ABSTRACT
The in vitro biosynthesis of teichuronic acid, the cell wall polysaccharide of Micrococcus lysodeikticus, occurs in two stages. In the initial stage, the particulate enzyme fraction utilizes uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) and uridine diphosphate N-acetylmannosaminuronic acid (UDP-ManNAcUA) to form three intermediates. N-Acetylglucosamine is transferred from UDP-GlcNAc to a carrier lipid present in the particulate enzyme fraction to form the first intermediate, GlcNAc carrier lipid. N-Acetylmannosaminuronic acid is then transferred from UDP-ManNAcUA to the GlcNAc carrier lipid to form ManNAcUA-GlcNAc carrier lipid, the second intermediate. Finally, the transfer of an additional N-acetylmannosaminuronic acid residue from UDP-ManNAcUA yields the third intermediate, (ManNAcUA)2-GlcNAc carrier lipid. Reactions involving UDP-ManNAcUA release uridine diphosphate. Concomitant synthesis of peptidoglycan or membrane mannan inhibits the synthesis of the teichuronic acid intermediates, thereby providing indirect evidence that the carrier lipid is undecaprenol monophosphate.
