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Kevin R. Nicholas - One of the best experts on this subject based on the ideXlab platform.
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the expression of β 1 3 galactosyltransferase and β 1 4 galactosyltransferase enzymatic activities in the mammary gland of the tammar wallaby macropus eugenii during early lactation
Biochimica et Biophysica Acta, 2007Co-Authors: K K Menzies, Kevin R. NicholasAbstract:Abstract The regulation of β-1,3 galactosyltransferase (3βGalT) and β-1,4 galactosyltransferase enzymatic (4βGalT) activities in the mammary gland of the tammar wallaby (Macropus eugenii) have been characterised. These two β-Galactosyltransferases are active at different times during the lactation cycle and play a central role in regulating the carbohydrate composition in tammar milk, which changes progressively throughout lactation to assist the physiological development of the altrical young. The 4βGalT activity was present at parturition and increased 3-fold by day 10 of lactation (d10L), whereas 3βGalT activity was barely detectable at day d5L and then increased 6-fold by d10L. This increase in activity of both enzymes was sucking dependent. While 3βGalT activity was not observed in the mammary gland prior to d7L, this activity was found in mammary explants from late pregnant tammar cultured with insulin, hydrocortisone and prolactin (IFP) and was further stimulated by the addition of tri-iodothyronine (T) and 17β-oestradiol (E). The activity of 4βGalT in these explants was stimulated maximally with IFP. These data suggest the temporal activity of both 3βGalT and 4βGalT is most likely regulated by both endocrine stimuli and factors intrinsic to the mammary gland.
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Biosynthesis of marsupial milk oligosaccharides: characterization and developmental changes of two Galactosyltransferases in lactating mammary glands of the tammar wallaby, Macropus eugenii.
Biochimica et Biophysica Acta, 1991Co-Authors: Michael Messer, Kevin R. NicholasAbstract:Abstract Tammar wallaby ( Macropus eugenii ) mammary glands contain two Galactosyltransferases of which the first, 4βGalT, is a UDP-galactose: N -acetylglucosaminyl β 1 → 4-galactosyltransferase equivalent to the A protein of the lactose synthase of eutherian mammals. The second enzyme, 3βGalT, is a UDP-galactose:lactose β 1 → 3-galactosyltransferase, not previously identified in mammary glands of any species, which catalyses the formation pf Gal β 1 → 3Gal β 1 → 4Glc from lactose. The two enzyme activities, as well as the lactose synthase activity, have been characterised with respect to the effects of pH, apparent K m values, effects of bovine and tammar α-lactalbumins, heat sensitivity and identity of products. Studies on the substrate specificity and heat sensitivity of the 3βGalT activity suggest that this enzyme may catalyse the β-galactosylation of Gal β 1 3Gal β 1 → 4Glc as well as of lactose. The activity of the 3βGalT, unlike that of the 4βGalT, changes dramatically during the course of lactation in parallel with similar changes in the carbohydrate content of tammar milk.
Thierry Hennet - One of the best experts on this subject based on the ideXlab platform.
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Identification of Domains and Amino Acids Essential to the Collagen Galactosyltransferase Activity of GLT25D1
2011Co-Authors: Claire Perrin-tricaud, Christoph Rutschmann, Thierry HennetAbstract:Collagen is modified by hydroxylation and glycosylation of hydroxylysine residues. This glycosylation is initiated by the b1,O Galactosyltransferases GLT25D1 and GLT25D2. The structurally similar protein cerebral endothelial cell adhesion molecule CEECAM1 was previously reported to be inactive when assayed for collagen glycosyltransferase activity. To address the cause of the absent galactosyltransferase activity, we have generated several chimeric constructs between the active human GLT25D1 and inactive human CEECAM1 proteins. The assay of these chimeric constructs pointed to a short central region and a large C-terminal region of CEECAM1 leading to the loss of collagen galactosyltransferase activity. Examination of the three DXD motifs of the active GLT25D1 by site-directed mutagenesis confirmed the importance of the first (amino acids 166–168) and second motif (amino acids 461–463) for enzymatic activity, whereas the third one was dispensable. Since the second DXD motif is incomplete in CEECAM1, we have restored the motif by introducing the substitution S461D. This change did not restore the activity of the C-terminal region, thereby showing that additional amino acids were required in this C-terminal region to confer enzymatic activity. Finally, we have introduced the substitution Q471R-V472M-N473Q-P474V in the CEECAM1-C-terminal construct, which is found in most animal GLT25D1 and GLT25D2 isoforms but not in CEECAM1. This substitution was shown to partially restore collagen galactosyltransferase activity, underlining its importance for catalytic activity in the C-terminal domain. Because multiple mutations in different regions of CEECAM1 contribute to th
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core glycosylation of collagen is initiated by two β 1 o Galactosyltransferases
Molecular and Cellular Biology, 2009Co-Authors: Belinda Schegg, Andreas J Hulsmeier, Christoph Rutschmann, Charlotte Maag, Thierry HennetAbstract:Collagen is a trimer of three left-handed alpha chains representing repeats of the motif Gly-X-Y, where (hydroxy)proline and (hydroxy)lysine residues are often found at positions X and Y. Selected hydroxylysines are further modified by the addition of galactose and glucose-galactose units. Collagen glycosylation takes place in the endoplasmic reticulum before triple-helix formation and is mediated by β(1-O)galactosyl- and α(1-2)glucosyltransferase enzymes. We have identified two collagen Galactosyltransferases using affinity chromatography and tandem mass spectrometry protein sequencing. The two collagen β(1-O)Galactosyltransferases corresponded to the GLT25D1 and GLT25D2 proteins. Recombinant GLT25D1 and GLT25D2 enzymes showed a strong galactosyltransferase activity toward various types of collagen and toward the serum mannose-binding lectin MBL, which contains a collagen domain. Amino acid analysis of the products of GLT25D1 and GLT25D2 reactions confirmed the transfer of galactose to hydroxylysine residues. The GLT25D1 gene is constitutively expressed in human tissues, whereas the GLT25D2 gene is expressed only at low levels in the nervous system. The GLT25D1 and GLT25D2 enzymes are similar to CEECAM1, to which we could not attribute any collagen galactosyltransferase activity. The GLT25D1 and GLT25D2 genes now allow addressing of the biological significance of collagen glycosylation and the importance of this posttranslational modification in the etiology of connective tissue disorders.
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The galactosyltransferase family.
Cellular and molecular life sciences : CMLS, 2002Co-Authors: Thierry HennetAbstract:Galactose is transferred via several linkages to acceptor structures by galactosyltransferase enzymes. In prokaryotes, galactose is mainly found on lipopolysaccharides and capsular polysaccharides. In eukaryotes, Galactosyltransferases, which are localized in the Golgi apparatus, are involved in the formation of several classes of glycoconjugates and in lactose biosynthesis. Although they sometimes catalyze identical reactions, prokaryotic and eukaryotic Galactosyltransferases share only little structural similarities. In mammals, 19 distinct galactosyltransferase enzymes have been characterized to date. These enzymes catalyze the transfer of galactose via β1-4, β1-3, α1-3 and α1-4 linkages. The present review focuses on the description of these mammalian Galactosyltransferases.
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β3-Galactosyltransferase-I, -II, and -III
Handbook of Glycosyltransferases and Related Genes, 2002Co-Authors: Thierry Hennet, Eric G BergerAbstract:In higher eukaryotes, galactose is commonly found in all classes of glycoconjugates, where it is bound as either α- or β-anomer through 1,3- or 1,4-linkage to various carbohydrate acceptor substrates. Families of Galactosyltransferases are defined according to the type of linkage catalyzed. Purification studies have suggested the existence of several enzymes in each galactosyltransferase family, assumptions which have been confirmed by the recent cloning of genes encoding Galactosyltransferases. However, the number of galactosyltransferase genes isolated has far surpassed these early predictions. The characterization of the members of each galactosyltransferase family has revealed differences in the patterns of tissue expression and in acceptor substrate specificity, although a certain degree of redundancy prevails between Galactosyltransferases from a given family. For example, four β3-galactosyltransferase (β3GalT) genes have been described that direct the expression of enzymes linking Galβ1,3 to GlcNAc (Hennet et al. 1998; Kolbinger et al. 1998; Amado et al. 1998; Isshiki et al. 1999; Zhou et al. 1999a). A comparison between β3GalT proteins unraveled several conserved domains not found in other Galactosyltransferases. Surprisingly, a β3-N-acetylglucosaminyltransferase enzyme as well as proteins homologous to the Drosophila signaling proteins Brainiac and Fringe were also identified among the β3GalT-related proteins. β3GalTs participate in the shaping of several oligosaccharide structures in O-glycans, N-glycans and glycolipids. This review summarizes the properties of three β3GalT enzymes that direct the formation of type-1 chains, the support of Lea and Leb antigens.
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Biosynthesis of the Linkage Region of Glycosaminoglycans CLONING AND ACTIVITY OF GALACTOSYLTRANSFERASE II, THE SIXTH MEMBER OF THE β1,3-GALACTOSYLTRANSFERASE FAMILY (β3GalT6)
The Journal of biological chemistry, 2001Co-Authors: Xiaomei Bai, Thierry Hennet, Dapeng Zhou, Jillian R. Brown, Brett E. Crawford, Jeffrey D EskoAbstract:A family of five beta1,3-Galactosyltransferases has been characterized that catalyze the formation of Galbeta1,3GlcNAcbeta and Galbeta1,3GalNAcbeta linkages present in glycoproteins and glycolipids (beta3GalT1, -2, -3, -4, and -5). We now report a new member of the family (beta3GalT6), involved in glycosaminoglycan biosynthesis. The human and mouse genes were located on chromosomes 1p36.3 and 4E2, respectively, and homologs are found in Drosophila melanogaster and Caenorhabditis elegans. Unlike other members of the family, beta3GalT6 showed a broad mRNA expression pattern by Northern blot analysis. Although a high degree of homology across several subdomains exists among other members of the beta3-galactosyltransferase family, recombinant enzyme did not utilize glucosamine- or galactosamine-containing acceptors. Instead, the enzyme transferred galactose from UDP-galactose to acceptors containing a terminal beta-linked galactose residue. This product, Galbeta1,3Galbeta is found in the linkage region of heparan sulfate and chondroitin sulfate (GlcAbeta1,3Galbeta1,3Galbeta1,4Xylbeta-O-Ser), indicating that beta3GalT6 is the so-called galactosyltransferase II involved in glycosaminoglycan biosynthesis. Its identity was confirmed in vivo by siRNA-mediated inhibition of glycosaminoglycan synthesis in HeLa S3 cells. Its localization in the medial Golgi indicates that this is the major site for assembly of the linkage region.
Irma Van Die - One of the best experts on this subject based on the ideXlab platform.
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molecular cloning of a human cdna encoding β 1 4 galactosyltransferase with 37 identity to mammalian udp gal glcnac β 1 4 galactosyltransferase
Proceedings of the National Academy of Sciences of the United States of America, 1998Co-Authors: Takeshi Sato, Kiyoshi Furukawa, Hans Bakker, Dirk H Van Den Eijnden, Irma Van DieAbstract:A cDNA encoding a β-1,4-galactosyltransferase named β-1,4-GalT II was cloned from a cDNA library of the human breast tumor cell line, MRK-nu-1. Initially, a 860-bp PCR fragment was obtained from MRK-nu-1 mRNA by 3′-rapid amplification of cDNA ends by using two nested degenerate oligonucleotide primers based on a highly conserved amino acid sequence found in the catalytic domain of mammalian β-1,4-Galactosyltransferases and Lymnaea stagnalis β-1,4-N-acetylglucosaminyltransferase (β-1,4-GlcNAcT), both of which utilize the same sugar acceptor. This subsequently was used as a probe to isolate a 4.7-kb cDNA that contained an ORF of 1,164 bp predicting a polypeptide of 388 aa. Its deduced amino acid sequence shows an identity of 37% with that of the previously characterized human β-1,4-galactosyltransferase (referred to as β-1,4-GalT I) and of 28% with that of L. stagnalis β-1,4-GlcNAcT. Study of the properties of the β-1,4-GalT II fused to protein A expressed as a soluble form in COS-7 cells revealed that it is a genuine β-1,4-GalT but has no lactose synthetase activity in the presence of α-lactalbumin. Northern blot analysis of 24 human tissues showed that they all express the β-1,4-GalT II transcript, although the levels varied. These results indicate that human cells contain another β-1,4-GalT.
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a lymnaea stagnalis gene with sequence similarity to that of mammalian beta 1 4 Galactosyltransferases encodes a novel udp glcnac glcnac beta r beta 1 4 n acetylglucosaminyltransferase
Journal of Biological Chemistry, 1994Co-Authors: Hans Bakker, Dirk H Van Den Eijnden, M Agterberg, A Van Tetering, Carolien A M Koeleman, Irma Van DieAbstract:A cDNA encoding a novel glycosyltransferase, that may be involved in a variant pathway for the synthesis of complex type oligosaccharide chains, was cloned from the pond snail Lymnaea stagnalis. By heterologous hybridization, using bovine beta 1-->4-galactosyltransferase cDNA as probe, a genomic clone from a snail library was isolated. This genomic clone was subsequently used to clone the corresponding cDNA from a prostate gland library. The isolated cDNA encodes a polypeptide of 490 amino acids with a type II membrane protein topology typical for glycosyltransferases. The carboxyl-terminal part, encoding the putative catalytic domain, reveals considerable sequence similarity with the corresponding region of mammalian beta 1-->4-Galactosyltransferases, suggesting an evolutionary relationship. Expression of this cDNA in COS cells and insect cells revealed that the encoded enzyme transfers GlcNAc, rather than Gal or GalNAc, from the corresponding nucleotide sugars to several beta-N-acetylglucosaminides. Structural characterization by 1H NMR spectroscopy of products formed in vitro demonstrated that the enzyme can be identified as a UDP-GlcNAc:GlcNAc beta-R beta 1-->4-N-acetylglucosaminyl-transferase. A new family of glycosyltransferases has hereby been discovered, consisting of enzymes that act on acceptor substrates with a terminal beta-linked GlcNAc residue and establish a beta 1-->4-linkage, but have a different nucleotide sugar requirement.
Christelle Breton - One of the best experts on this subject based on the ideXlab platform.
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Fold recognition study of α3-galactosyltransferase and molecular modeling of the nucleotide sugar-binding domain
Glycobiology, 1999Co-Authors: Anne Imberty, Cédric Monier, Emmanuel Bettler, Solange Moréra, Paul S. Freemont, Manfred J. Sippl, Hannes Flöckner, Wolfgang Rüger, Christelle BretonAbstract:The structure and fold of the enzyme responsible for the biosynthesis of the xenotransplantation antigen, namely pig alpha3 galactosyltransferase, has been studied by means of computational methods. Secondary structure predictions indicated that alpha3-galactosyltransferase and related protein family members, including blood group A and B transferases and Forssman synthase, are likely to consist of alternating alpha-helices and beta-strands. Fold recognition studies predicted that alpha3-galactosyltransferase shares the same fold as the T4 phage DNA-modifying enzyme beta-glucosyltransferase. This latter enzyme displays a strong structural resemblance with the core of glycogen phosphorylase b. By using the three-dimensional structure of beta-glucosyltransferase and of several glycogen phosphorylases, the nucleotide binding domain of pig alpha3-galactosyltransferase was built by knowledge-based methods. Both the UDP-galactose ligand and a divalent cation were included in the model during the refinement procedure. The final three-dimensional model is in agreement with our present knowledge of the biochemistry and mechanism of alpha3-Galactosyltransferases.
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Fold recognition study of alpha3-galactosyltransferase and molecular modeling of the nucleotide sugar-binding domain.
Glycobiology, 1999Co-Authors: Anne Imberty, Cédric Monier, Emmanuel Bettler, Solange Moréra, Paul S. Freemont, Manfred J. Sippl, Hannes Flöckner, Wolfgang Rüger, Christelle BretonAbstract:The structure and fold of the enzyme responsible for the biosynthesis of the xenotransplantation antigen, namely pig alpha3 galactosyltransferase, has been studied by means of computational methods. Secondary structure predictions indicated that alpha3-galactosyltransferase and related protein family members, including blood group A and B transferases and Forssman synthase, are likely to consist of alternating alpha-helices and beta-strands. Fold recognition studies predicted that alpha3-galactosyltransferase shares the same fold as the T4 phage DNA-modifying enzyme beta-glucosyltransferase. This latter enzyme displays a strong structural resemblance with the core of glycogen phosphorylase b. By using the three-dimensional structure of beta-glucosyltransferase and of several glycogen phosphorylases, the nucleotide binding domain of pig alpha3-galactosyltransferase was built by knowledge-based methods. Both the UDP-galactose ligand and a divalent cation were included in the model during the refinement procedure. The final three-dimensional model is in agreement with our present knowledge of the biochemistry and mechanism of alpha3-Galactosyltransferases.The structure and fold of the enzyme responsible for the biosynthesis of the xenotransplantation antigen, namely pig alpha3 galactosyltransferase, has been studied by means of computational methods. Secondary structure predictions indicated that alpha3-galactosyltransferase and related protein family members, including blood group A and B transferases and Forssman synthase, are likely to consist of alternating alpha-helices and beta-strands. Fold recognition studies predicted that alpha3-galactosyltransferase shares the same fold as the T4 phage DNA-modifying enzyme beta-glucosyltransferase. This latter enzyme displays a strong structural resemblance with the core of glycogen phosphorylase b. By using the three-dimensional structure of beta-glucosyltransferase and of several glycogen phosphorylases, the nucleotide binding domain of pig alpha3-galactosyltransferase was built by knowledge-based methods. Both the UDP-galactose ligand and a divalent cation were included in the model during the refinement procedure. The final three-dimensional model is in agreement with our present knowledge of the biochemistry and mechanism of alpha3-Galactosyltransferases.
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Sequence-Function Relationships of Prokaryotic and Eukaryotic Galactosyltransferases
Journal of biochemistry, 1998Co-Authors: Christelle Breton, Emmanuel Bettler, David H. Joziasse, Roberto A. Geremia, Anne ImbertyAbstract:Galactosyltransferases are enzymes which transfer galactose from UDP-Gal to various acceptors with either retention of the anomeric configuration to form alpha1,2-, alpha1,3-, alpha1,4-, and alpha1, 6-linkages, or inversion of the anomeric configuration to form beta1, 3-, beta1,4-, and beta1-ceramide linkages. During the last few years, several (c)DNA sequences coding for Galactosyltransferases became available. We have retrieved these sequences and conducted sequence similarity studies. On the basis of both the nature of the reaction catalyzed and the protein sequence identity, these enzymes can be classified into twelve groups. Using a sensitive graphics method for protein comparison, conserved structural features were found in some of the galactosyltransferase groups, and other classes of glycosyltransferases, resulting in the definition of five families. The lengths and locations of the conserved regions as well as the invariant residues are described for each family. In addition, the DxD motif that may be important for substrate recognition and/or catalysis is demonstrated to occur in all families but one.
Raquel Almeida - One of the best experts on this subject based on the ideXlab platform.
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identification and characterization of large galactosyltransferase gene families Galactosyltransferases for all functions
Biochimica et Biophysica Acta, 1999Co-Authors: Margarida Amado, Raquel Almeida, Tilo Schwientek, Henrik ClausenAbstract:Enzymatic glycosylation of proteins and lipids is an abundant and important biological process. A great diversity of oligosaccharide structures and types of glycoconjugates is found in nature, and these are synthesized by a large number of glycosyltransferases. Glycosyltransferases have high donor and acceptor substrate specificities and are in general limited to catalysis of one unique glycosidic linkage. Emerging evidence indicates that formation of many glycosidic linkages is covered by large homologous glycosyltransferase gene families, and that the existence of multiple enzyme isoforms provides a degree of redundancy as well as a higher level of regulation of the glycoforms synthesized. Here, we discuss recent cloning strategies enabling the identification of these large glycosyltransferase gene families and exemplify the implication this has for our understanding of regulation of glycosylation by discussing two galactosyltransferase gene families.
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Cloning and Expression of a Proteoglycan UDP-Galactose:β-Xylose β1,4-Galactosyltransferase I A SEVENTH MEMBER OF THE HUMAN β4-GALACTOSYLTRANSFERASE GENE FAMILY
The Journal of biological chemistry, 1999Co-Authors: Raquel Almeida, Steven B. Levery, Eric P. Bennett, Tilo Schwientek, Ulla Mandel, Hans Kresse, Henrik ClausenAbstract:Abstract A seventh member of the human β4-galactosyltransferase family, β4Gal-T7, was identified by BLAST analysis of expressed sequence tags. The coding region of β4Gal-T7 depicts a type II transmembrane protein with sequence similarity to β4-Galactosyltransferases, but the sequence was distinct in known motifs and did not contain the cysteine residues conserved in the other six members of the β4Gal-T family. The genomic organization of β4Gal-T7 was different from previous β4Gal-Ts. Expression of β4Gal-T7 in insect cells showed that the gene product had β1,4-galactosyltransferase activity with β-xylosides, and the linkage formed was Galβ1–4Xyl. Thus, β4Gal-T7 represents galactosyltransferase I enzyme (xylosylprotein β1,4-galactosyltransferase; EC 2.4.1.133), which attaches the first galactose in the proteoglycan linkage region GlcAβ1–3Galβ1–3Galβ1–4Xylβ1-O-Ser. Sequence analysis of β4Gal-T7 from a fibroblast cell line of a patient with a progeroid syndrome and signs of the Ehlers-Danlos syndrome, previously shown to exhibit reduced galactosyltransferase I activity (Quentin, E., Gladen, A., Roden, L., and Kresse, H. (1990) Proc. Natl. Acad. Sci. U. S. A. 87, 1342–1346), revealed two inherited allelic variants, β4Gal-T7186D and β4Gal-T7206P, each with a single missense substitution in the putative catalytic domain of the enzyme. β4Gal-T7186D exhibited a 4-fold elevated K m for the donor substrate, whereas essentially no activity was demonstrated with β4Gal-T7206P. Molecular cloning of β4Gal-T7 should facilitate general studies of its pathogenic role in progeroid syndromes and connective tissue disorders with affected proteoglycan biosynthesis.
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cloning of a novel member of the udp galactose β n acetylglucosamine β1 4 galactosyltransferase family β4gal t4 involved in glycosphingolipid biosynthesis
Journal of Biological Chemistry, 1998Co-Authors: Tilo Schwientek, Raquel Almeida, Steven B. Levery, Eric H. Holmes, Eric Bennett, Henrik ClausenAbstract:A novel putative member of the human UDP-galactose:beta-N-acetylglucosamine beta1,4-galactosyltransferase family, designated beta4Gal-T4, was identified by BLAST analysis of expressed sequence tags. The sequence of beta4Gal-T4 encoded a type II membrane protein with significant sequence similarity to other beta1,4-Galactosyltransferases. Expression of the full coding sequence and a secreted form of beta4Gal-T4 in insect cells showed that the gene product had beta1,4-galactosyltransferase activity. Analysis of the substrate specificity of the secreted form revealed that the enzyme catalyzed glycosylation of glycolipids with terminal beta-GlcNAc; however, in contrast to beta4Gal-T1, -T2, and -T3, this enzyme did not transfer galactose to asialo-agalacto-fetuin, asialo-agalacto-transferrin, or ovalbumin. The catalytic activity of beta4Gal-T4 with monosaccharide acceptor substrates, N-acetylglucosamine as well as glucose, was markedly activated in the presence of alpha-lactalbumin. The genomic organization of the coding region of beta4Gal-T4 was contained in six exons. All intron/exon boundaries were similarly positioned in beta4Gal-T1, -T2, and -T3. beta4Gal-T4 represents a new member of the beta4-galactosyltransferase family. Its kinetic parameters suggest unique functions in the synthesis of neolactoseries glycosphingolipids.
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A Family of Human β4-Galactosyltransferases CLONING AND EXPRESSION OF TWO NOVEL UDP-GALACTOSE:β-N-ACETYLGLUCOSAMINE β1,4-Galactosyltransferases, β4Gal-T2 AND β4Gal-T3
The Journal of biological chemistry, 1997Co-Authors: Raquel Almeida, Margarida Amado, Leonor David, Steven B. Levery, Eric H. Holmes, Gerard Merkx, Ad Geurts Van Kessel, Eske Rygaard, Helle Hassan, Eric P. BennettAbstract:BLAST analysis of expressed sequence tags (ESTs) using the coding sequence of the human UDP-galactose:β-N-acetylglucosamine β1,4-galactosyltransferase, designated β4Gal-T1, revealed a large number of ESTs with identical as well as similar sequences. ESTs with sequences similar to that of β4Gal-T1 could be grouped into at least two non-identical sequence sets. Analysis of the predicted amino acid sequence of the novel ESTs with β4Gal-T1 revealed conservation of short sequence motifs as well as cysteine residues previously shown to be important for the function of β4Gal-T1. The likelihood that the identified ESTs represented novel galactosyltransferase genes was tested by cloning and sequencing of the full coding region of two distinct genes, followed by expression. Expression of soluble secreted constructs in the baculovirus system showed that these genes represented genuine UDP-galactose:β-N-acetylglucosamine β1,4-Galactosyltransferases, thus designated β4Gal-T2 and β4Gal-T3. Genomic cloning of the genes revealed that they have identical genomic organizations compared with β4Gal-T1. The two novel genes were located on 1p32-33 and 1q23. The results demonstrate the existence of a family of homologous Galactosyltransferases with related functions. The existence of multiple β4-Galactosyltransferases with the same or overlapping functions may be relevant for interpretation of biological functions previously assigned to β4Gal-T1.
