The properties and subcellular distribution of phosphatidate phosphatase (EC 3.1.3.4) from adipose tissue have been investigated. The enzyme was assayed using both aqueous phosphatidate and membrane-bound phosphatidate as substrates. When measured with aqueous substrate, activity was detected in the mitochondria, the microsomes, and the soluble fraction. Mg(2+) at low concentration stimulated t...

The regulation of Saccharomyces cerevisiae membrane-associated phosphatidate phosphatase (3-sn-phosphatidate phosphohydrolase, EC 3.1.3.4) activity by sphingoid bases was examined using Triton X-100/lipid-mixed micelles. Sphingosine, phytosphingosine, and sphinganine inhibited purified preparations of the 104- and 45-kDa forms of phosphatidate phosphatase in a dose-dependent manner. The structu...

Phosphatidate is an intermediate in the biosynthesis of diacylglycerol, triacylglycerol, phosphatidylethanolamine, phosphatidylcholine and CDP-diacylglycerol. In addition, phosphatidate may be subject to degradation by particulate phospholipases. The factors regulating the disposition of phosphatidate have interested numerous investigators. We have studied the reactions of phosphatidate metabol...

Changes in nuclear size and shape during the cell cycle or during development require coordinated nuclear membrane remodeling, but the underlying molecular events are largely unknown. We have shown previously that the activity of the conserved phosphatidate phosphatase Pah1p/Smp2p regulates nuclear structure in yeast by controlling phospholipid synthesis and membrane biogenesis at the nuclear e...

The influence of phospholipids on the activity of the soluble phosphatidate phosphohydrolase from rat liver was studied. Phosphatidylethanolamine stimulated the enzyme activity whereas phosphatidylglycerol, phosphatidylserine, and phosphatidylinositol were inhibitory. At a phospholipid concentration of 0.7 mg/ml, phosphatidylglycerol inhibited phosphatidate phosphohydrolase activity by 75%, whi...

Lung contains both Mg2+-dependent and Mg2+-independent phosphatidate phosphohydrolase activities. Addition of Triton X-100 (0.5%) or chlorpromazine (1 mM) leads to a marked increase in the total phosphatidate phosphohydrolase activity in rat lung microsomes (microsomal fractions), but a decrease in the Mg2+-dependent activity. These observations suggest that the Mg2+-independent activity is sti...

Phosphatidate-dependent protein phosphorylation was observed in soluble extracts from rat liver, brain, lung, and testis. The phosphorylation was stimulated by free Ca2+ in the range of 360-800 nM. Incubation mixtures containing phosphatidate provided markedly different profiles of protein phosphorylation from those with phosphatidylserine plus 1,2-diolein. Phosphatidate-dependent phosphorylati...

Carbamylcholine enhances the labeling of phosphatidate and phosphatidylinositol from 32Pi in nerve endings. Approximately 74% of labeled phosphatidate and 85% of labeled phosphatidylinositol produced on muscarinic stimulation are accounted for by tetraenoic species, as detected by argentation TLC. Incubation of membranes derived from nerve endings with [gamma-32P]ATP under conditions of phospho...

Obesity in obese-hyperglycaemic mouse is associated with an increase in number and size of adipocytes. Adipocytes from the obese mouse showed increased incorporation of [14C]acetate and[14C]glucose into triacylglycerol. This increased capacity of triacylglycerol formation was correlated with increased activities of various triacylglycerol-forming enzymes measured in the microsomal fraction of a...

The malachite green-molybdate reagent was used for a colorimetric assay of pure Mg2(+)-dependent phosphatidate phosphatase activity. This enzyme plays a major role in fat metabolism. Enzyme activity was linear with time and protein concentration, and with the concentration of water-soluble dioctanoyl phosphatidate. The colorimetric assay was used to examine enzyme inhibition by phenylglyoxal, p...