Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Two different protein activators were isolated simultaneously from human liver for the enzymic hydrolysis of GM1 (Gal beta 1 leads to 3GalNAc beta 1 leads to 4Gal(3 comes from 2 alpha NeuAc)beta 1 leads to 4Glc-Cer) by beta-galactosidase and GM2 (GalNAc beta 1 leads to 4Gal(3 comes from 2 alpha NeuAc)beta 1 leads to 4Glc-Cer) by beta-hexosaminidase A. The hydrolysis of GM1 is stimulated only by the GM1-specific activator which has very little effect on the hydrolysis of GM2. The same is also true for the hydrolysis of GM2. The antiserum raised against GM1 activator did not cross-react with GM2 activator and vice versa. These results suggest the presence of two different activators for the separate hydrolysis of GM1 and GM2. In connection with the enzymic hydrolysis of GM1 and GM2, we found that the hydrolysis of GM2 by human hepatic beta-N-acetylhexosaminidase A was severely inhibited by a buffer of high ionic strength, whereas no such inhibition was observed in the hydrolysis of GM1 by beta-galactosidase.
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PMID:Evidence for the presence of two separate protein activators for the enzymic hydrolysis of GM1 and GM2 gangliosides. 11 63

A fucolipid that carried human blood group Lea activity was isolated from human small intestine. It contianed fucose, galactose, N-acetyl glucosamine, glucose, and ceramide in a molar ratio of 1:2:1:1:1. After periodate oxidation only 1 molecule of galactose and the N-acetylglucosamine remained. Permethylation of the lipid gave derivatives of a terminal fucose and galactose residue together with 2,4,6-tri-O-methylgalactose and 2,3,6-tri-O-methylglucose. After removal of fucose the lipid could be converted to a ceramide trihexoside with beta-galactosidase, and this, in turn, to ceramide lactoside by the action of beta-N-acetylhexosaminidase. Both enzymes converted the defucosylated derivative to a ceramide monohexoside. The methylated and the methylated and reduced derivatives of the intact lipid gave ions in mass spectrometry for a terminal hexose and deoxyhexose, a terminal trisaccharide of hexose, deoxyhexose and N-acetylhexosamine, and terminal tetra-and pentasaccharides. Ceramide fragments characteristic of hydroxy fatty acids with 16, 22, 23, and 24 carbons were found together with those of phytospingosine as the major long chain base. On the basis of these results and the immunologic activity of the fucolipid, the following structure is proposed: betaGal (1 leads to 3)betaGlcNAc (1 leads to 3)betaGal (1 leads to 4)Glc-ceramide alphaFuc (1 leads to 4).
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PMID:Characterization of a human intestinal fucolipid with blood group Lea activity. 16 7

The major beta-galactosidase of rabbit brain has been purified over 400-fold. The enzyme converts G-M-1-ganglioside; Gal beta-1 yields 3 GalNAc beta-1 yields 4 (NANalpha-2 yields 3) Gal beta-1 yields 4 Glc yields ceramide (G-M-1) into Tay Sachs ganglioside GalNAc beta-1 yields 4 (NANalpha-2 yields 3) Gal beta-1 yields 4 Glc yields ceramide (G-M-2-ganglioside) and ceramide lactoside, Gal beta-1 yields 4 Glc yields ceramide (Gal-Glc-Cer) into glucocerebroside, Glc yields ceramide (Glc-Cer). The enzyme also hydrolyzes the synthetic substrates NPh-Gal and MeUmb-Gal. It is eluted as a single peak from Sephadex G-200 columns when natural and synthetic substrates were used and has an isoelectric point of 6.3. We were unable to resolve activity towards G-M-1-ganglioside and Gal-Glc-Cer by polyacrylamide electrophoresis in two buffer systems. With G-M-1 the pH optimum was 4.3 in acetate buffer and the K-m value 78 mu-M while with Gal-Glc-Cer, a pH optimum of 4.5 and a K-m of 17 mu-M were found. Hydrolysis of both natural and synthetic substrates was inhibited by gamma-D-galactonolactone, D-galactose and lactose. The data strongly suggest that a single beta-galactosidase hydrolyzes all the substrates tested.
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PMID:Purification of G-M-1-ganglioside and ceramide lactoside beta-galactosidase from rabbit brain. 23 52

KB cells were synchronized by a double thymidine block procedure. An investigation was made of the activities of alpha-L-fucosidase (EC 3.2.1.51), alpha-D-galactosidase (EC 3.2.1.22), beta-D-galactosidase (ec 3.2.1.23), alpha-D-glucosidase (EC 3.2.1.20), beta-D-glucosidase (EC 3.2.1.21), alpha-D-mannosidase (EC 3.2.1.24), beta-D-N-acetylgalactosaminidase (EC 3.2.1.53), and beta-D-N-acetylglucosaminidase (EC 3.2.1.52) from synchronized cultures, using appropriate artificial substrates. Ceramide glucosidase (EC 3.2.1.45) and ceramide trihexosidase levels (EC 3.2.1.47) were also investigated at various stages in the cell cycle, using appropriate glycosphingolipid substrates. Whereas each of these enzymes exhibited some activity throughout the cell cycle, peak activity (2- to 6-fold increase) occurred late in the S phase. Two molecular forms of ceramide glucosidase (optimal activity at pH 4.0 and pH 6.0) and two forms of ceramide trihexosidase (pH 4.0 and pH 7.5) were identified. Peak levels of the forms that preferred the relatively acid pH occurred earlier in the S phase of the cell cycle than those of the forms that were more active at the higher pH. The possibility that the forms with optimal activity at pH 4 are precursors of those with optimal activity at pH 6 to 7.5 is discussed. Precipitation of beta-galactosidase of synchronized KB cells with specific antibody revealed that changes in the activity of this enzyme during the cell cycle were the result of fluctuations in the amount of the enzyme.
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PMID:Glycosphingolipid glycosyl hydrolases and glycosidases of synchronized human KB cells. 115 Jun 49

The presence and subcellular localization of UDP-Gal:glucosylceramide beta 1----4galactosyltransferase (GalT-2) was investigated in rat liver. For this purpose, purified Golgi apparatus, endoplasmic reticulum, and plasma membrane fractions were prepared from the liver and used as the enzyme source for detecting GalT-2. A pure Golgi apparatus, highly enriched in many glycosyltransferases, was the only fraction where GalT-2 was measurable. The reaction product formation rate under appropriate assay conditions, which requires high detergent concentration and Mn2+, was low but comparable with that of other glycosyltransferases. The product formation was stimulated by exogenously added acceptor GlcCer, donor UDP-Gal, and Golgi protein. The reaction product was a single spot that was identified by chromatographic behavior, sensitivity to beta-galactosidase, and permethylation studies as Gal beta 1----4Glc beta 1----1'Cer (lactosylceramide). A metabolic experiment, performed by determining the glycosphingolipids which became radioactive in the above subcellular fractions prepared from the liver of animals treated with glucose-labeled glucosylceramide, further indicated that the in vivo glycosylation of glucosylceramide takes place in the Golgi apparatus.
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PMID:Localization in the Golgi apparatus of rat liver UDP-Gal:glucosylceramide beta 1----4galactosyltransferase. 190 Apr 30

Methylation analysis of ceramide tetrasaccharide isolated from human erythrocytes gave acetates of 2,3,6-tri-O-methylgalactitol and 2,4,6-tri-O-methylgalactitol in a ratio of 1:1, and about 50% of the galactose was oxidized by periodate. Rat kidney ceramide tetrasaccharide gave, in contrast, a much larger proportion of the acetates of 2,4,6-tri-O-methylgalactitol (ratio 1:0.3), and less than 20% of the galactose was oxidized by periodate. Sequential degradation by beta-N-acetylhexosaminidase, alpha-galactosidase, and beta-galactosidase showed ceramide tetrasaccharides to have identical carbohydrate sequences and anomeric structures. The major part of ceramide trihexoside derived from rat kidney ceramide tetrasaccharide migrated on thin-layer chromatography more slowly than that derived from other ceramide tetrasaccharides. The structure of a major part of rat kidney ceramide tetrasaccharide was thus determined to be GalNAcbeta(1-->3)Galalpha(1-->3)Galbeta(1-->4)Glcbeta(1-->1)Cer, whereas other ceramide tetrasaccharides have Galalpha(1-->4) structure at the penultimate residue.
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PMID:Structures of ceramide tetrasaccharides from various sources: uniqueness of rat kidney ceramide tetrasaccharide. 434 27

A new procedure was developed for the isolation of long-chain, highly polar glycosphingolipids from human erythrocytes. The membrane material left after extraction of membrane lipids with organic solvents was peracetylated in a mixture of formamide, pyridine and acetic anhydride, and the acetylated products were then extracted with chloroform. The material was fractionated and purified by means of Sephadex LH-20, Sephadex LH-60 and silica-gel chromatography. The final preparations were mixtures of highly polar glycosphingolipids containing from 7 to 31 sugar residues relative to sphingosine. GC-MS analysis of the sugar part of the isolated fractions showed the presence of branched polyglycosyl chains of N-acetyllactosaminyl type. Endo-beta-galactosidase (Bacteroides fragilis) liberated from the deacetylated material two glycosphingolipids, which were identified by fast atom bombardment-mass spectrometry as Hex-Cer and HexNAc-Hex-Hex-Cer with sphingosine and mainly 24 and 22 carbon fatty acids. Endoglycoceramidase (Rhodococcus) degraded polyglycosylceramides to free ceramides and free polysaccharides. The released sugars were fractionated by high-pH ion-exchange chromatography into fractions differing in sialic acid content. The procedure presented in this paper can be used for large and small scale preparations of complex glycosphingolipids. It proved to be especially suitable for screening for polyglycosylceramides in different tissues.
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PMID:New method for the isolation of polyglycosylceramides from human erythrocyte membranes. 832 73

Sialoglycosphingolipids (gangliosides) are membrane components of eukaryotic cells that modulate cell signal transduction events. Discrepancies exist in the published descriptions of the gangliosides present in the human peripheral monocyte/macrophage. Macrophages were isolated from healthy human volunteers by two different methods. Their ganglioside fractions were isolated and examined by 2D thin-layer mobility, enzymatic susceptibility, and mass spectral-collision induced dissociation-mass spectral analyses. Thin-layer ganglioside chromatographic patterns displayed four major doublets and were similar for monocytes/macrophages isolated by either apheresis/elutriation or density gradient centrifugation. All gangliosides were resistant to beta-galactosidase but sensitive to Clostridium perfringens sialidase, indicating the absence of terminal galactose residues and sialidase-resistant sialic acid moieties. Mass spectra indicated only three major sets of glycolipid components with mass heterogeneity in the ceramide portion of each set. In all the gangliosides, the ceramide moiety contained only C18 sphingosine with the heterogeneity produced by the presence of C16 or C24 fatty acid. One doublet was resistant to Newcastle disease virus sialidase, indicating the presence of an alpha(2-6)-linked sialic acid residue with the same mass as another doublet. All data was consistent with the following structures as the major gangliosides of human peripheral monocyte/macrophages: II(3)NeuAcLacCer (sialolactosyl ceramide, GM3), IV(3)- and IV(6)NeuAcnLcOse(4)Cer (sialoparagloboside, nLM1), and IV(3)NeuAcnLcOse(6)Cer (a sialohexosylceramide).
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PMID:The major gangliosides of human peripheral blood monocytes/macrophages: absence of ganglio series structures. 1158 59

In mammalian tissues, the pathway known for the catabolism of G(M1) [Galbeta3GalNAcbeta4(Neu5Acalpha3)Galbeta4GlcCer; where Cer is ceramide] is the conversion of this ganglioside into G(M2) [GalNAcbeta4(Neu5Acalpha3)Galbeta4GlcbetaCer] by beta-galactosidase followed by the conversion of G(M2) into G(M3) (Neu5Acalpha3Galbeta4GlcbetaCer) by beta-N-acetylhexosaminidase A (Hex A). However, the question of whether or not G(M1) and G(M2) can also be respectively converted into asialo-G(M1) (Galbeta3GalNAcbeta4Galbeta4GlcCer; G(A1)) and asialo-G(M2) (GalNAcbeta4Galbeta4GlcbetaCer, G(A2)) by mammalian sialidases has not been resolved. This is due to the fact that sialidases purified from mammalian tissues always contained detergents that interfered with the in vitro hydrolysis of G(M1) and G(M2) in the presence of an activator protein. The mouse model of human type B Tay-Sachs disease created by the disruption of the Hexa gene showed no neurological abnormalities, with milder clinical symptoms than the human counterpart, and the accumulation of G(M2) in the brains of affected mice was only limited to certain regions [Sango, Yamanaka, Hoffmann, Okuda, Grinberg, Westphal, McDonald, Crawley, Sandhoff, Suzuki and Proia (1995) Nat. Genet. 11, 170-176]. These results suggest the possible presence of an alternative catabolic pathway (the G(A2) pathway) in mouse to convert G(M2) into G(A2) by sialidase. To show the existence of this pathway, we have used recombinant mammalian cytosolic sialidase and membrane-associated sialidase to study the desialylation of G(M1) and G(M2). We found that the mouse membrane-bound sialidase was able to convert G(M1) and G(M2) into their respective asialo-derivatives in the presence of human or mouse G(M2) activator protein. The cytosolic sialidase did not exhibit this activity. Our results suggest that, in vivo, the stable NeuAc of G(M1) and G(M2) may be removed by the mammalian membrane-associated sialidase in the presence of G(M2) activator protein. They also support the presence of the G(A2) pathway for the catabolism of G(M2) in mouse.
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PMID:Degradation of G(M1) and G(M2) by mammalian sialidases. 1169 12

Ceramide, a key molecule in sphingolipid metabolism and a candidate second messenger, has been shown to inhibit the activity of phospholipase D. This biochemical pathway has been implicated to regulate cell differentiation, apoptosis and cellular senescence. Ceramide is generated in response to a number of extracellular inducers(for example: TNF, IL-1 and Fas ligands etc.), and acts as a second messenger to mediate many of the effects of these inducers. HUVECs are the monolayer cells located inside the vein wall and play an important role in the regulation of vein physiology and blood function. It has been reported that the C6 ceramide can induce senescence of WI-38 HDF and promote the activity of beta-galactosidase, but, C2 ceramide has no such effect. In this study, we investigated the role of C6 ceramide in the senescence of HUVECs. 10 mumol/ml of C6 ceramide treatment for more than 72 hours can induce morphological alterations (such as: enlarged, flattened and irregular cell body), cell cycle arrested at G1 phase and the expression of the senescent histochemical marker-beta-galactosidase in HUVECs. These results showed that C6 ceramide could induce senescence-like changes of HUVECs. The detection of reactive oxygen species(ROS) and the anti-oxidative ability of the cells showed that the C6 ceramide induced senescence-like cells still have normal ability of anti-oxidation. Further investigations are ongoing.
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PMID:[Rapid induction of senescence-like changes in human umbilic vein endothelial cells(HUVECs) by C6 ceramide]. 1254 15


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