LIPID-PHOSPHOACETYLMURAMYL-PENTAPEPTIDE AND LIPID-PHOSPHODISACCHARIDE-PENTAPEPTIDE: PRESUMED MEMBRANE TRANSPORT INTERMEDIATES IN CELL WALL SYNTHESIS

Abstract
Cell wall glycopeptide in Staphylococcus aureus or Micrococcus lysodeikticus is synthesized in a reaction using uridine-diphosphate (UDP)-acetylmuramyl-pentapeptide and UDP-acetyl-glucosamine as substrates. Inorganic phosphate and uridine-monophos-phate (UMP) are the other products formed from the former substrate while UDP is formed from the latter. The mechanism of the reaction is transfer of phosphoacetylmuramyl-pentapeptide to lipid, formation of acetylglucosaminyl-acetylmuramyl(-penta-peptide)-P-lipid and transfer of the disaccharide-pentapeptide to an acceptor (presumably an incomplete glycopeptide) with release of inorganic phosphate and presumably of lipid. It is probably on example of a cellular transport mechanism. Vancomycin and ristocetin which are specific inhibitors of glycopeptide synthesis do not interfere with formation of the lipid intermediates. Their locus of action is in the utilization of lipid-phos-phodisaccharide-pentapeptide for glycopeptide synthesis.