| Abstract: | The membrane fraction from a mutant of Salmonella anatum deficient in UDPgalactose-4-epimerase, utilized synthetic ficaprenyl alpha-D-galactosyl diphosphate as a substrate in the biosynthesis of the O-polysaccharide portion of lipopolysaccharide which has a mannosylrhamnosylgalactose repeating sequence. The galactosyl lipid was prepared by chemical synthesis from D-galactose and ficaprenol extracted from Ficus elastica. Membrane preparations catalyzed the transfer of rhamnose from TDP-rhamnose onto membrane-bound ficaprenyl galactosyl diphosphate forming rhamnosylgalactosyl ficaprenyl diphosphate; the reaction was dependent on the prior insertion of the synthetic glycosyl-lipid into the membrane, and was proportional to incubation time up to 4 min at 29 degrees C. When both TDP-rhamnose and GDP-mannose were added, the product formed was O-polysaccharide. These results indicate that the chemically synthesized ficaprenyl galactosyl diphosphate can be an active substrate for the in vitro synthesis of the Salmonella O-polysaccharide. |
