Structural studies on the non‐toxic lipid A from Rhodopseudomonas sphaeroides ATCC 17023

Abstract

The lipid A isolated from Rhodopseudomonas sphaeroides ATCC 17023 has been investigated. A sequence of analyses indicated β‐D‐glucosaminyl‐1,6‐D‐glucosamine as the sugar backbone carrying phosphate groups at C‐1 of the reducing glucosamine and C‐4 of the non‐reducing glucosamine. Both 3‐(7‐tetradecenoyl)oxytetradecanoic and 3‐oxotetradecanoic acid are linked to the NH₂ groups. Two residues of 3‐hydroxydecanoic acid are linked to hydroxy groups at C‐3 of both reducing and non‐reducing glucosamine, and the hydroxy group of 3‐hydroxydecanoic acid is free. In free lipid A, the hydroxy group at C‐4 of the reducing glucosamine and at C‐6 of the non‐reducing glucosamine are unsubstituted. The latter probably arises from a 3‐deoxy‐D‐manno‐octulosonate linkage. The structural similarities and dissimilarities existing between lipid A of R. sphaeroides, which is non‐toxic, and lipid A types such as those from Salmonella, which are toxic, are discussed.