Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.4.99.7 (sialyltransferase)
 1,534 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Trout (Salmo gairdneri) serum is rich in glycoproteins which are synthetized in liver. 2. An attempt to localize glycosyltransferases in hepatocytes is described, using cellular fractionation and marker enzyme determination. 3. Galactosyltransferase, mannosyltransferase, N-acetyl-glucosaminyl transferase, glucosyltransferase, sialyltransferase (on exogenous acceptor) are found in a microsomal fraction obtained by centrifugation at 117 X 10(5) g min of the post-mitochondrial supernatant. 4. Mannose is transferred to endogenous lipids and proteins.
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PMID:Evidence for glycosyltransferases in trout liver microsomes (Salmo gairdneri). 31 19

The postnatal development of skeletal muscle is characterized by changes in membrane function associated with N-linked glycoproteins. In the present study, early reactions involved in the synthesis of the dolichol-linked core oligosaccharide were examined in neonatal and adult rabbit skeletal muscle sarcoplasmic reticulum membranes. The initial rate of N-acetylglucosamine incorporation in the presence of exogenous dolichol phosphate was similar between neonate and adult (3.5-4.1 pmol of GlcNAc/min/mg). The Km values for UDP-GlcNAc and exogenous dolichol phosphate were similar. Tunicamycin (0.04-0.08 micrograms/ml) inhibited N-acetylglucosamine incorporation by 50%. UDP-GlcNAc pyrophosphatase activity was greater in neonatal membranes than adult (840 versus 350 pmol of GlcNAc-1-P/min/mg), explaining, in part, the greater enhancement of neonatal GlcNAc incorporation by pyrophosphatase inhibitors. Nucleotide-sugar pyrophosphatase inhibitors (alpha, beta-methylene ATP and dimercaptopropanol) increased the capacity of neonatal activity 4-fold and adult enzyme 2-fold. Analysis of dolichol-linked products by mild acid hydrolysis however, revealed that neonate had higher capacity for N,N'-diacetylchitobiosyl(pyro)phosphoryldolichol synthesis than adult. Mannosyltransferase and glucosyltransferase were elevated 6- and 5-fold in neonate compared to adult membranes. Neonate exhibited 4-fold greater GDP-Man pyrophosphatase activity than adult (500 versus 125 pmol of Man-1-P/min/mg). The Km for GDP-Man increased in the presence of exogenous dolichol phosphate. Increasing concentrations of exogenous dolichol phosphate did not equalize neonate and adult mannosyltransferase activity, indicating that the decline in activity during development was not due to a decrease in a pool of dolichol phosphate accessible to mannosyltransferase. Glucosyltransferase for the synthesis of glucosylphosphoryldolichol was also elevated 5-fold in neonatal compared to adult sarcoplasmic reticulum (7 versus 1.4 pmol of Glc/min/mg). In a previous study, it was reported that glycoprotein sialyltransferase activity decreased by a factor of 6.5 during the postnatal maturation and that total membrane hexose content of sarcoplasmic reticulum decreased by a factor of 8. Together, these results suggest that the postnatal development of skeletal muscle is characterized by coordinated changes in the expression of enzymes involved in both the "early" and "late" reactions of N-linked oligosaccharide biosynthesis.
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PMID:Formation of dolichol-linked sugar intermediates during the postnatal development of skeletal muscle. 631 23

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.
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PMID:Impaired glycosylation in liver microsomes of orotic-acid-fed rats. 713 8

Definitive hematopoietic stem and progenitor cells (HSPCs) arise from the transdifferentiation of hemogenic endothelial cells (hemECs). The mechanisms of this endothelial-to-hematopoietic transition (EHT) are poorly understood. We show that microRNA-223 (miR-223)-mediated regulation of N-glycan biosynthesis in endothelial cells (ECs) regulates EHT. miR-223 is enriched in hemECs and in oligopotent nascent HSPCs. miR-223 restricts the EHT of lymphoid-myeloid lineages by suppressing the mannosyltransferase alg2 and sialyltransferase st3gal2, two enzymes involved in protein N-glycosylation. ECs that lack miR-223 showed a decrease of high mannose versus sialylated sugars on N-glycoproteins such as the metalloprotease Adam10. EC-specific expression of an N-glycan Adam10 mutant or of the N-glycoenzymes phenocopied miR-223 mutant defects. Thus, the N-glycome is an intrinsic regulator of EHT, serving as a key determinant of the hematopoietic fate.
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PMID:The N-glycome regulates the endothelial-to-hematopoietic transition. 3327 96