The enzymes of lecithin biosynthesis in human neonatal lungs. IV. Phosphorylcholine cytidyltransferase.
Phosphorylcholine cytidyltransferase, the enzyme which catalyzes the transfer of phosphorylcholine to cytidine 5'-triphosphate to form CDP-choline, was studied for the first time in human neonatal lung. The assay of product synthesis was linear for 10-20 min and up to 12 mg protein. The pH optimum was 6-6.5. The Km of CTP was 2.0 times 10- minus 3 M, and the Km of phosphorylcholine was 0.25 times 10- minus 3 M. The true Vmax was 10 nmol CDP-choline/mg protein/10 min. The enzyme was stable under frozen conditions. Oxygen had no apparent affect on enzyme activity.
D002794:Choline / Q000031:analogs & derivatives / Q000032:analysis; D003597:Cytosine Nucleotides / Q000032:analysis / Q000096:biosynthesis; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007231:Infant, Newborn; D008168:Lung / Q000196:embryology / Q000201:enzymology*; D009713:Nucleotidyltransferases / Q000032:analysis*; D010100:Oxygen / Q000494:pharmacology; D010713:Phosphatidylcholines / Q000096:biosynthesis*; D011663:Pulmonary Surfactants / Q000032:analysis; D012127:Respiratory Distress Syndrome, Newborn
D003597:Cytosine Nucleotides; D010713:Phosphatidylcholines; D011663:Pulmonary Surfactants; D009713:Nucleotidyltransferases; D002794:Choline; D010100:Oxygen