[
Trends Biochem Sci,
2006]
Phosphatidate phosphatase (PAP) enzymes catalyze the dephosphorylation of phosphatidate, yielding diacylglycerol and inorganic phosphate. In eukaryotic cells, PAP activity has a central role in the synthesis of phospholipids and triacylglycerol through its product diacylglycerol, and it also generates and/or degrades lipid-signaling molecules that are related to phosphatidate. There are two types of PAP enzyme, Mg(2+) dependent (PAP1) and Mg(2+) independent (PAP2), but only genes encoding PAP2 enzymes had been identified until recently, when a gene (PAH1) encoding a PAP1 enzyme was found in Saccharomyces cerevisiae. This discovery has revealed a molecular function of the mammalian protein lipin, a deficiency of which causes lipodystrophy in mice. With molecular information now available for both types of PAP, the specific roles of these enzymes in lipid metabolism are being clarified.
[
Ann N Y Acad Sci,
1959]
A detailed summary of methods for axenic cultivation of Caenorhabditis briggsae is given. Results of axenic culture on chemically defined basal media (GM and GS) and on these media supplemented with undefined preparations of horse liver and chick embryos are reported in detail, with a review of the formulation of the GM and GS designs and of the chronology of changes made therein. The best growth so far realized with C. briggsae in axenic culture is suboptimal as compared with growth in the presence of bacteria, and maturation takes longer (4 to 5 days instead of about 3 days at 20C). Suitable media of the GM design give good axenic growth with relatively low levels of complex supplements-Liver Protein Fraction C (LPF-C) and chick embryo extract (CEE), both of which presumably include a protein-linked requirement, Factor Rb. With GM-16 plus CEE or certain GSs plus CEE, requirements have been variously demonstrated for 6 B-vitamins: folic acid, niacinamide, pantothenic acid, pyridoxine, riboflavin, and thiamine; one of these-folic acid-had already been shown to be required. Only niacinamide is also demonstrated as a requirement in the presence of low levels of LPF-C. In the presence of CEE we have tested the essentiality of the other 5 vitamins only by omitting them singly from vitamin mixes added at increased (5 to 50 times GS) levels to media of GM or GS type. Preliminary evidence is given that the ten "rat-essential" amino acids are required. Improvement of nutritional balance with respect to amino acid levels and to relative levels of amino acids in relation to vitamins or salts is discussed as an explanation of differential growth on different media. Possibly the variations of DM-GS so far tested contain unnecessarily high amino acid levels. The definition of nutritional requirements for C. briggsae still presents many