enzyme (). Incubations to test epimerase activity were analysed using the same ion-pair RP-HPLC system as for the UDP-xylose synthase assays; it was found that T. vaginalis GalE1 could convert UDP-glucose into UDP-galactose and vice versa with final ratios of either 22:78 or 24:76 UDP-Gal:UDP-Glc (D), suggesting that the equilibrium favours the formation of UDP-Glc. A similar ratio of 1:3 UDP-Gal:UDP-Glc was found when using Saccharomyces fragilis as a source of epimerase activity . A control experiment with the purified T. vaginalis UXS indicated no such conversion, verifying that no UDP-galactose epimerase activity from the E. coli host was present in fractions eluted from the Ni(II)-chelation column.

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