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)

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

L-Fucose and N-acetylneuraminic (sialic) acid occupy terminal positions on the oligosaccharide side-chains of human cervical mucin but the addition of both these monosaccharides to the same carbohydrate acceptor residue is kinetically unfavourable. The following evidence suggests that the levels of L-fucose are more sensitive to regulation than those of N-acetylneuraminic acid: (1) tissue levels of sialyltransferase (EC 2.4.99.1) activity are 20-30 times greater than those of fucosyltransferase (EC 2.4.1.68); (2) both glycosyltransferases are susceptible to inhibition by their nucleotide products but a comparison of the Ki and the apparent Km of these enzymes shows that modulation of fucosyltransferase is more probable; (3) Postsecretory removal of L-fucose from cervical mucin is probably due to the high levels of mucus-associated alpha-L-fucosidase. Furthermore the activity of this enzyme is probably modulated by the pH gradient within the cervix. Mucin glycosylation can be visualized by autoradiography using [3H]L-fucose applied to cervical explants in organ culture. Mucus production during this process is not sensitive to exogenous ovarian steroid hormones, though in other aspects the secretory process appears normal. It is proposed that the cyclicity of mucus rheology is not directly influenced by an action of these hormones on mucin synthesis or hydration.
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PMID:Terminal glycosylation in human cervical mucin. 656 36

Mammalian spermatozoa must undergo maturational changes between the events of mating and fertilization. These biochemical and functional alterations, collectively termed capacitation, take place as spermatozoa traverse the female reproductive tract. The preparatory biochemical changes include removal, modification, and reorganization of sperm surface molecules. Although details of all the changes are not known, lectin binding studies have provided evidence suggesting that carbohydrate moieties of sperm surface glycoproteins are modified during capacitation. In an attempt to gain insight into the potential modifications of sperm plasma membrane glycoproteins, we quantified glycoprotein-modifying enzyme activities in the uterine and oviductal fluid of the hamster during the 4 days of the estrous cycle. These enzymes are known to modify existing glycoproteins, either by adding sugar residues (glycosyltransferases) or by removing terminal sugar residues (glycosidases). Data from these studies showed that 1) levels of all glycosyltransferase activities assayed (sialyltransferase, fucosyltransferase, galactosyltransferase, and N-acetylglucosaminyltransferase) were negligible in the uterine fluid at the onset of ovulation (Day 1) but sharply increased preceding ovulation (Day 4); 2) levels of the four glycosyltransferase activities assayed were higher in the oviductal fluid at the onset of ovulation (Day 1) and then gradually decreased through the remainder of the estrous cycle (Day 2 to Day 4); 3) levels of all glycohydrolase activities (acidic alpha-D-mannosidase, beta-D-galactosidase, beta-D-glucuronidase, beta-D-glucosaminidase, and alpha-L-fucosidase) and protein in the uterine and oviductal fluids did not vary widely during the 4 days of the cycle. These results demonstrate a temporal surge of glycosyltransferase activities in the genital tract fluids of the hamster. The temporal changes in the glycoprotein-modifying enzymes may have an effect on the glycosylation of sperm plasma membrane and zona pellucida glycoproteins at the site of fertilization or may alter the surface glycoproteins of the fertilized egg in the uterus prior to implantation.
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PMID:Temporal surge of glycosyltransferase activities in the genital tract of the hamster during the estrous cycle. 872 23

The aim of this study was to determine the role of polyamines in the diet-related maturation of the intestinal glycoprotein glycosylation during postnatal development in the rat. The activity of alpha-2,6-sialyltransferase and the sialylated forms of glycoproteins in the intestinal brush-border membranes were found to decrease considerably after weaning, in parallel with the intestinal level of putrescine. By contrast, the activity of alpha-1,2-fucosyltransferases, the mRNA levels for two alpha-1,2-fucosyltransferase genes, FTA and FTB, and the fucosylated forms of glycoproteins all increased after weaning, in parallel with the levels of spermidine and spermine. These results suggest a possible role of polyamines in the evolution of glycosylation. The treatment of suckling rats with spermidine or spermine reproduced the high intestinal levels of these polyamines corresponding to those normally found after weaning. After these treatments, a rise in the activity of the alpha-1,2-fucosyltransferase was observed, associated with a fall in alpha-L-fucosidase activity. The alpha-1,2-fucosyltransferase FTB gene was found to be regulated at the transcriptional level, but not by its inhibitor, fuctinin. The result of these variations was the precocious appearance of several alpha-1,2-fucoproteins, which are normally found in brush-border membranes after weaning. The treatment of suckling rats with putrescine, which induced only a transitory rise in intestinal putrescine, had a similar but weaker effect on the fucosylation process than spermidine or spermine, and treatment with ornithine was ineffective. alpha-2,6-Sialylation was not affected by any of the treatments. Spermidine and spermine turned out to be more effective than putrescine for intestinal glycoprotein fucosylation, but did not affect their sialylation. Spermidine and spermine, whose intestinal levels where found to increase at weaning time, may have been partly responsible for the natural evolution of the intestinal glycoprotein fucosylation that occurred during this period.
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PMID:Polyamine participation in the maturation of glycoprotein fucosylation, but not sialylation, in rat small intestine. 1197 88