The enzymatic synthesis of lipid A: molecular structure and biologic function of monosaccharide precursors.

Certain Escherichia coli mutants, deficient in phosphatidylglycerol, accumulate novel, glucosamine-derived phospholipids that appear to be very early precursors of lipid A. The simplest of these, lipid X, is a derivative of glucosamine-1-phosphate substituted with beta-hydroxymyristoyl moieties at positions 2 and 3. The discovery of lipid X makes it possible to predict a biosynthetic pathway and a unified structure for lipid A. In addition, the minimal molecular requirements for the mitogenic and endotoxic properties of lipopolysaccharides can be elucidated with compounds of this kind.