Proceedings of the National Academy of Sciences

By F. Whipple. 1914

The structure of hyaluronic acid has been elucidated largely by the work of Meyer and collaborators,1' 2, I who have shown it to be a linear polymer of alternating units of N-acetyl-D-glucosamine and D-glucuronic acid. The monosaccharide components appear to be combined in alternating f8-1,3and p-1,4linkages, the former being those involving C1 of GA4 and the latter those involving Cl of AG. Hyaluronic acid isolated from different tissues appears to have constant chemical composition3' L 6 but varies in average molecular weight from 300,000 to 1,500,000.7 No enzymatic synthesis of hyaluronic acid by cell-free preparations has been reported. We have now been able to demonstrate the synthesis of oligosaccharide chains having the structure of hyaluronic acid by using cell-free homogenates of the Rous chicken sarcoma,8 a tissue which has been known for a long time to produce large quantities of the mucopolysaccharide6 9, 10 and to have very little if any active hyaluronidase.10 Synthesis of the oligosaccharides has been shown by incubating sarcoma homogenates with uridine diphospho-N-acetyl-glucosamine labeled with C14 in the N-acetyl group, together with uridine diphosphoglucuronic acid or with uridine diphosphoglucose and diphosphopyridine nucleotide. In some experiments the homogenates were incubated with uridine triphosphate and N-acetyl-glucosamine-6-phosphate labeled with C14 in the N-acetyl group. The preparation of the latter material with a specific yeast N-acetylase has been described.11 UDPAg was discovered by Leloir and co-workers,12' 13 but no coenzymatic function for it was demonstrated. UDPGA has been isolated and found to be the substrate for glucuronide synthesis by liver extracts.'4' 15 The formation of UDPGA by enzymatic oxidation of UDPG in the presence of DPN has been described by Kalckar and coworkers.16 Evidence discussed below indicates that UDPAg and UDPGA are the substrates from which hyaluronic acid chains are synthesized.

Subfields: Statistics and Probability

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