Alpha1,3-fucosyltransferase 9 (FUT9; Fuc-TIX) preferentially fucosylates the distal GlcNAc residue of polylactosamine chain while the other four alpha1,3FUT members preferentially fucosylate the inner GlcNAc residue. (49/1610)

We analyzed the substrate specificity of six human alpha1,3-fucosyltransferases (alpha1,3FUTs) for the 2-aminobenzamide (2AB)-labelled polylactosamine acceptor, Galbeta1-4GlcNAcbeta1-3Galbeta1-4GlcNAcbeta1- 3Galbeta1-4GlcNAc-2AB (3LN-2AB). FUT9 preferentially fucosylated the distal GlcNAc residue of the polylactosamine chain while the other four alpha1,3FUT members, FUT3, FUT4, FUT5 and FUT6, preferentially fucosylated the inner GlcNAc residue. This indicated that FUT9 exhibits more efficient activity for the synthesis of Lewis x carbohydrate epitope (Le(x); CD15; stage-specific embryonal antigen-1 (SSEA-1)). In contrast, the other four members synthesize more effectively the internal Le(x) epitope. FUT7 could not transfer a fucose to an acceptor which is non-sialylated.  (+info)

Family 19 chitinases of Streptomyces species: characterization and distribution. (50/1610)

Chitinase C from Streptomyces griseus HUT6037, described in 1997, is the first family 19 chitinase found in an organism other than higher plants. In this study, some properties of chitinase C were compared with those of family 18 bacterial chitinases, and the distribution of family 19 chitinases in Streptomyces species was investigated. The specific hydrolysing activity of chitinase C against soluble and insoluble chitinous substrates was markedly higher than those of bacterial family 18 chitinases. Chitinase C exhibited marked antifungal activity, whereas the other bacterial chitinases examined had no antifungal activity. Chitinase C was insensitive to allosamidin, whereas the family 18 bacterial chitinases were sensitive. Taking advantage of this insensitivity to allosamidin, a search was made for family 19 chitinases in various Streptomyces species. Chitinases insensitive to allosamidin were detected in the culture supernatants of all tested Streptomyces species. Southern hybridization analysis using a labelled DNA fragment corresponding to the catalytic domain of chitinase C strongly suggested that these species have genes similar to the chiC gene of S. griseus HUT6037. DNA fragments corresponding to the major part of the catalytic domains were amplified by PCR. The amplified fragments encoded amino acid sequences very similar to that of the corresponding region of chitinase C. Therefore, it was concluded that Streptomyces species generally possess family 19 chitinases which are very similar to chitinase C. Comparison of their amino acid sequences with those of plant family 19 chitinases revealed that Streptomyces family 19 chitinases are class IV type in terms of the presence and positions of deletions of amino acid sequences which are characteristic of plant class IV chitinases.  (+info)

The N-terminal region of the Escherichia coli WecA (Rfe) protein, containing three predicted transmembrane helices, is required for function but not for membrane insertion. (51/1610)

The correct site for translation initiation for Escherichia coli WecA (Rfe), presumably involved in catalyzing the transfer of N-acetylglucosamine 1-phosphate to undecaprenylphosphate, was determined by using its FLAG-tagged derivatives. The N-terminal region containing three predicted transmembrane helices was found to be necessary for function but not for membrane localization of this protein.  (+info)

Clustering of cell surface (beta)1,4-galactosyltransferase I induces transient tyrosine phosphorylation of focal adhesion kinase and loss of stress fibers. (52/1610)

It is well appreciated that clustering of receptors for the extracellular matrix, most notably the integrins, elicits intracellular signal cascades. One of the first indications that integrin-dependent signaling has occurred is by the activation of focal adhesion kinase (FAK). Another, although less well understood, receptor for the extracellular matrix is (beta)1, 4-galactosyltransferase I (GalT). GalT participates during lamellipodia formation and cell migration by recognizing terminal N-acetylglucosamine residues on basal lamina glycosides. In this study, we investigated whether GalT is also capable of eliciting intracellular signal cascades, specifically FAK activation, in response to ligand binding and/or aggregation. 3T3 fibroblasts were treated with two different reagents capable of aggregating GalT, either antibodies raised against recombinant GalT or multivalent polymers of N-acetylglucosamine, and the effects on tyrosine phosphorylation were analyzed. Both reagents induced an initial tyrosine phosphorylation (1-2 minutes) and subsequent dephosphorylation (5-10 minutes) of proteins with molecular mass 67 and 125 kDa. These proteins were identified as paxillin and FAK, respectively, by immunoprecipitation with anti-paxillin and anti-FAK antibodies. Preimmune IgG, anti-GalT Fab fragments, irrelevant polymers and monomeric N-acetylglucosamine had no effect. The ability of GalT aggregation to induce transient tyrosine phosphorylation was dependent upon cell density. In addition, FAK dephosphorylation was found to be sensitive to the phosphatase inhibitor, sodium pervanadate. Similar to the integrins, GalT requires association with the cytoskeleton in order to function as a matrix receptor. To determine if the transient tyrosine phosphorylation of FAK was dependent upon GalT binding to the cytoskeleton, stably transfected fibroblasts expressing different amounts of GalT were treated with polymeric N-acetylglucosamine. Cells expressing increased levels of GalT associated with the cytoskeleton showed increased levels of FAK tyrosine phosphorylation and prolonged dephosphorylation, relative to control cells. In contrast, cells in which a dominant negative form of GalT prevents association with the cytoskeleton showed no or weak response to polymeric N-acetylglucosamine. Concomitant with the GalT-stimulated dephosphorylation of FAK, cells treated with anti-GalT antibodies or polymeric N-acetylglucosamine showed a loss of actin stress fibers and focal adhesions. Pervanadate treatment inhibited the GalT-dependent loss of actin stress fibers. To confirm the requirement of GalT in transient FAK phosphorylation and stress fiber reorganization in this system, we created cells homozygous null for the GalT isoform that functions as a matrix receptor. These cells were incapable of phosphorylating FAK in response to GalT agonists and, interestingly, showed a lack of lamellar stress fibers when cultured on basal lamina matrices. These data suggest that GalT function as a basal lamina receptor involves transient activation of FAK and an associated reorganization of stress fibers.  (+info)

Enzyme replacement therapy in a mouse model of aspartylglycosaminuria. (53/1610)

Aspartylglycosaminuria (AGU), the most common lysosomal disorder of glycoprotein degradation, is caused by deficient activity of glycosylasparaginase (AGA). AGA-deficient mice share most of the clinical, biochemical and histopathologic characteristics of human AGU disease. In the current study, recombinant human AGA administered i.v. to adult AGU mice disappeared from the systemic circulation of the animals in two phases predominantly into non-neuronal tissues, which were rapidly cleared from storage compound aspartylglucosamine. Even a single AGA injection reduced the amount of aspartylglucosamine in the liver and spleen of AGU mice by 90% and 80%, respectively. Quantitative biochemical analyses along with histological and immunohistochemical studies demonstrated that the pathophysiologic characteristics of AGU were effectively corrected in non-neuronal tissues of AGU mice during 2 wk of AGA therapy. At the same time, AGA activity increased to 10% of that in normal brain tissue and the accumulation of aspartylglucosamine was reduced by 20% in total brain of the treated animals. Immunohistochemical studies suggested that the corrective enzyme was widely distributed within the brain tissue. These findings suggest that AGU may be correctable by enzyme therapy.-Dunder, U., Kaartinen, V., Valtonen, P., Vaananen, E., Kosma, V.-M., Heisterkamp, N., Groffen, J., Mononen, I. Enzyme replacement therapy in a mouse model of aspartylglycosaminuria.  (+info)

Two carbohydrate recognition domains of Hyphantria cunea lectin bind to bacterial lipopolysaccharides through O-specific chain. (54/1610)

We previously identified a novel lectin cDNA from the fall webworm [Shin et al. (1998) Insect Biochem. Mol. Biol. 28, 827-837], which encodes two carbohydrate recognition domains (CRD-N and CRD-C) and is up-regulated following bacterial challenge. The lipopolysaccharide (LPS) binding activities of the recombinant CRD-N and CRD-C (rCRD-N and rCRD-C) were investigated by enzyme-linked immunosorbent assay. The LPS binding of rCRD-N and rCRD-C was pH-dependent: at pH below 6.0, they show a higher binding ability to LPS. The binding of the rCRD-N was inhibited by both D-mannose and N-acetyl-D-glucosamine, whereas the binding of the rCRD-C was inhibited only by D-mannose. The binding of both rCRD-N and rCRD-C to Escherichia coli was mainly mediated through the O-specific chain.  (+info)

Regiospecific glycosidase-assisted synthesis of lacto-N-biose I (Galbeta1-3GlcNAc) and 3'-sialyl-lacto-N-biose I (NeuAcalpha2-3Galbeta1-3GlcNAc). (55/1610)

The all-transglycolytic synthesis of lacto-N-biose I (Galbeta1-3GlcNAc) and 3'-sialyl-lacto-N-biose I (NeuAcalpha2-3Galbeta1-3GlcNAc) was performed. The disaccharide lacto-N-biose I was obtained by use of p-nitrophenyl beta-D-galactopyranoside as the donor, 2-acetamido-2-deoxy-D-glucopyranose as the acceptor and Xanthomonas manihotis beta-D-galactosidase as the catalyst. The reaction was shown to be regiospecific, with a high molar yield (about 55%) with respect to the donor. Lacto-N-biose I obtained by this method was used as the acceptor for a subsequent enzymatic reaction catalyzed by Trypanosoma cruzi trans-sialidase in which 2'-(4-methylumbellyferyl)-alpha-D-N-acetylneuraminic was used as the donor of the N-acetylneuraminil moiety. The reaction generated the product, 3'-sialyl-lacto-N-biose I, regiospecifically and with a molar yield of about 35%.  (+info)

Abnormalities in the glycosphingolipid content of human Pk and p erythrocytes. (56/1610)

Erythrocytes of the rare Pk phenotype lack the blood group P antigen, and p erythrocytes lack both P and Pk antigens. On the basis of immunological data we suggested previously that the P and Pk antigens are the glycosphingolipids globoside and trihexosyl ceramide, respectively, and we have now confirmed these designations by chemical analysis of erythrocytes lacking these antigens. The Pk erythrocytes contain only traces of globoside and have a marked excess of trihexosyl ceramide in comparison with normal erythrocytes. The p erythrocytes lack globoside and trihexosyl ceramide and contain an excess of lactosyl ceramide and other complex glycolipids. Our analyses of normal erythrocytes also revealed complex gangliosides with the approximate chromatographic mobilities of GD1b and GT1, and several gangliosides containing N-acetylglucosamine.  (+info)