title: Chloroform-soluble nucleotides in Escherichia coli. Role of CDP-diglyceride in the enzymatic cytidylylation of phosphomonoester acceptors.
abstract: CDP-diglyceride, the precursor of all the phospholipids in Escherichia coli, is cleaved in vitro to phosphatidic acid and CMP by a membrane-bound hydrolase. Since the physiological function of CDP-diglyceride hydrolase is unknown, we have explored the possibility that this enzyme acts in vivo as either a phosphatidyl- or cytidylyltransferase. To distinguish between these two alternatives, partially purified hydrolase was incubated with CDP-diglyceride in the presence of 50% H218O. Analysis of the reaction products by 31P NMR showed that 18O is incorporated exclusively into CMP, suggesting that the enzyme is a cytidylyltransferase. This conclusion is further supported by the following experimental results: (i) the hydrolase catalyzes the transfer of CMP from CDP-diglyceride to Pi; (ii) numerous phosphomonoesters, such as glycerol 3-phosphate, phosphoserine, and glucose 1-phosphate also function as CMP acceptors, but the corresponding compounds lacking the phosphate residues are not substrates for the enzyme; and (iii) CDP-diglyceride hydrolase exchanges [32P]phosphatidic acid for the phosphatidyl moiety of CDP-diglyceride and 32Pi for the beta-phosphate residue of CDP, indicating the involvement of a novel CMP-enzyme complex. These data suggest a biosynthetic role for CDP-diglyceride hydrolase, and extend the possible functions of CDP-diglyceride in the E. coli envelope.
mesh_terms: D002725:Chloroform; D003567:Cytidine Diphosphate Diglycerides / Q000378:metabolism*; D003568:Cytidine Monophosphate / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics*; D006867:Hydrolases / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D009702:Nucleoside Diphosphate Sugars / Q000378:metabolism*; D009711:Nucleotides / Q000378:metabolism*; D010712:Phosphatidic Acids / Q000378:metabolism; D012995:Solubility
chemical_list: D003567:Cytidine Diphosphate Diglycerides; D009702:Nucleoside Diphosphate Sugars; D009711:Nucleotides; D010712:Phosphatidic Acids; D002725:Chloroform; D006867:Hydrolases; D003568:Cytidine Monophosphate