Inhibition of in vitro peptidoglycan biosynthesis in Escherichia coli by guanosine 5'-diphosphate 3'-diphosphate.

Physiological concentrations of guanosine 5'-diphosphate 3'-diphosphate (ppGpp) inhibited the synthesis of lipid intermediates and peptidoglycan catalyzed by a particulate enzyme preparation from Escherichia coli. The inhibition of these reactions was dependent on the concentrations of ppGpp and MgCl2 in the assay. The degree of inhibition of lipid intermediate synthesis decreased as the molar ratio of MgCl2 to ppGpp was increased, and no inhibition was observed above a MgCl2 to ppGpp ratio of 2.5. The synthesis of peptidoglycan was more sensitive to inhibition by ppGpp, and significant inhibition occurred under conditions where lipid intermediate synthesis was unaffected (i.e., at MgCl2 to ppGpp ratios of 2.5 or more). A variety of other nucleotides did not inhibit the synthesis of lipid intermediates and peptidoglycan.