Chemical Structure of Lipid A Isolated from Flavobacterium meningosepticum Lipopolysaccharide

Abstract

ABSTRACT The chemical structure of the lipid A of the lipopolysaccharide component isolated from Flavobacterium meningosepticum IFO 12535 was elucidated. Methylation and nuclear magnetic resonance analyses showed that two kinds of hydrophilic backbone exist in the free lipid A: a β (1→6)-linked 2-amino-2-deoxy- d -glucose, which is usually present in enterobacterial lipid A’s, and a 2-amino-6- O -(2,3-diamino-2,3-dideoxy-β- d -glucopyranosyl)-2-deoxy- d -glucose, in a molar ratio of 1.00:0.35. Both backbones were α-glycosidically phosphorylated in position 1, and the hydroxyl groups at positions 4, 4′, and 6′ were unsubstituted. Liquid secondary ion-mass spectrometry revealed a pseudomolecular ion at m/z 1673 [M-H] − as a major monophosphoryl lipid A component carrying five acyl groups. Fatty acid analysis showed that the lipid A contained 1 mol each of amide-linked ( R )-3-OH iC 17:0 , ester-linked ( R )-3-OH iC 15:0 , amide-linked ( R )-3- O -(iC 15:0 )-iC 17:0 , and both amide- and ester-linked ( R )-3-OH C 16:0 . Fatty acid distribution analyses using several mass spectrometry determinations demonstrated that the former two constituents were distributed on positions 2 and 3 of the reducing terminal unit of the backbones and that the latter two were attached to the 2′ and 3′ positions in the nonreducing terminal residue.