Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The synthesis of glycoproteins containing N-linked complex oligosaccharides is blocked by swainsonine at the step catalyzed by Golgi mannosidase II (Tulsiani, D. R. P., Harris, T. M., and Touster, O. (1982) J. Biol Chem. 257, 7936-7939). Accordingly, hybrid glycoproteins might be produced in the presence of swainsonine. In this report, we demonstrate that swainsonine causes human skin fibroblasts to synthesize such glycoproteins. In control fibroblasts, there were approximately equal amounts of complex and high mannose glycoproteins. In the presence of swainsonine (10 micrograms/ml), most of the complex glycoproteins were replaced by hybrid types. The principal oligosaccharide had the following structure: (formula; see text) A smaller amount of the asialo hybrid was also produced. The structure of the hybrid was established by Bio-Gel P-4 fractionation of oligosaccharides produced by endoglycosidase H treatment of pronase-derived glycopeptides, followed by examination of the susceptibility of the oligosaccharide to glycohydrolases and by its adsorbability to serotonin-Sepharose 4B. The same hybrid oligosaccharide was produced efficiently by rat liver Golgi membranes in the presence of ([3H] Man)5GlcNAc, UDP-GlcNAc, UDP-Gal, CMP-NeuAc, and swainsonine. Golgi mannosidase II had no action on the hybrid oligosaccharide, and little action on asialo hybrid, but both were converted to the mannosidase II substrate, GlcNAcMan5GlcNAc, by appropriate treatment with neuraminidase and beta-galactosidase. Jack bean alpha-D-mannosidase gave the expected yields of free mannose from the various oligosaccharides studied in this work. Swainsonine should be useful in investigating the role of oligosaccharide structure of glycoproteins because of its ability to alter the oligosaccharide.
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PMID:Swainsonine causes the production of hybrid glycoproteins by human skin fibroblasts and rat liver Golgi preparations. 640 79

In previous studies on glycosyltransferase activities in porcine trachea, we demonstrated the presence of two galactosyltransferases which transfer galactose from UDP-galactose to N-acetylglucosamine (Sheares, B.T. and Carlson, D.M. (1983) J. Biol. Chem. 258, 9893-9898). One enzyme, UDP-galactose:N-acetylglucosamine 3 beta-galactosyltransferase, synthesized galactosyl-beta 1,3-N-acetylglucosamine while the other, UDP-galactose:N-acetylglucosamine 4 beta-galactosyltransferase, synthesized galactosyl-beta 1,4-N-acetylglucosamine. A third galactosyltransferase has now been demonstrated utilizing a solubilized membrane preparation from pig trachea, which also synthesizes galactosyl-beta 1,4-N-acetylglucosamine as determined by gas-liquid chromatography and Diplococcus pneumoniae beta-galactosidase treatment. This new UDP-galactose:N-acetylglucosamine 4 beta-galactosyltransferase is distinct from the lactose synthetase A protein in that it does not bind to alpha-lactalbumin-agarose or to N-acetylglucosamine-agarose. The enzyme is separable from the UDP-galactose:N-acetylgalactosaminyl-mucin 3 beta-galactosyltransferase by affinity chromatography on asialo ovine submaxillary mucin adsorbed to DEAE-Sephacel. This newly discovered 4 beta-galactosyltransferase binds to UDP-hexanolamine-Sepharose and is partially separated from UDP-galactose:N-acetylglucosamine 3 beta-galactosyltransferase by Sephacryl S-200 gel filtration chromatography. Neither high concentrations of N-acetylglucosamine (200 mM) nor alpha-lactalbumin inhibits the incorporation of galactose into galactosyl-beta 1,4-N-acetylglucosamine by this enzyme.
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PMID:Two distinct UDP-galactose: 2-acetamido-2-deoxy-D-glucose 4 beta-galactosyltransferases in porcine trachea. 642 38

Sepharose 4B-immobilized desialylated ovine submaxillary mucin was used as an acceptor for galactose transfer from UDP-galactose, catalyzed by a Triton X-100-solubilized galactosyltransferase from human erythrocyte ghosts. The product could be cleaved from the insoluble acceptor substrate by alkaline borohydride treatment and identified on Bio-Gel P-2 as a disaccharide. The nature of the glycosidic bond of the isolated material was elucidated by periodate oxidation/NaB[3H]4 reduction/acid hydrolysis and subsequent identification of the aminopolyol formed as L-threosaminitol. Specific cleavage of the enzymatic product by beta-galactosidase indicated a beta-configuration for incorporated galactose. These data permit classification of the enzyme as UDP-galactose: alpha-D-N-acetylgalactosaminyl-protein beta (1 leads to 3) transferase. Furthermore, in the presence of Triton X-100, the enzyme from normal erythrocytes catalyzed transfer of galactose to the glycan moieties of asialo-agalacto-glycophorin in Tn-erythrocytes from a patient with permanent mixed-field polyagglutinability.
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PMID:Identification of the product formed by human erythrocyte galactosyltransferase. 678 80

We have characterized the UDP-galactose: alpha-N-acetylgalactosaminide beta 3 galactosyltransferase in human tracheal epithelium using asialo ovine submaxillary mucin as the acceptor. Maximal enzyme activity was obtained at pH 6.0-7.5 and at 20-25 mM MnCl2 and at 2% Triton X-100. Cd2+ could substitute for Mn2+ as the divalent ion cofactor. Spermine, spermidine, putrecine, cadaverine, and poly-L-lysine stimulated the enzyme activity at low (2.5 mM) MnCl2 concentration. The apparent Michaelis constants for N-acetylgalactosamine, asialo ovine submaxillary mucin, and UDP-galactose were 15.5, 1.14, and 1.36 mM, respectively. The enzyme activity was not affected by alpha-lactalbumin. The alpha-N-acetygalactosaminide beta 3 galactosyltransferase was shown to be different from the N-acetylglucosamine galactosyltransferase by acceptor competition studies. The product of galactosyltransferase was identified as Gal beta 1 leads to 3GalNAc alpha Ser (Thr) by (a) isolation of [14C]Gal-GalNAc-H2 after alkaline borohydride treatment of the 14C-labeled product, (b) establishment of the beta-configuration of the newly synthesized glycosidic bond by its complete cleavage by bovine testicular beta-galactosidase, and (c) assignment of the 1 leads to 3 linkage by identification of threosaminitol obtained from the oxidation of the disaccharide with periodic acid followed by reduction with sodium borohydride, hydrolysis in 4 N HCl, and analysis on an amino acid analyzer. The 1 leads to 3 linkage was confirmed by its resistance to jack bean beta-galactosidase and by the presence of a m/e 307 ion fragment and the absence of a m/e 276 ion by gas-liquid chromatography-mass spectrometry analysis. When acid and beta-galactosidase-treated human tracheobronchial mucin was used as the acceptor, 3.3% of the product was found as [14C]Gal-GalNAc-H2. The remainder of the [14C]Gal was found in longer oligosaccharides formed by a different beta-galactosyltransferase. This galactosyltransferase is slightly inhibited by alpha-lactalbumin and stimulated by spermine.
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PMID:Mucin biosynthesis. Characterization of UDP-galactose: alpha-N-acetylgalactosaminide beta 3 galactosyltransferase from human tracheal epithelium. 680 62

1. myo-Inositol was galactosylated by UDP-galactose in the presence of alpha-lactalbumin plus rat mammary Golgi membranes enriched in galactosyltransferase (EC 2.4.1.22). 2. The isolated product migrated on GLC as two peaks of material, apparently identical to galactinol (galactosylinositol) isolated from rat milk. 3. These findings make it likely that in vivo lactose synthetase is responsible for converting inositol into galactinol within the Golgi lumen. 4. This is consistent with the ability of inositol to penetrate the Golgi membrane in vitro, and renders less likely a previously proposed role of beta-galactosidase (EC 3.2.1.23) in mammary galactinol synthesis.
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PMID:Biosynthesis of galactinol by lactose synthetase. 680 5

A high galactosyltransferase activity with lactotriaosylceramide as acceptor has been found in human serums. The reaction requires UDP-galactose, Mn2+, and Triton X-100. It has a pH optimum of 6.0 and a Km for lactotriaosylceramide of 0.66 mM. On the basis of methylation analysis and susceptibility towards beta-galactosidase the reaction product has been identified as neolactotetraosylceramide. Lactotetraosylceramide formation was not observed. Evidence is presented that the serum enzymic activity can be attributed to N-acetyllactosamine synthase (EC 2.4.1.90). The beta 1 leads to 4-galactosyltransferase activities with lactotriaosylceramide as acceptor have been determined in different human sera. The activity is independent of ABO, p and Rh blood-group status. The enzyme is within a normal range in serums of cancer patients.
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PMID:Enzymatic synthesis of neolactotetraosylceramide by the N-acetyllactosamine synthase of human serum. 681 Dec 67

Past studies have suggested that mouse sperm surface galactosyltransferase may participate during fertilization by binding N-acetylglucosamine (GlcNAc) residues in the zona pellucida. In this paper, we examined further the role of sperm surface galactosyltransferase in mouse fertilization. Two reagents that specifically perturb sperm surface galactosyltransferase activity both inhibit sperm-zona binding. The presence of the milk protein alpha-lactalbumin specifically modifies the substrate specificity of sperm galactosyltransferase away from GlcNAc and towards glucose and simultaneously inhibits sperm binding to the zona pellucida. Similarly, UDP-dialdehyde inhibits sperm binding to the zona pellucida and sperm surface galactosyl-transferase activity to identical degrees. Of five other sperm enzymes assayed, four are unaffected by UDP-dialdehyde, and one is affected only slightly. Covalent linkage of UDP-dialdehyde to sperm dramatically inhibits binding to eggs, while treatment of eggs with UDP-dialdehyde has no effect on sperm binding. Heat-solubilized or pronase-digested zona pellucida inhibit sperm-zona binding, and they can be glycosylated by sperm with UDP-galactose. Sperm are also able to glycosylate intact zona pellucida with UDP-galactose. Thus, solubilized and intact zona pellucida act as substrates for sperm surface GlcNAc:galactosyltransferases. Finally, pretreatment of eggs with beta-N-acetylglucosaminidase inhibits sperm binding by up to 86%, while under identical conditions, pretreatment with beta-galactosidase increases sperm binding by 55%. These studies, in conjunction with those of the preceding paper dealing with surface galactosyltransferase changes during capacitation, directly suggest that galactosyltransferase is at least one of the components necessary for sperm binding to the zona pellucida.
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PMID:A role for mouse sperm surface galactosyltransferase in sperm binding to the egg zona pellucida. 681 12

Serum resistance of gonococci in most patients is due to sialylation of a Gal beta 1-4GlcNAc group on a conserved 4.5 kDa lipopolysaccharide (LPS) component by host cytidine 5'-monophospho-N-acetyl neuraminic acid (CMP-NANA) catalysed by a gonococcal sialyl transferase. This sialylation is enhanced by a low M(r) factor(s) which, like CMP-NANA, is released in diffusates from high M(r) fractions obtained from sonicates dialysed at 4 degrees C. Also, as shown here, this factor(s) is released when the sonicates are dialysed at 18-20 degrees C. The enhancement of sialylation, first demonstrated using enzymes in gonococcal extracts, has been shown to occur in live gonococci and hence probably to have a role in pathogenicity. Gonococci, emerging from lag phase and incubated for 2 h with CMP-14CNANA fixed up to 90% more radiolabel than controls when the second factor(s) was present; their LPS separated by SDS-PAGE contained more radiolabel than control samples and label was not detected in any other component. Fractions with enhancing activity absorbed maximally at about 260 nm but a mixture of UDP-galactose (UDP-Gal), UDP-N-Acetyl galactosamine (UDP-GalNAc), UDP-glucose (UDP-Glc) and UDP-N-Acetyl glucosamine (UDP-GlcNAc) showed no significant enhancing activity. The enhancing action of the low M(r) fractions was unaffected by incubation with beta-galactosidase.
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PMID:Sialylation of lipopolysaccharide by CMP-NANA in viable gonococci is enhanced by low Mr material released from blood cell extracts but not by some UDP sugars. 783 May 28

An assay method was devised for measuring the activity of galactosyltransferase I (UDP-D-galactose:D-xylose galactosyltransferase), which is one of the enzymes synthesizing the linkage region between the core protein and glycosaminoglycan chains of proteoglycan. For this method, the reaction mixture contained a fluorescent substrate, 4-methylumbelliferyl-beta-D-xyloside as an acceptor, UDP-galactose as a donor and D-galactal as a competitive inhibitor of endogenous beta-galactosidase in the enzyme solution. The reaction mixture was incubated at 37 degrees C with enzyme solution prepared from an extract of cultured cells, and galactosyl-xylosyl-4-methylumbelliferone was produced as a reaction product. Measurement of galactosyltransferase I activity was performed by separation and quantitative analysis of this reaction product using high-performance liquid chromatography. Utilizing this method, easier and more sensitive detection of galactosyltransferase I activity in a cell-free system became possible. Application of the method revealed that cultured human skin fibroblasts contained galactosyltransferase I activity.
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PMID:A method for determination of galactosyltransferase I activity synthesizing the proteoglycan linkage region. 783 58

Somatic mutations and drugs that either reduce beta 1-6GlcNAc-branching of N-linked oligosaccharides or block the addition of terminal sequences containing galactose and sialic acid have been shown to inhibit tumour growth and metastasis. In an attempt to further define the oligosaccharide sequences that contribute to the malignant phenotype, we have selected spontaneous wheat germ agglutinin-resistant (WGAR) mutants from highly metastatic murine lymphoid tumour cells and characterized four mutant phenotypes. Mutants were selected from VM4, a clone of the MDAY-D2 tumour cell line which had been transfected with the bacterial beta-galactosidase gene (LacZ). VM4 cells retained the malignant phenotype of MDAY-D2 and the cells expressed LacZ, which facilitated the counting of metastases as the tumour cells stained blue when incubated with 5-bromo-4-chloro-3-indolyl beta-D-galactopyranoside (X-gal). The most frequently isolated mutant was defective in the transport of UDP-Gal into the Golgi, and as previously observed for this mutation, the cells were non-metastatic and produced very slow-growing solid tumours. Mutants expressing CMP-SA hydroxylase, and consequently glycoconjugates with N-glycolylneuraminic acid (NeuNGc), remained highly metastatic, but grew more slowly than VM4 cells as s.c. tumours in mice. A novel WGAR mutant showing a large increase in Gal beta 1-4GlcNAc:alpha 2-6 sialyltransferase (SA-T) mRNA levels (ST6N) and enzyme activity was observed to be less metastatic and also grew more slowly at the s.c. site of inoculation. Finally, a fourth phenotypic class of WGAR mutants showed a complex phenotype including expression of a beta Gal-binding cell surface lectin and reduced sialylation of glycoconjugates. These results suggest that changes in either the amount, the type or linkage of sialic acid in tumour cell glycoconjugates can affect tumour growth and metastasis.
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PMID:Sialylation and malignant potential in tumour cell glycosylation mutants. 788 Nov 81


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