Enzymatic formation of acetylgalactosamine.

Several papers have been published on the biosynthesis of glucosamine in different organisms (l-3), but the reactions which lead to the synthesis of galactosamine have hardly been explored. The first indication of its mode of synthesis came from the isolation of uridine diphosphate’ acetylgalactosamine from liver by Pontis (4). This finding showed that the transformation of acetylhexosamines is similar to that of the pair glucosegalactose which has been studied in detail (5, 6). Pontis mentioned that, upon incubation of UDP-acetylglucosamine with a crude liver extract, some acetylgalactosamine was formed, but he did not investigate whether the substance appeared in the free or combined form. Further work on the point is reported in this paper. The products arising by the action of rat liver homogenate on UDP-acetylglucosamine were found to be free acetylgalactosamine and uridine monophosphate.