It is recommended that the enzyme described here be designated CMP-NeuNAc:poly-α-2,8-sialosyl sialyltransferase and the trivial name poly-α-2,8-sialosyl sialyltransferase be adopted.Ībstract = "Prokaryotic derived probes that specifically recognize α-2,8-ketosidically linked polysialosyl units were developed to identify and study the temporal expression of these unique carbohydrate moieties in developing neural tissue. Sialic acid incorporated into adult rat brain membranes was resistant to endoneuraminidase, indicating that the poly-α-2,8-sialosyl sialyltransferase activity is restricted to an early developmental epoch. The product of this reaction was also sensitive to endoneuraminidase and contained α-2,8-linked polysialosyl chains, thus showing that N-CAM can serve as an exogenous acceptor for sialylation in vitro. The addition of a partially purified preparation of chick N-CAM to the membranous sialyltransferase stimulated sialic acid incorporation 3-fold. This was confirmed by structural studies which showed that the endoneuraminidase-sensitive brain material consisted of multimers of sialic acid. A bacteriophage-derived endoneuraminidase specific for polysialic acid was used to demonstrate that at least 20-30% of the NeuNAc was incorporated into α-2,8-linked polysialosyl units. In sodium dodecyl sulfate-polyacrylamide gels, the major radiolabeled species migrated with a mobility expected for N-CAM. ![]() At pH 6.0, 84 pmol of NeuNAc mg of protein -1 h -1 were incorporated. A Golgi-enriched fraction from 20-day-old fetal rat brain contains a membrane-associated sialyltransferase that catalyzes the incorporation of N-acetylneuraminic acid (NeuNAc) from CMP-NeuNAc into polymeric products. These polysialosyl units cap N-linked oligosaccharides of the complex-type on neural cell adhesion molecules (N-CAM). ![]() ![]() Prokaryotic derived probes that specifically recognize α-2,8-ketosidically linked polysialosyl units were developed to identify and study the temporal expression of these unique carbohydrate moieties in developing neural tissue.
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