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)

Optimal assay conditions were determined for four glycosyltransferases in rat small intestinal mucosal homogenates and the regional distribution and cellular localization of these enzymes was studied. For each glycosyltransferase, similar levels of activity were found in duodenal, proximal jejunal and distal ileal segments; activities of the galactosyltransferases were lower in the distal jejunal-proximal ileal segment. Planar section studies indicated that the undifferentiated crypt cells had significantly higher levels of sialyltransferase activities in the jejunum and ileum than the mature villus cells. A similar crypt to villus gradient was found for a galactosyltransferase in the ileum. These data suggest that glycoprotein synthesis may be active in the undifferentiated crypt cells and that certain glycosyltransferases may serve as marker enzymes for cellular differentiation in the intestine.
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PMID:Regional and cellular localization of glycosyltransferases in rat small intestine. Changes in enzymes with differentiation of intestinal epithelial cells. 4 96

Sialyltransferase(s) activity [CMP-N-acetylneuraminic acid:glycoprotein sialyltransferase(s) E.C. 2.4.99.1] was assayed using asialofetuin as a substrate in a total microsomal fraction obtained from rat liver. Rats pretreated with phenobarbital or methylcholanthrene demonstrated a decrease in membrane bound sialyltransferase(s) activity of 27% and 18%,respectively. Microsomes prepared from phenobarbital treated rats were incubated in vitro with aflatoxins B1, B2, B2a, G1, or G2 in the presence or absence of an NADPH generating system. Following this treatment the microsomes were reisolated, washed and assayed for sialyltransferase(s) activity. Aflatoxin B1 and B2a inhibited sialyltransferase(s) by 46% and 55%, respectively, while aflatoxin G1 inhibited sialyltransferase(s) by 54%. Aflatoxins B2 and G2 were only slightly inhibitory. It is proposed that the enzyme inhibition caused by these various aflatoxins is due to binding of these agents to the membranes resulting in a local disruption of the membrane and a change in enzyme conformation.
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PMID:Differential inhibition of rat liver sialyltransferase(s) by various aflatoxins and their metabolites. 5 Jun 14

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

When compared to uninvolved adjacent tissue, metastatic tumors in human liver appear to have significantly reduced sialytransferase activity. No significant kinetic differences (Michaelis constants, thermostability, and pH optima) between noncancerous and cancerous tissue sialytransferase were found. Mixing experiments between cancerous and noncancerous tissues indicated that inhibitors of sialytransferase activity were present in cancerous tissue. Subsequent experiments demonstrated increased levels of bound sialic acid in the tumor tissues. Inasmuch as futuin, a sialoglycoprotein, inhibits sialyltransferase activity, the increased levels of bound sialic acid in tumor tissue may be responsible for the reduced enzyme activity in these tissues.
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PMID:Characterization of sialytransferase in noncancerous and neoplastic human liver tissue. 8 33

We synthesized on Tn erythrocytes with human sera, UDP-Gal, and activators T-specific haptenic structures in satisfactory yield. The specificity of this biosynthesis was ascertained by agglutination with human and animal anti-T, by specific absorption of human anti-T as well as by agglutination inhibition assays. With isolated human erythrocyte T antigen as substrate we synthesized N- and M-specific structures with sera from individual human donors in presence of CMP-sialic acid by incubation for 24 hr at 37 degrees C. Serology on the recovered product was carried out with nineteen monospecific human and animal sera under strictly standardized and controlled conditions with the mandatory tube assay. All M- as well as N-derived T antigens tested acquired N specificity with all transferase sera of all MN types. In contrast, M-activation of M- and N-drived T antigens tested acquired N specificity with all transferase sera of all MN types. In contrast, M-activation of M- and N-derived T antigens occurred only if the transferase donor had the M gene. The nine M transferase sera used all gave M-activation of MM- and NN-derived T antigens. None of twelve transferase sera from NN donors M-activated any T antigen. NN antigen was transformed to a M-specific one by all transferase sera from MM donors but by none from NN donors. We have not yet established the biochemical-genetic relation of M to N; N may be the immediate precursor of M or M may originate directly from T. The sialyltransferase responsible for M activation may be a N transferase 'modified' by the M gene product or an entirely different sialyltransferase.
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PMID:Biosynthesis of human blood group T-, N- and M-specific immunodeterminants on human erythrocyte antigens. 9 34

Human factor VIII/von Willebrand factor protein containing 120 +/- 12 nmol of sialic acid and 135 +/- 13 nmol of galactose/mg of protein was digested with neuraminidase. The affinity of native factor VIII/von Willebrand factor and its asialo form for the hepatic lectin that specifically binds asialoglycoproteins was assessed from in vitro binding experiments. Native factor VIII/von Willebrand factor exhibited negligible affinity while binding of the asialo derivative was comparable to that observed for asialo-alpha1-acid glycoprotein. Incubation of asialo-factor VIII/von Willebrand factor with Streptococcus pneumoniae beta-galactosidase removed only 62% of the galactose but abolished binding to the purified hepatic lectin. When the asialo derivative was incubated with purified beta-D-galactoside alpha2 leads to 6 sialyltransferase and CMP-[14C]NeuAc, only 61% of the galactose incorporated [14C]NeuAc. From the known specificites of these enzymes, it is concluded that galactose residues important in lectin binding are present in a terminal Gal/beta1 leads to 4GlcNAc sequence on asialo-factor VIII/von Willebrand factor. The relative ristocetin-induced platelet aggregating activity of native, asialo-, and agalacto-factor VIII/von Willebrand factor was 100:38:12, respectively, while procoagulant activity was 100:100:103.
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PMID:Carbohydrate on human factor VIII/von Willebrand factor. Impairment of function by removal of specific galactose residues. 10 Apr 92

As the initial step toward the cytochemical localization of glycosyl-transferases in situ, biochemical determinations of these enzyme activities from onion root tips and L1210 cells were performed before and after fixation as well as in the presence of lead ions. Glycosyltransferase activity from roots fixed in buffered formaldehyde or glutaraldehyde before homogenization decreased as the concentration of the fixative or fixation time was increased. Formaldehyde fixation was less inhibitory than glutaraldehyde; 35% of the glycosyltransferase activity was retained after 30 min fixation in 2% formaldehyde while 25% of the enzyme activity remained after a similar fixation in glutaraldehyde. Substantially higher levels of L1210 cell glycosyltransferase activity were retained after a 30 min 2% formaldehyde fixation (60% sialyltransferase; 82% galactosyltransferase), but inhibition by glutaraldehyde was similar to that observed for onion root galactosyltransferase. Glycosyltransferase from formaldehyde-fixed roots was inhbited 35% by lead nitrate, but sialytransferase from formaldehyde-fixed L1210 cells was unaffected by lead ions. These findings are encouraging for further studies aimed at the development of cytochemical technique to localize glycosyltransferase in plant and animal tissues.
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PMID:Glycosyltransferases in plant and animal tissues effects of fixation and lead on enzyme activity. 10 86

The morphological changes induced by butyrate in HeLa cells and by monobutyryl or dibutyryl cAMP in CHO cells are prevented by micromolar concentrations of the divalent cation ionophore A23187. The ionophore is unable to prevent such changes in medium from which calcium is omitted. At slightly higher (but nontoxic) concentrations, the ionophore inhibits the butyrate-mediated induction of the ganglioside biosynthetic enzyme, sialyltransferase, in HeLa. In CHO, sialyltransferase activity is normally high and not altered by any of the compounds tested.
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PMID:Morphological changes in cultured mammalian cells: prevention by the calcium ionophore A23187. 16 98

Mouse cells transformed by a temperature-sensitive mutant of simian virus 40 belonging to complementation group A lost their ability to regulate cell growth when grown at the permissive temperature (35 degrees) but showed the low saturation density of cell growth at the restrictive temperature (39.5 degrees) that is characteristic of normal cells in vitro. Biochemical analysis of the membranes of cells grown under the restrictive and the permissive conditions demonstrated no qualitative temperature-dependent differences either in neutral glycolipids or in acidic glycolipids of the cells. Plasma membrane glycoproteins labeled with radioactive glucosamine showed significantly different patterns on both polyacrylamide gel electrophoresis and electrofocusing. When the levels of glycoprotein glycosyltransferases of the cells were examined, the level of sialyltransferase (CMP-N-acetylneuraminytransferase,EC 2.4.99.1) of the cells grown at the restrictive temperature was low compared with that of cells grown at the permissive temperature. Our results indicate that the level of sialyltransferase is under the control of the gene A function of simian virus 40 and consequently is related to alterations in the cell surface glycoproteins.
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PMID:Alterations in surface glycoproteins and level of sialyltransferase of cells transformed by a temperature-sensitive mutant of simian virus 40. 18 85

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


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