In vitro deacylation of lipopolysaccharide of Salmonella minnesota by Acanthamoeba castellanii enzymes.

Enzymatic deacylation of the lipopolysaccharide isolated from a Salmonella Rd mutant by a cell-free preparation from Acanthamoeba castellanii has been studied. The degradation was found to be dependent on the presence of a surface-active component (Triton X-100) in the reaction mixture. The lipid A part of the lipopolysaccharide was the primary target of the enzymes, which cleaved with high efficiency the ester-bound long-chain nonhydroxylated and 3-hydroxylated acyl residues, i.e. lauric, myristic, palmitic and 3-hydroxymyristic acid. The cell-free preparation also exhibited amidase activity cleaving about 50% of the amide-bound 3-hydroxymyristic acid residues. In addition the extract proved to possess phosphatase activity liberating ester-bound and glycosidically bound phosphate groups of lipid A. On the other hand, the glucosaminyl-beta 1,6-glucosamine disaccharide was not degraded and remained bound to the oligosaccharide part (heptose/3-deoxyoctulosonic acid) of the lipopolysaccharide.