It is becoming evident that increased cellular glucose concentration leads to an increase in UDP-β-N-Acetylglucosamine (UDP-GlcNac) concentration and O-GlcNacylation of many proteins. This study demonstrates that glycogenin, an autoglucosylating protein, utilizes UDP-GlcNac as its substrate to incorporate 0.5 mole of GlcNAc onto itself. The presence of incorporated GlcNac into glycogenin was confirmed by HPAEC-PAD (High-Performance Anion Exchange Chromatography and Pulsed Amperometric Detection) and by radiolabeling with galactosyltransferase. The results suggest that GlcNac is added to Tyr194 either as a first residue or to the growing oligosaccharide. Furthermore, the recombinant glycogenin modified with GlcNac was still able to autoglucosylate. However, GlcNac modified glycogenin subunit of glycogen synthase was resistant to the addition of glucose by glycogen synthase. These results suggest that O-GlcNacylation of glycogenin may inhibit glycogen synthase activity, resulting in inhibition of glycogenesis.
|School:||California State University, Long Beach|
|School Location:||United States -- California|
|Source:||MAI 48/04M, Masters Abstracts International|
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