1. Phosphatidate phosphohydrolase from the particle-free supernatant of rat liver was assayed by using emulsions of phosphatidate as substrate. 2. The inhibition of the phosphohydrolase by chlorpromazine was of a competitive type with respect to phosphatidate. The potency of various amphiphilic cationic drugs as inhibitors of this reaction was related to their partition coefficients into a phos...

For a purified preparation of the soluble form of phosphatidate phosphohydrolase (EC 3.1.3.4) from guinea pig cerebral cortex, I-O-alkyl-racglycerol 3-phosphate was found to be accepted as a substrate. This substrate analog was tritium-labeled in order to serve in a rapid sensitive assay for the enzyme, in which labeled I-alkyl glycerol is released. Heat denaturation and enzyme activity depende...

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...

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...

Phosphatidate phosphohydrolase (EC 3.1.3.4) activity can be found in late gestational human amniotic fluid and is thought to originate in type II alveolar cells of the fetal lungs where it plays an important role in lung surfactant synthesis. In the present study, phosphatidate phosphohydrolase activity was detected and characterized in a 105 000 X g pellet of amniotic fluid using either [32P]p...

Activities of phosphatidate phosphohydrolase and palmitoyl-CoA hydrolase were determined in cardiac subcellular fractions prepared from rabbits which had received tri-iodothyronine and from hamsters with hereditary cardiomyopathy (strain BIO 14.6). 1. Both mitochondrial and microsomal fractions of hyperthyroid rabbit hearts produced 4-5 times as much diacylglycerol 3-phosphate from glycerol 3-p...

The mechanisms behind the hypotriglyceridemic effect of 1,10-bis(carboxymethylthio)decane (3-thiadicarboxylic acid) and tetradecylthioacetic acid and the development of fatty liver caused by 3-tetradecylthiopropionic acid (Aarsland et al. 1989. J. Lipid Res. 30: 1711-1718.) were studied in the rat. Repeated administration of S-substituted non-beta-oxidizable fatty acid analogues to normolipidem...

cell lines, whereas alkaline phosphohydrolase activity was 8 times greater in Sarcoma 180/TG. Alkaline phosphohydrolase activity was localized predominantly in particulate fractions from Sarcoma 180/TG, showed a pH optimum of 9.2, and hydrolyzed a wide variety of phosphate esters, including p-nitropheny (phosphate and 5'-nucleotides, such as 6-thioinosine 5'-phosphate. It is suggested that enha...

With isolated liver microsomes, both synthetic and hydrolytic activities of glucose-6-phosphatase (D-ghcase-6-phosphate phosphohydrolase, EC 3.1.3.9) are characterized by considerable latency (ie activity manifest only in the presence of detergent). Believing that latency may relate to the morphological state of the cellular structure to which the enzyme is bound, we have performed studies to d...