The involvement of guanosine 5-diphosphate-3-diphosphate in the regulation of phospholipid biosynthesis in Escherichia coli. Lack of ppGpp inhibition of acyltransfer from acyl-ACP to sn-glycerol 3-phosphate.

The response of the Escherichia coli sn-glycerol-3-phosphate acyltransferase to guanosine 5-diphosphate-3-diphosphate (ppGpp) has been determined in vitro employing palmityl coenzyme A (CoA) and palmityl acyl carrier protein as acyl substrates. Levels of ppGpp which cause significant inhibition of enzyme activity with palmityl-CoA as substrate have no effect on enzyme activity when palmityl acyl carrier protein is employed as acyl donor. The inhibition of enzyme activity observed with palmityl-CoA as acyl substrate was dependent upon the relative concentrations of MgCl2 and ppGpp (MgCl2 to ppGpp ratio) employed. With palmityl-CoA as acyl donor, PPGpp inhibited the production of lysophosphatidic acid but not phosphatidic acid. With palmityl acyl carrier protein as acyl substrate, ppGpp had no influence upon the distribution of the reaction products.