the mechanism by which bi-and trivalent cations affect human liver phosphatidatephosphohydrolase (pap) activity was investigated. bivalent cations up to 1 mm increased pap activity whereas at higher concentrations the activity of the enzyme decreased. the stimulatory concentration for trivalent cations such as al3+ and cr3+, however, was much lower being 2 m m and 1 m m, respectively. all catio...

phosphatidate phosphohydrolase (pap2b, fraction b) was purified from the plasma membrane ofrat liver cells. the km for the surface concentration of phosphatidic acid was 0.43 mol%. the subunit of theenzyme had an m.w. of 33.8 kda using sodium dodecyl sulfate polyacrylamide gel electrophoresis. thenative enzyme shows a molecular weight of 182 kda in a gel filtration column packed with sephacryl ...

objective(s) phosphatidate phosphohydrolase (pap) catalyzes the dephosphorylation of phosphatidic acid to yield pi and  diacylglycerol. two different forms of pap in rat hepatocyte have been reported. pap1 is located in cytosolic and microsomal fractions and participates in the synthesis of triacylglycerols, phosphatidylcholine, and phosphatidylethanolamine, whereas the other form of phosphatid...

At 24-26 degrees C, force-area isotherms show that unionized dipalmitoyl phosphatidic acid forms a solid-condensed film while unionized egg and dioleoyl phosphatidic acids form liquid-expanded films. Surface area is a characteristic feature of a specific phosphatidic acid and the purity of a phosphatidic acid preparation can be established by the surface area of the unionized phosphatidic acid ...

Phosphatidic acid added to the medium markedly elevated intracellular cyclic GMP content in cultured neuroblastoma N1E 115 cells. There was a significant elevation of cyclic GMP with 1 micrograms/ml and a maximum (70-fold) elevation with 100 micrograms/ml of phosphatidic acid. Other natural phospholipids did not increase, or increased only slightly, the cyclic GMP content in the cells. The elev...

Acetylcholine, which stimulates NaCl secretion in the avian salt gland, causes the rapid formation of a fraction of phosphatidic acid, as measured by (32)P incorporation, which amounts maximally to about 0.18 micromoles per g of fresh tissue. This does not appear to involve synthesis of the diglyceride moiety of phosphatidic acid, as measured by glycerol-1-(14)C incorporation. It presumably inv...

Sphingosine, a breakdown product of cellular sphingolipids, has recently been shown to stimulate DNA synthesis and act synergistically with known growth factors to induce proliferation of quiescent Swiss 3T3 fibroblasts (Hong, Z., Buckley, N. E., Gibson, K., and Spiegel, S. (1990) J. Biol. Chem. 265, 76-81). The present study demonstrates that mitogenic concentrations of sphingosine induce earl...

The administration of phosphatidic acid to rat livers perfused with media containing either 1.3 mM- or 10 microM-Ca2+ was followed by a stimulation of Ca2+ efflux, O2 uptake and glucose output. The responses elicited by 100 microM-phosphatidic acid were similar to those induced by the alpha-adrenergic agonist phenylephrine. Contrary to suggestions that phosphatidic acid acts like a Ca2+-ionopho...

Activation of platelets induces the formation of phosphatidic acid, which results from the combined actions of a phosphatidylinositol-specific phospholipase C and a 1,2-diacylglycerol kinase. It has been proposed that this phosphatidic acid leads in some way to the subsequent production of arachidonic acid. The present studies reveal the existence of a particulate phospholipase Az enzyme that a...

Microsomal membrane preparations from the developing seeds of sunflower (Helianthus annuus L.) catalyse the conversion of sn-glycerol-3-phosphate and acyl-CoA to triacylglycerol via phosphatidic acid and diacylglycerol. The formation of diacylglycerol from phosphatidic acid was Mg2+ dependent and in the presence of EDTA phosphatidic acid accumulated. This property was used to generate large qua...