Tunicamycin, inhibition

Tunicamycin Inhibits GIcNAc-P transferase, the enzyme catalyzing addition of GIcNAc to dolichol-P, the first step in the biosynthesis of oligosaccharide-P-P-dolichol... 

ST 13 fibroblasts maintained in a medium containing insulin differentiate into adipose-like cells. This conversion is characterized by the appearance of lipid droplets in the cytoplasm and by an increase in synthesis and accumulation of cellular triglyceride. The insulin binding increases about 10-fold during differentiation. Tunicamycin inhibits the differentiation and suppresses insulin-binding activity.551... 

Tunicamycin inhibits chemotactic aggregation when added during the first few hours of development [123-125]. Since these effects can be overcome by adding cAMP[123] it... 

J.S. Tkacz, O. Lampen, Tunicamycin inhibition of polyisoprenyl N-acetylglucosaminyl pyrophosphate... 

The first seven sugars are transferred to dolichol phosphate from nucleoside diphosphate sugars, UDP-N-acetylglucosamine and GDP-mannose. Each reaction is catalyzed by a separate glycosyltransferase. The antibiotic, tunicamycin, inhibits synthesis of all N-linked glycoproteins by inhibiting the first enzyme in the process. 

Lehle, L. Tanner, W. (1976) The Specific Site of Tunicamycin Inhibition in the Formation of Dolichol-bound -Acetylglucosamine Derivatives , FEBS Letters, 71,167-70 Lehle, L. Tanner, W. (1978) Biosynthesis and Characterization of Large Dolichol Diphosphate-linked Oligosaccharides in Saccharomyces cerevisiad, Biochimica et Biophysica Acta, 539, 218-29... 

Low levels (5 / g ml ) of the antibiotic tunicamycin inhibited the incorporation of 2-acetamido-2-deoxy-D-glucose into polyprenol sugars in cotton bolls and mung bean seedlings. Conversely, even high concentrations (500 ftg ml" ) of the antibiotic had no effect on the incorporation of D-mannose residues in similar tissue. 

The oligosaccharide GICjMangCGIcNAcjj is transferred from dolichol-P-P-oligosaccharide in a reaction catalyzed by oligosaccharide protein transferase, which is inhibited by tunicamycin. 

Secretion of nonglycosylated macromolecules in the presence of tunicamycin has also been investigated in a number of other cells. Rat-liver cell-secretion ol albumin (a carbohydrate-free protein), transferrin, and a-acid glycoprotein was not inhibited, and, in chick-liver cells, only a decrease by 10-25% in the secretion of transferrin and the apoprotein B chain of very-low-density lipoprotein was noted.463,464 The secretion of ovalbumin (a glycoprotein) from hen oviduct was not blocked by tunicamycin.465... 

Because concanavalin A also inhibited the conversion of procollagen into collagen by carboxyl-terminal protease, it was suggested that this protease contains oligosaccharide side-chains that are recognized by concanavalin A, and that tunicamycin affects the secretion, activity, or activation of this enzyme.484... 

Cell interactions leading to kidney-tubule determination are tunica-mycin-sensitive. When tunicamycin was applied at concentrations that prevent induction of differentiation, cells did not contain laminin, a glycoprotein that is detected in early stages of differentiation. As tunicamycin did not prevent differentiation when applied later during the morphogenetic period, the authors considered it unlikely that the drug interferes with tubule formation by inhibiting the secretion of laminin.493,494... 

Tunicamycin specifically inhibits cell division and pairing between the mating types of Tetrahymena pyriformis. The glycoproteins involved in this mating process have not yet been characterized, but may coincide with new, concanavalin A receptor-sites that appear during conjugation.495... 

Inhibition of glycosylation was shown to interfere with certain stages of development, as shown in the previous examples. However, in cultured, human and myeloid leukemia cells, tunicamycin treatment induced differentiation. From this observation, it has been concluded that glycosylation of cellular proteins plays a role in maintaining these cells in a transformed stated"... 

Tunicamycin and 2-deoxy-D-arahino-hexose interfere with the expression of lipase (glycerol-ester hydrolase, EC 3.1.1.3) in cultured, mesenchymal rat-heart cells. The causes of inhibition were not inves-... 

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