title: Partial purification, properties, and subcellulsr distribution of rat liver phosphatidate phosphatase.
abstract: Phosphatidate phosphatase (EC 3.1.3.4Y was purified 15- to 20-fold from the soluble fraction of rat liver. The purification procedure involved calcium phosphate gel adsorption and elution, ammonium sulfact precipitation, and molecular-sieve chromatography. For the enzyme assay, and aqueous dispersion of phosphatidate, rather than "membrane-bound" phosphatidate, was used as substrate. The partially purified enzyme depends almost entirely on the presence of Mg2+ for its activity. Morover, the activity of the enzyme is stimulated by phosphatidylcholine. The enzyme exhibits a high substrate specificity for phosphatidate. The apparent Km for phosphatidate is approximately 0.05 mM. The optimum pH is between 7.4 and 7.6. The enzyme is inhibited by fluoride and by p-chloromercuribenzoate. The subcellular distribution of phosphatidate phosphatase in rat liver was studied by assaying the activity of the enzyme in the presence of Mg2+ and phosphatidylcholine. In contrast ot the results of previous studies, most of the enzyme activity was found in the soluble fraction.
mesh_terms: D000327:Adsorption; D000645:Ammonium Sulfate; D000818:Animals; D002729:Chloromercuribenzoates / Q000494:pharmacology; D002855:Chromatography, Thin Layer; D004789:Enzyme Activation; D005459:Fluorides / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008099:Liver / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D010712:Phosphatidic Acids; D010713:Phosphatidylcholines / Q000494:pharmacology; D010744:Phosphoric Monoester Hydrolases / Q000032:analysis / Q000037:antagonists & inhibitors / Q000302:isolation & purification*; D051381:Rats
chemical_list: D002729:Chloromercuribenzoates; D010712:Phosphatidic Acids; D010713:Phosphatidylcholines; D010744:Phosphoric Monoester Hydrolases; D008274:Magnesium; D005459:Fluorides; D000645:Ammonium Sulfate