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The hybrid cell B6 line, which synthesizes large amounts of hyaluronate as the predominant glycosaminoglycan, was grown in the presence of 3Hglucosamine. The 3Hhyaluronate has a high molecular weight and was excluded by Sephacryl S-1000. After disruption of the cells the 3Hhyaluronate could further be elongated by incubation with UDP-GlcNAc and UDP-14CGlcA, yielding a hybrid molecule of hyaluronate labelled with 3HGlcNAc and 14CGlcA. Treatment of the cells with hyaluronidase before disruption eliminated the large 3Hhyaluronate and elongation of nascent chains in vitro commenced from low-molecular-weight chains. Thus nascent hyaluronate chains were degraded extracellularly by hyaluronidase and were therefore synthesized at the inner side of plasma membranes and extruded to the cell surface.
Peter Prehm (Fri,) studied this question.