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Results for “Hexosyltransferases”

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At least 19 recordsLinked to original sources
PubMed1978

Evaluation of two plasma fucosyltransferases as marker enzymes in non-Hodgkin's lymphoma.

Levels of two fusosyltransferases were measured in plasmas of patients with non-Hodgkin's lymphoma at different phases of the disease. The level of a GDP-fucose: galactoside fucosyltransferase (EC 2.4.1.69) was found elevated in nonresponding patients and was correlated with estimated tumor burden. Enzyme levels in the normal range were found in patients in remission, maintained on chemotherapy, or unmaintained. The plasma level of a GDP-fucose; N-acetylglucosaminide fucosyltransferase (EC 2.4.1.68) was elevated in all individuals receiving drug therapy regardless of diesease status, but returned to normal levels during unmaintained remissions.

Acetylglucosamine↗
PubMed1975

Induction of hyaluronic acid synthetase activity in rat fibroblasts by medium change of confluent cultures.

Hyaluronic acid synthesis in cultured cells usually occurs during the growth phase. The relation between hyaluronic acid synthetase activity and cell proliferation is studied. The synthetase activity in rat fibroblasts is high during the growth phase, but low in the stationary phase. When the old medium of stationary cultures is renewed with fresh medium containing 20% calf serum, DNA synthesis occurs synchronously between 12 and 20 hours, followed by cell division. Under these conditions, the hyaluronic acid synthetase activity is significantly induced within two hours, reaching a maximum level at 5--8 hours, and then decreases gradually. This induction of the synthetase, which shows a high turnover rate, requires continued synthesis of both RNA and protein. Furthermore, the induction of both DNA and hyaluronic acid synthesis is found to be caused by calf serum added in the medium. However, dialysis and ultrafiltration of the serum permit us to concentrate an active fraction with a high molecular weight, which induces the synthetase activity, but not DNA synthesis.

Blood↗
PubMed1977

Glycosylation of VSV glycoprotein is similar in cystic fibrosis, heterozygous carrier, and normal human fibroblasts.

The single envelope glycoprotein of vesicular stomatitis virus was used as a specific probe of glycosyltransferase activities in fibroblasts from two cystic fibrosis patients, an obligate heterozygous carrier and a normal individual. Gel filtration of pronase-digested glycopeptides from both purified virions and infected cell-associated VSV glycoprotein which had been labeled with[3H] glucosamine did not reveal any significant differences in the glycosylation patterns between the different cell cultures. All 4 cell lines were apparently able to synthesize the mannose- and glucosamine- containing core structure and branch chains terminating in sialic acid which are characteristic of asparagine-linked carbohydrate side chains in cellular glycoproteins. Analysis of tryptic glycopeptides by anion-exchange chromotography indicated that the same 2 major sites on the virus polypeptide were recognized and glycosylated in all 4 VSV-infected cell cultures. These studies suggest that the basic biochemical defect(s) in cystic fibrosis is not an absence or deficiency in enzymes responsible for the biosynthesis of complex carbohydrate side chains.

Cell Line↗
PubMed1978

Cell surface glycosyltransferases--do they exist?

The presence of glycosyltransferases on surfaces of mammalian cells has been reported by many investigators and a biological role for these enzymes in cell adhesion and cell recognition has been postulated. Critical analysis, however, showed 2 major complications regarding the assay for cell surface glycosyltransferases: 1) hydrolysis of the nucleotide sugar by cell surface enzymes and subsequent intracellular use of the free sugar and 2) loss of cell integrity if trypsinized or EDTA-treated cells were used in suspension assays. We have assayed intact, viable cells in monolayer for cell surface glycosyltransferases using conditions under which intracellular utilization of free sugars generated by hydrolysis of the nucleotide sugar was prevented. Our data demonstrate that the presence of galactosyltransferases on the surface of a variety of cells, including established (normal and virally transformed) as well as nonestablished cells, is unlikely. No evidence for the existence of cell surface fucosyl- and sialytransferases could be obtained, but our data do not exclude the possibility that low levels of these enzymes are present.

Cell Line↗
PubMed1977

Glycoprotein alterations in human colonic adenocarcinoma.

A marked diminution in membrane glycoproteins containing blood group A activity was observed in colonic cancer tissues. This change was associated with a reduction of the enzyme responsible for its biosynthesis and a decreased concentration of N-acetylgalactosamine in the cancer tissues. Glycosidase activities were unchanged. In addition to the changes associated with blood group A, we also found a decrease in sugar content, alterations in other antigens, and changes in the levels of several glycosyltransferases in cancerous tissues.

Adenocarcinoma↗
PubMed1975

Relationship between microsomal hydroxylase and glucuronyltransferase.

These experiments did not answer the question of whether one or several UDG-glucuronyltransferases are present in endoplasmic membranes of the liver. However, they present results which indicate that the glucuronlytransferase (s) have several properties in common with the hydroxylating cytochrome P-450 dependent enzyme system: the inducibility (which differs considerably after pretreatment with phenobarbital or 3-methylcholanthrene), the sex specificity, and the inhibition by the same compounds. The most obvious difference between the systems is the alteration of the enzyme activities after solubilization of the membranes by sonication or use of detergents.. On solubilization, the activity of the glucuronyltransferase (s) increases, whereas the opposite is true for the hydroxylating system which may lose one or several components essential for its activity (such as the NADPH dependent reductase). Our experiments can best be interpreted by assuming a common micro-environment around the enzymes produced by lipids and proteins which modulate both the rate of hydroxylation and that of glucuronyl-conjugation of drugs.

Aminopyrine↗
PubMed1978

Antigens of Streptococcus mutans implicated in virulence--production of antibodies.

The present studies assayed antibody activities in serum and saliva of animals immunized by different routes, with cells of S. mutans or cell-free preparations containing GTF, FTF, LTA and/or dextranase synthesized by S. mutans. The results show that the type of immunogenic preparation and the route of its administration can elicit different antibody response and may in part explain the disparity of results achieved by different investigators. The results further emphasize the need to use standardized preparations and carefully described protocols for vaccination.

Animals↗
PubMed1978

Studies on secretory glycoproteins in the rat exocrine pancreas. II. Identification of a fetuin: fucosyl transferase in the smooth microsomal fraction.

A fetuin, fucosyl transferase has been identified in the smooth microsomal fraction from the rat exocrine pancreas. This enzyme is involved in the glycosylation of secretory proteins and is bound to membranes, predominantly of the Golgi complex. Optimal in vitro conditions for the assay of the enzyme activity were established: a pH of 5.5-6.0, a temperature of 21 degrees C and concentrations of Mg++ at 5.0 mM and ATP at 2.0 mM.

Adenosine Triphosphate↗
PubMed1977

Biosynthesis of the yeast cell wall: selective assays and regulation of some mannosyl transferase activities.

Assays have been developed for some transfer reactions involved in the synthesis of Saccharomyces cerevisiae wall mannoproteins, both in a particulate preparation in the presence of EDTA or Triton X-100, and after lipid extraction with chloroform-methanol at -20 C. The mannosyl transferase activities were also studied in cells made permeable to GDP-mannose by toluene-ethanol treatment ("in situ"). In these permeabilized cells, the glycosylating reactions dependent on lipid carriers (dolichol derivatives) did not function, but those independent of them were unaffected. The lipid-independent mannosyl transferase activities were partially inhibited by nucleotide diphosphates probably in a competitive manner. Increase of the nucleotide diphosphate pool "in vivo" might slow down the speed of the transfer reactions carried out by the mannan synthetase system.

Adenosine Diphosphate↗
PubMed1975

Estimation of hepatic bilirubin UDP-glucuronyl transferase in patients with noncirrhotic portal fibrosis and liver disease: Significance and limitations.

Using a micromethod, hepatic bilirubin UDP-glucuronyl transferase has been assayed in percutaneous needle biopsy samples obtained from patients with infectious hepatitis, postnecrotic cirrhosis, Gilbert's disease, noncirrhotic portal fibrosis (NCPF), granuloma of the liver, and extrahepatic portal vein obstruction. The results were compared with those obtained from 10 control subjects. Patients with cirrhosis and infectious hepatitis revealed normal bilirubin transferase levels, whereas those with Gilbert's disease showed significantly low enzyme levels. Many patients with NCPF, some with extrahepatic portal vein obstruction, and patients with granulomatous involvement of the liver demonstrated significantly low levels. This low hepatitic-enzyme activity was not associated with hyperbilirubinemia. The mechanism of such low values in NCPF and other disorders is not known. It is postulated that low heaptic-enzyme activity in noncirrhotic portal fibrosis is due to sparse smooth endoplasmic reticulum. This study also emphasizes that serum bilirubin may remain normal with very low hepatic-enzyme activity. Although induction of the microsomal enzyme bilirubin transferase was observed following phenobarbitone administration in noncirrhotic portal fibrosis, this was not apparent in patients with cirrhosis, possibly due to maximal enzyme induction having been achieved by endogenous substrate.

Adult↗
PubMed1976

Search for a biochemical basis of diabetic microangiopathy.

Diabetic microangiopathy, particularly as seen in the renal glomerulus, is characterized by morphological and biochemical alterations of the capillary basement membrane. Observations from a number of disciplines have indicated that the microvascular disease is not a separately inherited entity but a true consequence or "complication" of insulin deficiency. An evaluation of the biochemical events which could be responsible for the basement membrane lesions of diabetes indicates that the hyperglycemia or plasma somatotropin elevation of this disease alone, or in combination, may play an important role.

Animals↗