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)

We have recently demonstrated the presence of sialyltransferase and sialic acid in a trans-tubular network (TTN) continuous with trans Golgi apparatus cisternae of rat liver hepatocytes. Based on these findings, we concluded that this structure, which also exhibited thiamine pyrophosphatase and acid phosphatase activity, is an integral part of the Golgi apparatus and functions in sialylation. In the present study, by comparing the distribution of a major hepatocyte secretory product with that of sialyltransferase, we sought to determine whether the TTN is also part of the secretory pathway. Examination of adjacent serial thin sections labeled for albumin showed its presence throughout the TTN and simultaneously provided new details about the structural complexity of the TTN. Double-immunolabeling with protein A-gold allowed the direct demonstration of albumin throughout the sialyltransferase containing TTN. Additional double staining protocols (combination of preembedding enzyme cytochemistry with postembedding immunolabeling) revealed the presence of albumin in both the thiamine pyrophosphatase and acid phosphatase positive regions of the TTN. These data show that albumin, a nonglycosylated secretory protein, reaches the TTN where terminal glycosylation of glycoproteins occurs. Therefore, it appears that the TTN of rat hepatocytes which functions in terminal glycosylation is also part of the constitutive secretory pathway.
 ...
PMID:The trans-tubular network of the hepatocyte Golgi apparatus is part of the secretory pathway. 302 5

Interactions between selectins and their oligosaccharide-decorated ligands play a crucial role in the initiation of leukocyte extravasation. We have shown that synthetic multivalent sialyl Lewis x glycans inhibit strongly the adhesion of lymphocytes to endothelium at sites of inflammation. However, enzyme-assisted synthesis of these oligosaccharides si hampered by the lack of sufficient amounts of specific glycosyltransferases. We report here the construction of Saccharomyces cerevisiae strains expressing the soluble catalytic ectodomain of rat Gal(beta)1-3/4GlcNac alpha 2,3-sialyltransferase (ST3Ne) fused to the C-terminus of the hsp150 delta-carrier polypeptide. The hsp150 delta-carrier, which is an N-terminal fragmented of a natural secretory protein of yeast, is able to confer secretion-competence to several heterologous proteins, which otherwise remain in the yeast endoplasmic reticulum. The ST3Ne portion of the hsp 150 delta-ST3Ne fusion protein adopted an enzymatically active conformation and was N-glycosylated and disulfide-bonded. Hsp150 delta-ST3Ne was secreted with a half-time of about 7.5 min and remained intercalated in the cell wall, which covers the yeast plasma membrane. About 110 mU of sialyltransferase per litre was produced in 16 h. Whole live yeast cells were able to transfer sialic acid from CMP-NeuNAc to N-acetyllactosamine yielding alpha 2,3-sialyl-N-acetyllactosamine, as evidenced by paper chromatography, cleavage by linkage-specific sialidase, and NMR analysis. Our data suggest that yeast cells externalizing mammalian glycosyltransferases with the aid of the hsp150 delta-carrier could provide a source of enzymes for synthesis of valuable oligosaccharides.
 ...
PMID:Targeting of active rat alpha 2,3-sialyltransferase to the yeast cell wall by the aid of the hsp 150 delta-carrier: toward synthesis of sLe(x)-decorated L-selectin ligands. 902 48