Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.4.99.10 (sialyltransferase)
 1,547 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Studies on developmental changes of ganglioside synthesis and compositions were carried out using rat bone marrow cells, spleen and thymus. Ganglioside synthesis was studied by assaying sialyltransferase for GM3 synthesis and GM1b synthesis. In bone marrow cells, peaks of both enzyme activities occurred coincidentally in 2- to 5-week-old rats. In spleen, the highest activities of these enzymes were observed in one-week-old rats. GM1b synthesis in the thymus was almost constant after birth, but GM3 synthesis could not be detected at any age examined. Developmental changes of gangliosides in these tissues were analyzed by thin layer chromatography. Gangliosides corresponding to GM1b and GM3 were recognized in each tissue. The ganglioside content of the bone marrow cells increased in 2- to 5-week-old rats. Ganglioside corresponding to GM1b was isolated from the bone marrow cells, and its structure was confirmed to be the same as that of GM1b by sequential hydrolysis of the ganglioside with glycosidases. GM3 was a predominant ganglioside in newborn rat spleen. Ganglioside content in the spleen increased during 2-5 weeks after birth and became constant after 9 weeks. In the thymus, more than 10 different gangliosides were discriminated, but significant changes of ganglioside pattern with the progress of development could not be observed. The developmental change of the ganglioside composition coincided well with the change of sialyltransferase activities.
J Biochem 1983 Sep
PMID:Developmental changes of ganglioside compositions and biosyntheses in rat bone marrow cells, spleen and thymus. 664 28

We isolated the Golgi-rich fraction from rat ascites hepatoma AH-130 cells and rat liver, and compared some properties of glycosyltransferases using various acceptors. The specific activity of sialyltransferase in the hepatoma Golgi fractions was reduced to 19--41% depending upon the acceptor used (asialo-orosomucoid, asialo-fetuin or asialo-mucin), as compared to that of the normal liver Golgi fraction. However, no significant difference between the enzymes from the two sources was observed in pH optimum, requirements for the enzyme activity, and Km values for the donor substrate (CMP-sialic acid) and various acceptors used. The specific activity and other kinetic parameters of hepatoma galactosyltransferase were not significantly different from those of the liver enzyme, when assayed with N-acetylglucosamine, asialo-agalacto-fetuin and asialomucin as acceptors. Glycosyltransferases in the hepatoma and liver Golgi fractions were then assayed with plasma membranes from both sources as exogenous acceptor. Hepatoma sialyltransferase activity was much lower (1/2 to 1/4) than that of the normal liver. Galactosyltransferase activity, however, was found to be slightly higher in the hepatoma Golgi fraction than in the normal liver. Acceptor plasma membranes which were thus glycosylated in vitro by each Golgi enzyme were separated into protein and lipid fractions, and the latter fraction was further analyzed by thin layer chromatography. The results suggest that the hepatoma Golgi had much lower levels of glycoprotein : sialyltransferase and asialo-GM1 : sialyltransferase, but had an increased activity of asialo-GM3 : sialyltransferase. It is also suggested that the hepatoma Golgi had a high activity for the formation of di- and tri-glycosylceramides, for which the liver Golgi showed negligible activity.
J Biochem 1982 Sep
PMID:Characterization of glycosyltransferases in the Golgi complex from rat ascites hepatoma AH-130 cells: a comparison with those from normal liver. 681 67

In rats fed orotic acid, the incorporation in liver subcellular fractions of sugars injected intraperitonealy is altered only for mannose, but not for fucose or galactose. Direct determinations of several glycosyltransferases are done in smooth and rough microsomes: fucosyl-, glactosyl-, N-acetylglucosaminyltransferase activities are at quite similar levels in normal and fatty livers. By contrast, sialyltransferase activity is increased (+50%) in smooth microsomes of fatty livers, while mannosyltransferase activity is inhibited by 30%. These alterations are not caused by interfering reactions (pyrophosphatases or proteases). For the mannosyltransferase activity, the inhibition is found in the dolichylphosphorylmannose intermediates. Kinetic studies suggest that there is deficiency of both enzyme and endogenous dolichyl phosphate.
Biochim Biophys Acta 1982 Sep 17
PMID:Impaired glycosylation in liver microsomes of orotic-acid-fed rats. 713 8

Sialic acid metabolism was investigated in control rat liver, in regenerating liver at 24 h and 48 h after partial hepatectomy and in the liver of sham-operated animals. High levels of membrane-bound neuraminidase, with no detectable changes in the soluble enzyme, were observed in regenerating rat liver. The neuraminidase activities in the liver of sham-operated rats were identical to those present in control liver. High levels of CMP-N-acetylneuraminic acid synthetase and sialyltransferase were observed both in regenerating liver as well as in the liver of sham-operated rats. The sialic acid content of regenerating rat liver, which was lower than that found in the liver of control and sham-operated rats at 24 h, returned to normal values 48 h after surgery.
Cancer Lett 1981 Sep
PMID:Sialic acid metabolism in regenerating rat liver. 730 57

The observation that the activity of sialyltransferase (EC 2.4.99.1; serum glycoprotein:N-acetylneuraminic acid transferase) is often elevated in the serum of cancer patients necessitates an elucidation of the interrelationships of this serum enzyme with host tissues. Accordingly, the activity of this enzyme in serum, tumor, and liver was determined at various times after implantation of the R3230AC mammary carcinoma into Fischer rats. Results from samples obtained at numerous, sequential time points demonstrated that significant elevations in serum sialyltransferase enzyme activity occurred only in animals bearing large tumor burdens, i.e., greater than 20 g, or in animals with tumors present for longer than 21 days. In these tumor-bearing rats, the activity of sialyltransferase increased in liver tissue at 21 to 25 days concurrently with the increase in serum enzyme activity, suggesting that the liver may be a potential source of the serum enzyme. Sialyltransferase activity in tumor tissue was quite variable; the activity increased one week after tumor implantation and remained at the same level thereafter. When tumors were excised, the activity of the serum enzyme returned to control values within four days after surgery, suggesting that the half-life of serum sialyltransferase was two days. Serum enzyme levels were again elevated upon regrowth of the tumor. These results show that the serum sialyltransferase alters its activity in conjunction with changes in tumor burden.
Cancer Res 1980 Sep
PMID:Correlation of serum, tumor, and liver serum glycoprotein: N-acetylneuraminic acid transferase activity with growth of the R3230AC mammary tumor in rats and relationship of the serum activity to tumor burden. 742 28

Three melanomas of C57BL/6 mice (BL6, JB/MS, and JB/RH) share several phenotypic properties. All these cells contain melanoma-specific ecotropic C-type retrovirus that encodes melanoma-associated antigen recognizable by MM2-9B6 mAb. They do not express H-2Kb molecules, and the alpha-galactosyl epitopes (Gal alpha 1-3Gal beta 1-4GlcNAc-R) they fail to react with soybean agglutinin (SBA), peanut agglutinin (PNA), and vicia villosa (VV) lectins. Previously, we found that failure of BL6 melanoma cells to express alpha-galactosyl epitopes is due to down-regulation of alpha 1,3 galactosyltransferase (alpha 1,3GT) gene expression. To evaluate the possible role of alpha-galactosyl cell membrane carbohydrates in regulation of metastatic properties, individual clones isolated from BL6, JB/MS, and JB/RH melanomas were transfected with alpha 1,3GT cDNA. This resulted in appearance of alpha-galactosyl epitopes, as well as of carbohydrates reacting with SBA, PNA, or VV lectins, but did not affect expression of H-2 class I molecules or melanoma-associated antigen. Appearance of SBA, PNA, and VV lectin binding carbohydrates in the alpha 1,3GT gene-transfected melanoma cells is a result of reduction of cell membrane sialylation and unmasking of these carbohydrates. Reduction in cell membrane sialylation in the alpha 1,3GT gene-transfected melanoma cells is probably due to the competition between alpha 1,3GT with alpha 2,3 sialyltransferase or alha 2,6 sialyltransferase for the common acceptor N-acetyllactosamine in the Golgi apparatus. As a result of this competition, cell membranes of alpha 1,3GT gene-transfected melanoma cells became galactosylated and less sialylated. In parallel with alteration of cell membrane carbohydrates, transfection of the alpha 1,3GT gene leads to the loss of metastatic properties of the transfected melanoma cells in the immunocompetent and immunosuppressed C57BL/6 mice. Thus, the use of specific glycosyltransferase cDNA transfection presents direct experimental confirmation of the importance of cell membrane carbohydrates in the regulation of metastatic properties of tumor cells.
Cancer Res 1995 Sep 15
PMID:Alterations of cell surface carbohydrates and inhibition of metastatic property of murine melanomas by alpha 1,3 galactosyltransferase gene transfection. 754 89

Polysialic acid, or PSA, is a term used to refer to linear homopolymers of alpha(2,8)-sialic acid residues displayed at the surface of some mammalian cells. PSA is typically linked to the neural cell adhesion molecule N-CAM, where it can modulate the homotypic adhesive properties of this polypeptide. PSA expression is developmentally regulated, presumably through mechanisms involving regulated expression of sialyltransferases involved in PSA biosynthesis. Several different sialytransferase sequences have been implicated in PSA expression, although the precise roles of these enzymes in this context remain unclear. One such sequence, termed STX, maintains approximately 59% amino acid sequence identity with another sialyltransferase (PST-1, from hamster; PST, human) that is known to participate in PSA expression. While a murine STX fusion protein can catalyze the synthesis of a single alpha(2,8)-sialic acid linkage in vitro, the ability of STX to participate in PSA expression in vivo has not been demonstrated. We show here that STX transcripts are present in a PSA-positive, N-CAM-positive human small cell carcinoma line (NCI-H69/F3), but are absent in a variant of this line (NCI-H69/E2) selected to be PSA-negative and N-CAM-positive. To functionally confirm this correlation, we have cloned a human cDNA encoding the human STX sequence, and show, by transfection studies, that human STX can restore PSA expression when expressed in the PSA-negative, N-CAM-positive small cell carcinoma variant. We furthermore show that STX can confer PSA expression when expressed in a PSA-negative, N-CAM-positive murine cell line (NIH-3T3 cells), or when expressed in PSA-negative, N-CAM-negative COS-7 cells. These observations imply that STX, like PST-1/PST, can determine PSA expression in vivo. When considered together with the correlation between STX expression and PSA expression in vivo in the brain, these results suggest a regulatory role for STX in PSA expression in the developing central nervous system and small cell lung carcinoma.
J Biol Chem 1995 Sep 29
PMID:A human STX cDNA confers polysialic acid expression in mammalian cells. 755 89

Sialyl-Lewisx (NeuAc alpha 2-->3Gal beta 1-->4[Fuc alpha 1-->3]GlcNAc] has been identified as a ligand for E-selectin, P-selectin and recently also for L-selectin. We have synthesized the sialyl-Lewisx tetrasaccharide by total enzymatic synthesis from N-acetyllactosamine using a placental alpha 2-->3-sialyltransferase specific for type-2 chain acceptors, followed by a cloned human alpha 1-->3-fucosyltransferase (FucTV, the 'plasma-type' enzyme). This procedure resulted in the tetrasaccharide in a 61% overall yield.
FEBS Lett 1993 Sep 20
PMID:Efficient enzymatic synthesis of the sialyl-Lewisx tetrasaccharide. A ligand for selectin-type adhesion molecules. 769 Jul 13

A new class of gangliosides, GT1a alpha and GQ1b alpha, were initially identified as cholinergic neuron-specific antigens in bovine brain. These gangliosides have in common alpha 2-6 NeuAc linked to the GalNAc residue in the gangliotetraose core structure. In this study, we have determined the biosynthetic pathways of GT1a alpha and GQ1b alpha using rat liver Golgi fraction. The results showed that GT1a alpha and GQ1b alpha were synthesized from GD1a and GT1b, respectively, by the action of a GalNAc alpha 2-6 sialyltransferase. It was also demonstrated that these two gangliosides were found to exist as extremely minor components in rat liver.
FEBS Lett 1994 Sep 05
PMID:Biosynthetic pathway for a new series of gangliosides, GT1a alpha and GQ1b alpha. 808 83

A striking biochemical alteration to the epithelium of the small intestine upon weaning is the loss of microvillar sialic acids. Antibody and cDNA probes to the beta-galactoside alpha 2,6-sialyltransferase (SiaT-1, EC 2.4.99.1) were used to characterize the expression of this sialyltransferase in the small intestine of suckling rats. SiaT-1 mRNA and protein in the intestinal epithelium are rapidly lost upon weaning, in agreement with the loss of mucosal sialic acids and general sialyltransferase activity. Developmental repression of SiaT-1 is manifested in a proximal to distal gradient; SiaT-1 mRNA and protein are lost first from the duodenum and persist the longest in the ileum. We have previously documented that SiaT-1 gene expression can be transcriptionally initiated from a number of distinct tissue-specific promoter regions. Here, by criteria of mRNA mobility on agarose gels, primer extension analysis, and differential Northern hybridization, we show that the promoter previously considered to be liver-specific is operative in SiaT-1 expression in the small intestine of suckling animals. Comparison of this SiaT-1 promoter region with promoter regions of other genes exhibiting dual intestine-hepatic tissue specificity revealed a number of striking sequence similarities. Regulatory implications and consequences of small intestinal SiaT-1 expression in suckling but not in weaned animals are discussed.
Dev Biol 1994 Sep
PMID:Developmental regulation of beta-galactoside alpha 2,6-sialyltransferase in small intestine epithelium. 808 31


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