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:2.4.99.6 (sialyltransferase)
1,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have previously reported that ganglioside GM3 was remarkably increased during monocytoid differentiation of human myelogenous leukemia cell line HL-60 cells and that neolacto series gangliosides (NeuAc-nLc) were enriched during granulocytoid differentiation. In addition, HL-60 was differentiated into monocytic lineage by exogenous GM3 and into granulocytoid by NeuAc-nLc. In the present report, the enzymatic bases of glycosphingolipid biosynthesis in HL-60 during differentiation induced by 12-O-tetradecanoylphorbol-13-acetate and all-trans-retinoic acid were investigated. The following results were of particular interest. (i) Lactosylceramide alpha 2-->3 sialyltransferase (GM3 synthase) was remarkably up-regulated during monocyte differentiation, while the GM3 synthase level did not change in granulocytic differentiation. (ii) By contrast, lactosylceramide beta 1-->3N-acetylglucosaminyltransferase (Lc3Cer synthase) was down-regulated during monocytic differentiation, while the activity of Lc3Cer synthase was found to increase in granulocytic differentiation. (iii) The activities of four downstream glycosyltransferases (for synthesis of NeuAc-nLc) were found to increase or to remain unchanged during monocytic and granulocytic differentiation. These results strongly suggested the following. The dramatic GM3 increase and the decrease of NeuAc-nLc during monocytic differentiation are the consequences of the up-regulation of GM3 synthase and the down-regulation of Lc3Cer synthase, although the downstream enzymes are ready to catalyze their enzyme reactions. The notable increase of NeuAc-nLc and the relative decrease of GM3 during granulocytic differentiation are the results of the unchanged level of GM3 synthase and the up-regulation of Lc3Cer synthase together with the activation of the downstream glycosyltransferases. These results suggest that these two key upstream glycosyltransferases, GM3 synthase and Lc3Cer synthase, play critical roles in regulating the glycosphingolipid biosynthesis in HL-60 cells during differentiation. This switching mechanism of these two glycosyltransferases, together with our previous findings, might be one of the most important parts of the determining system of differentiation direction in human myeloid cells into monocytic or granulocytic lineages.
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PMID:Total metabolic flow of glycosphingolipid biosynthesis is regulated by UDP-GlcNAc:lactosylceramide beta 1-->3N-acetylglucosaminyltransferase and CMP-NeuAc:lactosylceramide alpha 2-->3 sialyltransferase in human hematopoietic cell line HL-60 during differentiation. 142 95

The acceptor specificities of four sialytransferases (I, II, IV and V) involved in ganglioside biosynthesis were studied in Golgi vesicles derived from rat liver. The activities of these sialytransferases were strongly detergent-dependent. Competition experiments with different detergent concentrations using LacCer (Gal beta 1----4Glc beta 1----1Cer), GM1a [Gal beta 1----3GalNAc beta 1----4(NeuAc alpha 2----3)Gal beta 1----4Glc beta 1----1Cer] and GD1b [Gal beta 1----3GalNAc beta 1----4(NeuAc alpha 2----8NeuAc alpha 2----3)Gal beta 1----4Glc beta 1----1Cer] as substrates, and as mutual inhibitors for ganglioside sialyltransferase activity, suggested that sialyltransferase IV was able to catalyze the sialyltransfer in alpha 2----3 linkage to the galactose residues of LacCer as well as of GM1a and GD1b. The other three sialyltransferases (I, II and V) seemed to be quite specific for their respective glycolipid acceptors, LacCer, GM3 and GM1b, GD1a and GT1b. Furthermore the kinetic data showed that sialyltransferase I was inactive at higher detergent concentrations (greater than 75 micrograms Triton CF-54); under these conditions, formation of GM3 and GD1a was catalyzed only by sialyltransferase IV. These results have been integrated into a model for ganglioside biosynthesis and its regulation.
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PMID:Substrate specificity of alpha 2----3-sialyltransferases in ganglioside biosynthesis of rat liver golgi. 199 63

A CMP-sialic acid: GM3 sialyltransferase (GD3 synthase) and a CMP-sialic acid: LacCer sialyltransferase (GM3 synthase) have been purified 10,000- and 3,000-fold, respectively, from the Triton X-100 extract of rat brain. The two enzymes were purified and resolved by affinity chromatography on two successive CDP-Sepharose columns by NaCl gradient elution. Final purification of GD3 synthase was achieved by specific elution from a 'GM3 acid'-Sepharose column with buffer containing GM3. Sodium dodecylsulfate-gel electrophoresis of GD3 synthase revealed a single major protein band with an apparent molecular weight of 55,000.
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PMID:Purification to homogeneity of GD3 synthase and partial purification of GM3 synthase from rat brain. 230 11

The patterns of acidic and neutral glycosphingolipids (GSLs) were examined in a syngeneic tumour system in Balb/c mice consisting of closely related cell lines with different colonisation potentials directed to the murine lungs (in vivo selected highly metastatic sublines of L1-fibrosarcoma cells and their WGA-resistant mutants with low metastatic potential). GSLs were analysed by high-performance thin-layer chromatography and structurally identified by fast atom bombardment mass spectrometry combined with compositional analyses and exo-glycosidase digestion. The results suggest that highly metastatic sublines L1-LM and L1-LM12 derived by in vivo selection from mouse fibrosarcoma cells (cell line L1) exhibit a drastic increase of polar ganglioside expression and a restriction to globo-series GSLs. Contrasting with this the low metastatic mutant cells (L1-LM13WGA) express a reduced portion of acidic GSLs and exhibit a shift to less polar ganglioside components. Total cellular and plasma membrane-integrated GSLs were demonstrated to exhibit largely identical patterns. Concomitant with a significant decrease in LacCer expression a substantial reduction of GM2 and a complete lack of GM3 expression can be assigned to the highly metastatic sublines of L1-cells. On the other hand, the more polar gangliosides GM1a and, to an even greater extent, GD1a (exceeding 70% of total gangliosides) accumulate on L1-LM and their clonal sublines. The shift to acidic GSLs of higher polarity is less pronounced on the low metastatic WGA-resistant mutant cells (L1-LM13WGA) showing a preponderance of GM1a. The portion of GD1a within the fractions of acidic GSLs does not correspond to the cellular activities of CMP-NeuAc/GM1 (alpha 2-3) sialyltransferase measured for high and low metastatic cell variants. Total sialic acid content of the various cell lines differs, but is not associated with the metastatic potential. Gangliosides on L1-cells exhibit a significant substitution of N-glycolyl for N-acetylneuraminic acid (13%) compared to their metastatic sublines and to mutant cells (less than 1%). A conversion of surface exposed GD1a to GM1a on membranes of metastatic cells by in situ treatment with Vibrio cholerae sialidase is associated with a significant reduction of tumour cell colonisation directed to the murine lungs.
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PMID:Glycosphingolipid expression on murine L1-fibrosarcoma cells: analysis of clonal in vivo and in vitro selected sublines with different lung colonisation potential. 237 82

We have shown previously that low density lipoproteins (LDL) suppressed the synthesis of lactosylceramide in normal human proximal tubular cells, but stimulated such synthesis in proximal tubular cells from LDL receptor negative subjects (Chatterjee, S., Clarke, K., and Kwiterovich, P.O., Jr. (1986) J. Biol. Chem. 261, 13474-13479). To understand the mechanism(s) of this effect of LDL, we have studied here the effects of LDL on the activity of UDP-GalCer:beta-galactosyltransferase (GalT-2). Maximum suppression (70-80%) of the activity of GalT-2 in normal proximal tubular cells at 37 degrees C occurred at a LDL concentration of 25 micrograms/ml medium. Such suppression was not observed either when the cells were incubated with LDL at 4 degrees C, or when the cells were preincubated with leupeptin, followed by incubation with LDL at 37 degrees C. High density lipoproteins and fetuin did not suppress the activity of GalT-2 in normal proximal tubular cells. In contrast LDL modified by reductive methylation (M-LDL, 100 micrograms/ml) stimulated the activity of GalT-2, approximately 3-fold. The effects of LDL and M-LDL were not related to their glycosphingolipid content. Much less suppression and stimulation of the activity of GalT-2 in proximal tubular cells by LDL and M-LDL, respectively, was found in normal human skin fibroblasts, Chinese hamster ovary cells, and bovine smooth muscle cells, suggesting that the LDL-mediated effect may be tissue-specific. In cells grown to very high density, the activity of the LDL receptor is decreased, and there was less suppression of GalT-2 activity by LDL. In normal proximal tubular cells, LDL stimulated the activity of UDP-Gal:LacCer, alpha-galactosyltransferase activity, UDP-Gal:LcOse3Cer, beta-galactosyltransferase, and CMP-NeuAc:LacCer,alpha-sialyltransferase activity but did not alter the activity of sulfotransferase. In conclusion, LDL that entered the normal proximal tubular cells via the LDL receptor-mediated pathway decreased GalT-2 activity, an effect that was dependent upon the binding, internalization, and degradation of receptor-bound LDL. In contrast LDL that entered normal or LDL receptor-negative proximal tubular cells via an LDL receptor-independent pathway failed to suppress GalT-2 activity, and led to a stimulation of LacCer synthesis.
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PMID:Regulation of glycosphingolipid glycosyltransferase by low density lipoprotein receptors in cultured human proximal tubular cells. 245 39

Sialyltransferase-1 activity was studied in cultured 12-18 human glioma cells. The apparent Km and Vmax with variable LacCer concentrations were 32 microM and 197 pmoles/mg protein/hr and with variable CMP-NeuAc concentrations were 172 microM and 877 pmoles/mg protein/hr., respectively. The pH optimum towards exogenous LacCer was 6.0 and towards endogenous acceptors was 6.2. The optimum protein:detergent ratio was 1:1. Human beta interferon (1000 units/ml medium) increased sialyltransferase-1 activity only slightly on a protein basis but increased it 47% on a per cell basis. These results demonstrate that one of the biochemical effects of beta-interferon on 12-18 human glioma cells is to stimulate ganglioside synthesis.
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PMID:Sialyltransferase-1 in a human malignant glioma cell line. Kinetic characteristics and effect of human interferon-beta. 285 19

Changes in the composition and metabolism of glycosphingolipid (GSL), which is one of the cell surface constituents, during cell differentiation of human T-lymphoblastic leukemia cell line MOLT-3 cells were examined with special reference to their alterations in E rosette-forming capacity and expression of surface antigens specific for T-cell lineage. Three molecular species of neutral GSL and greater than or equal to 13 molecular species of acidic sialosyl-GSL (ganglioside) were detectable on high-performance thin-layer chromatography (HPTLC) in untreated MOLT-3 cells. The major components were ceramide monohexoside and gangliosides GM3 and GD1a. When the cells were induced by 12-O-tetradecanoyl phorbol 13-acetate (TPA) to differentiate into more mature T cells, the ganglioside composition changed distinctively, and the total ganglioside content increased considerably; mono-, di-, and tri-sialosyl gangliosides concomitantly showed significant increase, but no new molecular species of GSL specific for the differentiation were detected. The activity of one sialyltransferases, CMP-sialic acid:CDH sialyltransferase, which synthesizes ganglioside GM3 and the total sialic acid content of the cell surface, parallelled the extent of cell differentiation. Examination of another human T-lymphoblastic leukemia cell line, HPB-ALL, indicated that TPA could also induce the cells to differentiate along T-cell lineage and that changes in the ganglioside pattern during differentiation are similar to those of MOLT-3 cells. The results indicate that human T-lymphoid cell differentiation intimately involves elongation of neutral oligosaccharide-moieties and the addition of sialic acid residues to gangliosides, resulting in more mature T cells containing higher gangliosides. Both the sialyltransferase activity and the sialic acid content, as well as the ganglioside pattern, might be new biochemical markers specific for human T-lymphoblastic cell differentiation.
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PMID:Neutral and sialosyl glycosphingolipid composition and metabolism of human T-lymphoblastic cell line MOLT-3 cells: distinctive changes as markers specific for their differentiation. 326 Nov 82

The effects of phytohemagglutinin (PHA) stimulation on the activities of sialyltransferase 1 (SAT-1), and sialyltransferase 3 (SAT-3), in human lymphocytes were investigated in vitro. For SAT-1 and SAT-3, respectively, the apparent Km values with variable CMP-NeuAc concentrations were 0.19 and 0.015 mM and with variable LacCer were 0.075 and 0.17 mM. Progressive increases in the activities of SAT-1 and SAT-3 were detected in lymphocytes stimulated with PHA, whereas no increase was observed in control lymphocytes incubated in culture medium alone. These increased activities occurred within 18-36 h of incubation and preceded optimum lymphocyte proliferation. Intact lymphocytes were needed for the lectin-stimulated increase of sialyltransferase activities because neither concanavalin A nor phytohemagglutinin added to the broken cell preparation modulated SAT-1 activity. The glycolipid products formed as a result of these enzymatic reactions in the presence of endogenous and exogenous acceptors were tentatively identified by thin-layer chromatography and autofluorography. The addition of exogenous LacCer to the SAT-1 assay resulted in the radiolabeling of a small amount of ganglioside GM1b (3.4%), but GM3 was the major labeled product (96%). When GgOse4Cer was added to the SAT-3 assay, 32% GM3 and 24.6% GM1b were detected while 44% consisted of glycolipids not labeled in assays performed without exogenous acceptors. Of the radioactivity transferred to endogenous acceptors, 81.3% was in GM3 and 14.6% in GM1b. These results demonstrate that the modulation of sialyltransferase activity occurs earlier than cellular activation.
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PMID:Effects of lectin activation on sialyltransferase activities in human lymphocytes. 371 65

Human fibroblast cell line WI-38 cultured in vitro was treated with a human recombinant IL-4 at concentrations of 1 to 100 U/ml to examine the alteration of glycosphingolipid (GSL) expression of the cells. Neutral GSL of non-treated WI-38 cells consisted of CMH (GlcCer), CDH, CTH, and Gb4Cer; CMH and CTH were the major components. The acidic GSL were composed of GM3 as the predominant component and other minor gangliosides including GD3. The neutral GSLs did not change in profile during the treatment with IL-4, while the acidic GSLs showed a prominent change, an increase of GD3 content. The increase of GD3 was detectable with IL-4 concentrations over 1 U/ml, and reached a plateau at 10 U/ml, where the amount of GD3 was almost equal to that of GM3. The GD3 increase occurred at 24 h after the IL-4 treatment, and lasted for at least 96 h, as long as IL-4 remained present in the culture media. The GD3 synthase (sialyltransferase) level was found to be increased in an IL-4 dose-dependent manner. IL-4 did not influence the growth or morphological appearance of WI-38 cells. The results demonstrate a novel biological effect of IL-4, modulating GSL in non-hematopoietic cells.
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PMID:Interleukin 4 enhances ganglioside GD3 expression on the human fibroblast cell line WI-38. 760 18

The composition of tissue gangliosides is thought to result mainly from the active regulation and selective expression of specific enzymes responsible for their metabolism. In the last few years, we have purified several rat brain sialyltransferases to homogeneity; the availability of these highly purified enzymes enabled us to investigate their regulation and expression at the molecular level. Thus, we studied the regulation of sialyltransferase activities, in particular, CMP-NeuAc:GM1 and CMP-NeuAc:LacCer sialyltransferases by a phosphorylation/dephosphorylation mechanism. Protein kinase C was added to a standard enzyme assay mixture containing [gamma-32P]ATP, and the activity of the enzyme was measured after various incubation times. We found that treatment of several sialyltransferases by protein kinase C decreased their activities in a time-dependent manner. Analyses of 32P-labeled amino acids revealed that the major phosphorylation site of CMP-NeuAc:GM1 alpha 2-->3 sialyltransferase (ST-IV) was serine and that for CMP-NeuAc:LacCer alpha 2-->3 sialyltransferase (ST-I) was primarily threonine. Partial recovery of the enzyme activity could be achieved by treatment of the phosphorylated sialyltransferases with rat brain protein phosphatase. We conclude that the activities of sialyltransferases can be modulated by protein kinase C and protein phosphatase and this may represent a potential regulatory mechanism for ganglioside biosynthesis.
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PMID:Regulation of sialyltransferase activities by phosphorylation and dephosphorylation. 772 15


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