The longterm objective of this project is to develop novel antibacterial agents which disable the synthesis of lipopolysaccharides (LPS), also known as endotoxins. LPS molecules which are components of the outer membrane of Gram-negative bacteria contribute to the structural integrity of the membrane and hence are essential to bacterial viability. In addition, LPS molecules are responsible for many of the pathophysiological effects Gram-negative bacteremia. Therefore the biosynthesis of LPS represents a target for pharmacological attack. The biosynthesis of LPS begins with the formation of the precursor, lipid A. Recently the pathway for the synthesis of lipid A has been elucidated. One of the first steps in this pathway is catalyzed by a disaccharide synthase which has been purified and the gene encoding it cloned. We propose to develop substrate analogs which effectively inhibit this enzyme. An inhibitor that prevented the action of this enzyme in bacteria would disrupt membrane biogenesis and thus act as an antibiotic. In order to develop such an inhibitor we will undertake to:1. chemically synthesize six analogs of lipid X a substrate of lipid A disaccharide synthase.2. Evaluate synthetic substrate analogs of this enzyme as potential inhibitors using a novel, rapid, non-radiochemical spectrophotometric assay.3. Perform bacterial uptake studies on radiolabeled lipid X in order to determine its permeability with respect to intact bacteria.POTENTIAL COMMERCIAL APPLICATION: The proposed commercial application of this research is the development of a class of drugs, specifically Gram- negative specific antibiotics, with a novel mechanism of action. The target of these drugs would be the bacterial enzyme, lipid A disaccharide synthase, which synthesizes the lipopolysaccharide precursor lipid A.National Institute of Allergy and Infectious Diseases (NIAID)
