Publications

• Enzymological properties of the LPP1-encoded lipid phosphatase from Saccharomyces cerevisiae.

  Furneisen J.M., Carman G.M.

  The product of the LPP1 gene in Saccharomyces cerevisiae is a membrane-associated enzyme that catalyzes the Mg(2+)-independent dephosphorylation of phosphatidate (PA), diacylglycerol pyrophosphate (DGPP), and lysophosphatidate (LPA). The LPP1-encoded lipid phosphatase was overexpressed 681-fold in ... >> More

  The product of the LPP1 gene in Saccharomyces cerevisiae is a membrane-associated enzyme that catalyzes the Mg(2+)-independent dephosphorylation of phosphatidate (PA), diacylglycerol pyrophosphate (DGPP), and lysophosphatidate (LPA). The LPP1-encoded lipid phosphatase was overexpressed 681-fold in Sf-9 insect cells and used to examine the enzymological properties of the enzyme using PA, DGPP, and LPA as substrates. The optimum pH values for PA phosphatase, DGPP phosphatase, and LPA phosphatase activities were 7. 5, 7.0, and 7.0, respectively. Divalent cations (Mn(2+), Co(2+), and Ca(2+)), NaF, heavy metals, propranolol, phenylglyoxal, and N-ethylmaleimide inhibited the PA phosphatase, DGPP phosphatase, and LPA phosphatase activities of the enzyme. The inhibitory effects of N-ethylmaleimide and phenylglyoxal on the LPP1-encoded enzyme were novel properties when compared with other Mg(2+)-independent lipid phosphate phosphatases from S. cerevisiae and mammalian cells. The LPP1-encoded enzyme exhibited saturation kinetics with respect to the surface concentrations of PA (K(m)=0.05 mol%), DGPP (K(m)=0.07 mol%), and LPA (K(m)=0.08 mol%). Based on specificity constants (V(max)/K(m)LPA (1.3 units/mg/mol%). DGPP (K(i)=0.12 mol%) was a competitive inhibitor with respect to PA, and PA (K(i)=0.12 mol%) was a competitive inhibitor with respect to DGPP. This suggested that the binding sites for these substrates were the same. The enzymological properties of the LPP1-encoded enzyme differed significantly from those of the S. cerevisiae DPP1-encoded lipid phosphatase, a related enzyme that also utilizes PA, DGPP, and LPA as substrates. << Less

  Biochim. Biophys. Acta 1484:71-82(2000) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Isolation and characterization of the Saccharomyces cerevisiae LPP1 gene encoding a Mg2+-independent phosphatidate phosphatase.

  Toke D.A., Bennett W.L., Oshiro J., Wu W.I., Voelker D.R., Carman G.M.

  The DPP1-encoded diacylglycerol pyrophosphate (DGPP) phosphatase enzyme accounts for half of the Mg2+-independent phosphatidate (PA) phosphatase activity in Saccharomyces cerevisiae. The LPP1 (lipid phosphate phosphatase) gene encodes a protein that contains a novel phosphatase sequence motif foun ... >> More

  The DPP1-encoded diacylglycerol pyrophosphate (DGPP) phosphatase enzyme accounts for half of the Mg2+-independent phosphatidate (PA) phosphatase activity in Saccharomyces cerevisiae. The LPP1 (lipid phosphate phosphatase) gene encodes a protein that contains a novel phosphatase sequence motif found in DGPP phosphatase and in the mouse Mg2+-independent PA phosphatase. A genomic copy of the S. cerevisiae LPP1 gene was isolated and was used to construct lpp1Delta and lpp1Delta dpp1Delta mutants. A multicopy plasmid containing the LPP1 gene directed a 12.9-fold overexpression of Mg2+-independent PA phosphatase activity in the S. cerevisiae lpp1Delta dpp1Delta double mutant. The heterologous expression of the S. cerevisiae LPP1 gene in Sf-9 insect cells resulted in a 715-fold overexpression of Mg2+-independent PA phosphatase activity relative to control insect cells. The Mg2+-independent PA phosphatase activity encoded by the LPP1 gene was associated with the membrane fraction of the cell. The LPP1 gene product also exhibited lyso-PA phosphatase and DGPP phosphatase activities. The order of substrate preference was PA > lyso-PA > DGPP. Like the dpp1Delta mutant, the lpp1Delta mutant and the lpp1Delta dpp1Delta double mutant were viable and did not exhibit obvious growth defects. Biochemical analyses of lpp1Delta, dpp1Delta, and lpp1Delta dpp1Delta mutants showed that the LPP1 and DPP1 gene products encoded nearly all of the Mg2+-independent PA phosphatase and lyso-PA phosphatase activities and all of the DGPP phosphatase activity in S. cerevisiae. Moreover, the analyses of the mutants showed that the LPP1 and DPP1 gene products played a role in the regulation of phospholipid metabolism and the cellular levels of phosphatidylinositol and PA. << Less

  J. Biol. Chem. 273:14331-14338(1998) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• The Saccharomyces cerevisiae PHM8 gene encodes a soluble magnesium-dependent lysophosphatidic acid phosphatase.

  Reddy V.S., Singh A.K., Rajasekharan R.

  Phosphate is the essential macronutrient required for the growth of all organisms. In Saccharomyces cerevisiae, phosphatases are up-regulated, and the level of lysophosphatidic acid (LPA) is drastically decreased under phosphate-starved conditions. The reduction in the LPA level is attributed to P ... >> More

  Phosphate is the essential macronutrient required for the growth of all organisms. In Saccharomyces cerevisiae, phosphatases are up-regulated, and the level of lysophosphatidic acid (LPA) is drastically decreased under phosphate-starved conditions. The reduction in the LPA level is attributed to PHM8, a gene of unknown function. phm8Delta yeast showed a decreased LPA-hydrolyzing activity under phosphate-limiting conditions. Overexpression of PHM8 in yeast resulted in an increase in the LPA phosphatase activity in vivo. In vitro assays of the purified recombinant Phm8p revealed magnesium-dependent LPA phosphatase activity, with maximal activity at pH 6.5. The purified Phm8p did not hydrolyze any lipid phosphates other than LPA. In silico analysis suggest that Phm8p is a soluble protein with no transmembrane domain. Site-directed mutational studies revealed that aspartate residues in a DXDXT motif are important for the catalysis. These findings indicated that LPA plays a direct role in phosphate starvation. This is the first report of the identification and characterization of magnesium-dependent soluble LPA phosphatase. << Less

  J Biol Chem 283:8846-8854(2008) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.