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:2.4.99.7 (sialyltransferase)
1,534 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A serum B12-binding protein with increased sialic acid content (termed hepatoma B12-binding protein) that causes elevations of serum B12 and unsaturated B12-binding capacity has been found in some patients with hepatocellular carcinoma (hepatoma). We now report another patient with hepatoma with initial near-normal, unsaturated B12-binding capacity that increased 400-fold as the disease progressed and then fell 50% with response to chemotherapy. A perfusate of the tumor in the liver had 5 times more B12-binding protein than did the serum and was immunologically the same as the serum hepatoma B12-binding protein isolated from previous cases. A cell line derived from hepatoma produced significant amounts of B12-binding protein similar to hepatoma B12-binding protein, whereas cell lines from normal liver and other neoplasia did not. The hepatoma sera, perfusate, and media from the hepatoma cell line contained elevated sialyltransferase activity. These data suggest that some hepatomas produce increased hypersialylated B12-binding protein that is cleared slowly from the plasma and accumulates there as hepatoma B12-binding protein.
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PMID:The clinical and physiological implications of hepatoma B12-binding proteins. 6 88

The following three parameters were studied in Morris hepatomas of different growth rates: (a) the specific activity of guanosine dephosphate (GDP)-fucose:glycoprotein fucosyltransferase and cytidine monophosphate (CMP)-N-acetylneuraminic acid:glycoprotein sialyltransferase, (B) the content of GDP-fucosee and CMP-N-acetylneuraminic acid, and (c) the activity of alpha-L-fucosidase and neuraminidase. Fucosyltrasferase activities were significantly elevated in all hepatomas investigated. Especially high levels of enzyme were measured in the rapidly growing tumors 7777, 66, and 3924A. The increase varied between 2- and 3-fold when compared with the corresponding host liver. Conversely, the activity of the sialytransferase was greatly decreased in all hepatoma lines with a rapid or intermediate growth rate. In the fast-growing tumor 9618A2, the activity was reduced to 8%. GDP-fucose and CMP-N-acetylneuraminic acid were determined by the isotope dilution technique. In normal rat liver from Buffalo or ACl rats, the concentration of GDP-fucose was 6.5+/-0.9 and 9.5+/-1.1nmoles/g, wet weight, respectively. In the fast-growing hepatomas 3924A and 9121, levels up to 21.5 nmoles/g, wet weight, were found, However, the content of CMP-N-acetylneuraminic acid in hepatomas was indluenced to a lesser extent by the degree of differentiation of the tumor. In the most rapidly growing tumor, 9618A2, a level of alpha-L- fucosidase seven times higher than in host liver was determined. Moreover, there existed a correlation bewteen the age of the hepatoma and enzyme activity. Within the 2nd week after inoculation, fucosidase activity increased from 130 to 343 nmoles/hr/mg of protein. Neuraminidase was measured in a new linked assay system. The activity of this enzyme was lowered by 50% or was at least unchanged when compared to the activity in host liver. Our results indicate that specific alterations of fucose metabolism are a characteristic feature of Morris hepatomas.
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PMID:Glycosyltransferases and glycosidases in Morris hepatomas. 19 53

Sialyltransferase (EC 2.4.99.1) is released in large amounts by two hepatoma cell lines (SK-H-MA and CLH) established from patients with hepatocellular carcinoma (hepatoma). This release requires protein synthesis and glycoprotein synthesis, but not cell division. In contrast, sialyltransferase is released in minimal amounts by a cell line derived from normal human liver (Chang). The hepatoma cells also contain more surface and cellular sialyltransferase activity than Change cells. Hepatoma sialyltransferase has properties similar to other sialyltransferases. Using a calibrated Sephadex G-200 column, it is resolved into two forms with molecular weights of 65 000 and 80 000.
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PMID:The specific release of sialytransferase activity by human hepatoma cell lines. 22 27

We investigated biosynthesis, intracellular transport and release of beta-galactoside alpha-2,6-sialyltransferase in a dexamethasone-inducible rat hepatoma cell line. Confluent cells were induced by 10 microM dexamethasone for 24 h, and metabolically labelled with [35S]methionine/cysteine, followed by immunoprecipitation of sialyltransferase and electrophoretic/fluorographic analysis. The 35S-labelled enzyme was synthesized as a 46-kDa precursor, converted to an intermediate 47-kDa form after 1 h, and gradually to a mature form of 48 kDa within the following 3 h. By means of either tunicamycin inhibition of N-glycosylation or cleavage of N-glycans from isolated sialyltransferase using N-glycosidase F, the sizes of the precursor and the mature form were reduced to 41 kDa and 43 kDa, respectively. After a 4-h chase, treatment with endoglycosidase H revealed two distinct molecular forms of sialyltransferase, bearing either two N-acetyllactosamine-type or one oligomannose-type and one N-acetyllactosamine-type N-linked sugar chain. In addition, sialyltransferase became sensitive to neuraminidase digestion after a 4-h chase. The half-life of intracellular [35S]sialyltransferase was estimated at 3 h. A soluble form was detectable in the supernatant, 2 h after the pulse. Only 12% of the initially labelled sialyltransferase was found in the medium after 12 h, while 73% of the enzyme was degraded intracellularly. To characterize a possible intracellular degradation site, we studied intracellular transport in the presence of either secretion-blocking or acidotropic agents or protease inhibitors. Degradation was significantly delayed by all treatments. Our results show that sialyltransferase follows the secretory pathway as a membrane protein and is retained at a late Golgi stage. We suggest that the bulk of sialyltransferase in rat hepatoma cells is diverted to a post-Golgi degradation pathway. This route contrasts with the post-Golgi trafficking of beta-1,4-galactosyltransferase in HeLa cells, which is constitutively secreted [Strous, G. J. A. M. & Berger, E. G. (1982) J. Biol. Chem. 257, 7623-7628].
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PMID:Biosynthesis and intracellular transport of alpha-2,6-sialyltransferase in rat hepatoma cells. 152 30

Glycosyltransferase activities of highly purified fractions of Golgi apparatus, plasma membrane and endoplasmic reticulum, all from the same homogenates, were analyzed and compared. Additionally, Golgi apparatus were unstacked and the individual cisternae separated into fractions enriched in cis, median and trans elements using the technique of preparative free-flow electrophoresis. Golgi apparatus from both liver and hepatomas were enriched in all glycosyltransferases compared to endoplasmic reticulum and plasma membranes. However, Golgi apparatus from hepatomas showed both elevated fucosyltransferase and galactosyltransferase activities but reduced sialyltransferase and dipeptidyl peptidase IV (DPP IV) activities compared to liver. Activity of N-acetylglucosaminyltransferase was approximately the same in both liver and hepatoma Golgi apparatus. With normal liver, sialyl- and galactosyltransferase activities and DPP IV showed a marked cis-to-trans gradient of activity. Fucosyltransferase was concentrated in two regions of the electrophoretic separations, one corresponding to cis cisternae and one corresponding to trans cisternae. N-Acetylglucosaminyltransferase activity was more widely distributed but the endogenous acceptor activity was predominantly cis. With hepatoma Golgi apparatus, the pattern for DPP IV was similar to that for liver but those of sialyl- and galactosyltransferases differed markedly from liver. Instead of activity increasing cis to trans, the activities for sialyl- and galactosyltransferases decreased. For fucosyltransferases, activity dependent on exogenous acceptor was medial whereas with endogenous acceptor, two activity peaks, cis and trans, still were observed. For N-acetylglucosaminyltransferase the pattern for hepatoma was similar to that for liver. The results indicate alterations in the distribution of glycosyltransferase activities within the Golgi apparatus in hepatotumorigenesis that may reflect altered cell surface glycosylation patterns.
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PMID:Distribution of glycosyltransferases among Golgi apparatus subfractions from liver and hepatomas of the rat. 168 14

The gangliosides of human hepatoma biopsies, human hepatoma cell lines, and diethylnitrosamine-induced rat hepatomas were examined. These malignant tissues all expressed increased content of disialolactosylceramide (GD3) with respect to their normal counterparts. During the induction of rat hepatoma by diethylnitrosamine, an increase in GD3 levels appeared as early as 12 wk after initiation of diethylnitrosamine, concurrent with the appearance of precancerous hepatocytes. GD3 levels gradually increased to a peak of 4 times that of normal rat liver at 20 wk. CMP-NeuAc:GM3 sialyltransferase, the enzyme that synthesizes GD3 by transfer of sialic acid to GM3, also had tumor-associated elevation during the course of diethylnitrosamine-induction of rat hepatomas. To investigate the relationship of oncogene transformation and changes in ganglioside biosynthesis, NIH 3T3 cells transfected DNAs from human hepatoma or nasopharyngeal carcinoma were studied. The transfectants each expressed the same ganglioside composition, including a detectable level of GD3, as well as enhanced activity of CMP-NeuAc:GM3 sialyltransferase. A correlation between the tumor DNA transfection and the augmentation of GD3 in malignant cells is discussed. Because of the early appearance of GD3 in hepatoma and its possible relationship to oncogene activation, GD3 may be a potentially useful early tumor marker.
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PMID:Enhanced expression of ganglioside GD3 in human and rat hepatocellular carcinoma cells and NIH 3T3 cells transfected with human tumor DNAs. 170 52

CMP-N-acetylneuraminic acid: glycoprotein sialyltransferase activities were assayed in microsomal fractions from chicken liver and hepatoma, induced by the leukosis virus strain Mc-29, using asialofetuin as the substrate acceptor of N-acetylneuraminic acid. The effect of some nucleotides and metal ions on the enzyme activity was investigated. Kinetic studies revealed that the Km values toward asialofetuin at a saturation concentrations of CMP-N-acetylneuraminic acid for both liver and hepatoma enzymes are very closed, while V value was lower for the tumor enzyme. The liver and hepatoma enzymes have no exogenous Mn cations requirement and are inhibited by CTP, CMP and ATP. CMP was shown to act as a competitive inhibitor with an apparent Ki of 0.24 mM for the liver and 0.16 mM for hepatoma enzyme, respectively.
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PMID:Partial characterization of microsomal sialyltransferase from chicken liver and hepatoma Mc-29: I. Effect of nucleotides and metal ions. 208 38

Microsomal sialyltransferase was assayed in chicken liver and hepatoma Mc-29 utilizing liver and hepatoma microsomal glycoprotein fractions, treated with Triton X-100, as exogenous acceptors. In a homologous assay system containing enzyme and acceptor from one and the same tissue no quantitative dependence of enzyme activity was revealed with increasing amount of the acceptor. In mixed experiments in which liver enzyme activity was tested towards hepatoma acceptor glycoproteins, a gradual drop in sialyltransferase activity occurred with increasing quantities of the acceptor. This effect seems to be a consequence of the presence of some inhibitor in the microsomal fractions from the hepatoma cells.
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PMID:Partial characterization of microsomal sialyltransferase from chicken liver and hepatoma Mc-29: II. Measurement of enzyme activities utilizing microsomal glycoproteins as exogenous acceptors. 208 39

1. Gal beta 1-4GlcNAc alpha 2-6 sialyltransferase was assayed in FAZA hepatoma cells and the cell culture medium following growth of cells in presence of dexamethasone and phorbol ester. 2. There was about a seven-fold increase in sialyltransferase activities in cells and medium in presence of dexamethasone with the maximum effect occurring at 10(-6)-10(-7) M dexamethasone. 3. The presence of 10(-6) M phorbol ester in the culture medium increased sialyltransferase activities in cells and medium by ca 40% over the values found with dexamethasone alone. 4. The use of the FAZA hepatoma cell line for studies on sialyltransferase is compared with the primary hepatocyte system reported on earlier (Woloski et al., 1986).
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PMID:Stimulation of release of Gal beta 1-4GlcNAc alpha 2-6 sialyltransferase from the FAZA hepatoma cell line by dexamethasone and phorbol ester. 218 55

Little is currently known about the mechanisms by which the cellular glycosylation machinery is regulated to produce cell type-specific glycosylation sequences on glycoprotein and glycolipid sugar chains. Previously, we have shown that one enzyme involved in terminal glycosylation, beta-galactoside alpha 2,6-sialyltransferase, is expressed in a tissue-specific fashion, with the highest enzyme activity as well as mRNA levels being found in the liver. In addition, the liver mRNA was found to be 4.3 kilobases (kb) in size as compared to a larger message of 4.7 kb in other tissues. To understand the cellular regulation of expression of this sialyltransferase, we have cloned the rat gene encoding the 4.3-kb liver mRNA and found that it spans 40 kb of genomic DNA and contains 6 exons. The gene was found to be very similar in size and exon organization to the murine beta 1,4-galactosyltransferase gene, even though this enzyme has no sequence homology to alpha 2,6-sialyltransferase. The promoter responsible for the production of the liver alpha 2,6-sialyltransferase mRNA is approximately 50-fold more active in a hepatoma cell line known to express this enzyme (HepG2) than in a cell line shown not to express this enzyme (Chinese hamster ovary) and contains consensus binding sites for the liver restricted transcription factors HNF-1 and DBP as well as the transcription factors AP-1 and AP-2. These observations are in accord with the restricted expression of the 4.3-kb mRNA, and provides evidence for the cellular regulation of glycosylation at the level of transcription.
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PMID:Organization of the beta-galactoside alpha 2,6-sialyltransferase gene. Evidence for the transcriptional regulation of terminal glycosylation. 224 92


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