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...

The two purified nucleoside triphosphate phosphohydrolases from vaccinia virus are distinct enzymes as judged by their nucleotide substrate and polynucleotide cofactor specificities. Phosphohydrolase I hydrolyzes only ATP and dATP, whereas phosphohydrolase II hydrolyzes the four common ribonucleoside triphosphates as well as dATP and TTP. The range of K, values for ATP and dATP hydrolysis by ph...

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...

Although adenine-requiring auxotrophs of Bacillus subtilis accumulate large quantities of inosine or hypoxanthine, or of both, they do not accumulate inosine-5'-monophosphate (IMP). Experiments directed at understanding this phenomenon were conducted with an adenineless auxotroph and with a mutant derived from it which lacked alkaline phosphohydrolase. It was found that B. subtilis contains fou...

The subcellular distribution of Mg2+-dependent phosphatidate phosphohydrolase in rat adipocytes between a soluble and a membrane-bound fraction was measured by using both centrifugal fractionation and a novel Millipore-filtration method. The relative proportion of the phosphohydrolase associated with the particulate fraction was increased on incubation of cells with noradrenaline or palmitate. ...

Sphingosine 1-phosphate (S1P) is a bioactive lipid molecule that acts as both an extracellular signaling mediator and an intracellular second messenger. S1P is synthesized from sphingosine by sphingosine kinase and is degraded either by S1P lyase or by S1P phosphohydrolase. Recently, mammalian S1P phosphohydrolase (SPP1) was identified and shown to constitute a novel lipid phosphohydrolase fami...

Assays for two distinct phosphatidate phosphohydrolase activities were established based upon a differential inhibition by N-ethylmaleimide (NEM). The activity that is insensitive to this reagent in rat liver is predominantly in the plasma membrane fraction, whereas the NEM-sensitive activity is in the cytosolic and microsomal fractions. The NEM-insensitive activity is further distinguished fro...

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...

The deoxythymidylate phosphohydrolase (dTMPase) induced by Bacillus subtilis bacteriophage PBS2 (whose DNA contains uracil instead of thymine) has been partially purified and shown to possess deoxyuridylate phosphohydrolase (dUMPase) activity. The similarities of induction period, pH dependence, heat and trypsin inactivation, sulfhydryl reagent and fluoride inhibition, metal ion effects, kineti...

The two nucleic acid-dependent nucleoside triphosphate phosphohydrolases, previously purified from vaccinia virus cores, were shown to be immunologically distinct enzymes. Antiserum prepared against purified phosphohydrolase I and antiserum prepared against purified phosphohydrolase II only neutralized the activity of that enzyme used as antigen. Both enzymes were induced in HeLa cells after va...