Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.4.99.6 (sialyltransferase)
 1,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Membranes from chick embryo epiphyseal cartilage were fractionated by equilibrium sucrose density gradient centrifugation and assayed for galactosyl xylose transferase, chondroitin polymerization and sulfation as well as the marker enzymes glucose-6-phosphatase, NADH cytochrome c reductase, galactosyl ovalbumin transferase, and sialyltransferase. The order of distribution of chondroitin sulfate synthesis from dense to light membranes correlated with the established sequence of events for its synthesis. The linkage region enzyme, viz. galactosyl xylose transferase, distributed with NADH cytochrome c reductase in an earlier and heavier cis compartment. Chondroitin polymerization and sulfation had a dual distribution similar to the galactosyl ovalbumin transferase and sialyltransferase in separate later and lighter medial and trans compartments, or in an extended medial or trans compartment. The galactosyl xylose transferase had a distribution distinctly different from that of the galactosyl ovalbumin transferase indicating that these distinct enzymes showed no cross-reactivity with their respective acceptor substrates. The dual distribution of chondroitin sulfate synthesis was consistent with our previous demonstration of the two nascent proteochondroitin populations produced by microsomal preparations from the same source. The results indicated separate subcellular locations for synthesis of the two forms.
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PMID:Subfractionation of chick embryo epiphyseal cartilage Golgi. Localization of enzymes involved in the synthesis of the polysaccharide portion of proteochondroitin sulfate. 185 50

Nucleotide pyrophosphatase/phosphodiesterases (NPPs) are widely distributed N-glycosylated enzymes that catalyze the hydrolytic breakdown of numerous nucleotides and nucleotide sugars. In many plant species, NPPs are encoded by a small multigene family, which in rice are referred to NPP1-NPP6 Although recent investigations showed that N-glycosylated NPP1 is transported from the endoplasmic reticulum (ER)-Golgi system to the chloroplast through the secretory pathway in rice cells, information on N-glycan composition and subcellular localization of other NPPs is still lacking. Computer-assisted analyses of the amino acid sequences deduced from different Oryza sativa NPP-encoding cDNAs predicted all NPPs to be secretory glycoproteins. Confocal fluorescence microscopy observation of cells expressing NPP2 and NPP6 fused with green fluorescent protein (GFP) revealed that NPP2 and NPP6 are plastidial proteins. Plastid targeting of NPP2-GFP and NPP6-GFP was prevented by brefeldin A and by the expression of ARF1(Q71L), a dominant negative mutant of ADP-ribosylation factor 1 that arrests the ER to Golgi traffic, indicating that NPP2 and NPP6 are transported from the ER-Golgi to the plastidial compartment. Confocal laser scanning microscopy and high-pressure frozen/freeze-substituted electron microscopy analyses of transgenic rice cells ectopically expressing the trans-Golgi marker sialyltransferase fused with GFP showed the occurrence of contact of Golgi-derived membrane vesicles with cargo and subsequent absorption into plastids. Sensitive and high-throughput glycoblotting/mass spectrometric analyses showed that complex-type and paucimannosidic-type glycans with fucose and xylose residues occupy approximately 80% of total glycans of NPP1, NPP2 and NPP6. The overall data strongly indicate that the trans-Golgi compartments participate in the Golgi to plastid trafficking and targeting mechanism of NPPs.
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PMID:N-Glycomic and Microscopic Subcellular Localization Analyses of NPP1, 2 and 6 Strongly Indicate that trans-Golgi Compartments Participate in the Golgi to Plastid Traffic of Nucleotide Pyrophosphatase/Phosphodiesterases in Rice. 2733 51