Publications

• Phosphatidic acid phosphatase, a key enzyme in the regulation of lipid synthesis.

  Carman G.M., Han G.S.

  J Biol Chem 284:2593-2597(2009) [PubMed] [EuropePMC]

• Mammalian Mg2+-independent phosphatidate phosphatase (PAP2) displays diacylglycerol pyrophosphate phosphatase activity.

  Dillon D.A., Chen X., Zeimetz G.M., Wu W.I., Waggoner D.W., Dewald J., Brindley D.N., Carman G.M.

  Recent studies indicate that the metabolism of diacylglycerol pyrophosphate (DGPP) is involved in a novel lipid signaling pathway. DGPP phosphatases (DGPP phosphohydrolase) from Saccharomyces cerevisiae and Escherichia coli catalyze the dephosphorylation of DGPP to yield phosphatidate (PA) and the ... >> More

  Recent studies indicate that the metabolism of diacylglycerol pyrophosphate (DGPP) is involved in a novel lipid signaling pathway. DGPP phosphatases (DGPP phosphohydrolase) from Saccharomyces cerevisiae and Escherichia coli catalyze the dephosphorylation of DGPP to yield phosphatidate (PA) and then catalyze the dephosphorylation of PA to yield diacylglycerol. We demonstrated that the Mg2+-independent form of PA phosphatase (PA phosphohydrolase, PAP2) purified from rat liver catalyzed the dephosphorylation of DGPP. This reaction was Mg2+-independent, insensitive to inhibition by N-ethylmaleimide and bromoenol lactone, and inhibited by Mn2+ ions. PAP2 exhibited a high affinity for DGPP (Km = 0.04 mol %). The specificity constant (Vmax/Km) for DGPP was 1. 3-fold higher than that of PA. DGPP inhibited the ability of PAP2 to dephosphorylate PA, and PA inhibited the dephosphorylation of DGPP. Like rat liver PAP2, the Mg2+-independent PA phosphatase activity of DGPP phosphatase purified from S. cerevisiae was inhibited by lyso-PA, sphingosine 1-phosphate, and ceramide 1-phosphate. Mouse PAP2 showed homology to DGPP phosphatases from S. cerevisiae and E. coli, especially in localized regions that constitute a novel phosphatase sequence motif. Collectively, our work indicated that rat liver PAP2 is a member of a phosphatase family that includes DGPP phosphatases from S. cerevisiae and E. coli. We propose a model in which the phosphatase activities of rat liver PAP2 and the DGPP phosphatase of S. cerevisiae regulate the cellular levels of DGPP, PA, and diacylglycerol. << Less

  J Biol Chem 272:10361-10366(1997) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• 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.

• Fracture resistance of endodontically prepared teeth using various restorative materials.

  Oliveira F.d.e. C., Denehy G.E., Boyer D.B.

  This study compares the fracture resistance of endodontically treated premolars with modified types of cavity preparations and restoration with either amalgam or composite resin. The greatest influence on fracture resistance was the remaining tooth structure. The effect of adequate wall support on ... >> More

  This study compares the fracture resistance of endodontically treated premolars with modified types of cavity preparations and restoration with either amalgam or composite resin. The greatest influence on fracture resistance was the remaining tooth structure. The effect of adequate wall support on tooth strength was compared with intact unprepared teeth. << Less

  J Am Dent Assoc 115:57-60(1987) [PubMed] [EuropePMC]

• The Saccharomyces cerevisiae Lipin homolog is a Mg2+-dependent phosphatidate phosphatase enzyme.

  Han G.S., Wu W.I., Carman G.M.

  Mg(2+)-dependent phosphatidate (PA) phosphatase (3-sn-phosphatidate phosphohydrolase, EC 3.1.3.4) catalyzes the dephosphorylation of PA to yield diacylglycerol and P(i). In this work, we identified the Saccharomyces cerevisiae PAH1 (previously known as SMP2) gene that encodes Mg(2+)-dependent PA p ... >> More

  Mg(2+)-dependent phosphatidate (PA) phosphatase (3-sn-phosphatidate phosphohydrolase, EC 3.1.3.4) catalyzes the dephosphorylation of PA to yield diacylglycerol and P(i). In this work, we identified the Saccharomyces cerevisiae PAH1 (previously known as SMP2) gene that encodes Mg(2+)-dependent PA phosphatase using amino acid sequence information derived from a purified preparation of the enzyme (Lin, Y.-P., and Carman, G. M. (1989) J. Biol. Chem. 264, 8641-8645). Overexpression of PAH1 in S. cerevisiae directed elevated levels of Mg(2+)-dependent PA phosphatase activity, whereas the pah1Delta mutation caused reduced levels of enzyme activity. Heterologous expression of PAH1 in Escherichia coli confirmed that Pah1p is a Mg(2+)-dependent PA phosphatase enzyme and showed that its enzymological properties were very similar to those of the enzyme purified from S. cerevisiae. The PAH1-encoded enzyme activity was associated with both the membrane and cytosolic fractions of the cell, and the membrane-bound form of the enzyme was salt-extractable. Lipid analysis showed that mutants lacking PAH1 accumulated PA and had reduced amounts of diacylglycerol and its derivative triacylglycerol.ThePAH1-encoded Mg(2+)-dependent PA phosphatase shows homology to mammalian lipin, a fat-regulating protein whose molecular function is unknown. Heterologous expression of human LPIN1 in E. coli showed that lipin 1 is also a Mg(2+)-dependent PA phosphatase enzyme. << Less

  J. Biol. Chem. 281:9210-9218(2006) [PubMed] [EuropePMC]

• Purification and characterization of diacylglycerol pyrophosphate phosphatase from Saccharomyces cerevisiae.

  Wu W.-I., Liu Y., Riedel B., Wissing J.B., Fischl A.S., Carman G.M.

  Diacylglycerol pyrophosphate (DGPP) phosphatase is a novel membrane-associated enzyme that catalyzes the dephosphorylation of the beta phosphate of DGPP to yield phosphatidate and Pi. DGPP phosphatase was purified 33,333-fold from Saccharomyces cerevisiae by a procedure that included Triton X-100 ... >> More

  Diacylglycerol pyrophosphate (DGPP) phosphatase is a novel membrane-associated enzyme that catalyzes the dephosphorylation of the beta phosphate of DGPP to yield phosphatidate and Pi. DGPP phosphatase was purified 33,333-fold from Saccharomyces cerevisiae by a procedure that included Triton X-100 solubilization of microsomal membranes followed by chromatography with DE53, Affi-Gel Blue, hydroxylapatite, and Mono Q. The procedure resulted in the isolation of an apparent homogeneous protein with a subunit molecular mass of 34 kDa. DGPP phosphatase activity was associated with the 34-kDa protein. DGPP phosphatase had a broad pH optimum between 6.0 and 8.5 and was dependent on Triton X-100 for maximum activity. The enzyme was inhibited by divalent cations, NaF, and pyrophosphate and was relatively insensitive to thioreactive agents. The turnover number (molecular activity) for the enzyme was 5.8 x 10(3) min-1 at pH 6.5 and 30 degrees C. DGPP phosphatase exhibited typical saturation kinetics with respect to DGPP (Km = 0.55 mol %). The Km value for DGPP was 3-fold greater than its cellular concentration (0.18 mol %). DGPP phosphatase also catalyzed the dephosphorylation of phosphatidate, but this dephosphorylation was subsequent to the dephosphorylation of the beta phosphate of DGPP. The dependence of activity on phosphatidate (Km = 2.2 mol %) was cooperative (Hill number = 2.0). DGPP was the preferred substrate for the enzyme with a specificity constant (Vmax/Km) 10-fold greater than that for phosphatidate. In addition, DGPP potently inhibited (Ki = 0.35 mol %) the dephosphorylation of phosphatidate by a competitive mechanism whereas phosphatidate did not inhibit the dephosphorylation of DGPP. DGPP was neither a substrate nor an inhibitor of pure phosphatidate phosphatase from S. cerevisiae. DGPP was synthesized from phosphatidate via the phosphatidate kinase reaction. << Less

  J. Biol. Chem. 271:1868-1876(1996) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Lipid phosphate phosphohydrolase-1 degrades exogenous glycerolipid and sphingolipid phosphate esters.

  Jasinska R., Zhang Q.-X., Pilquil C., Singh I., Xu J., Dewald J., Dillon D.A., Berthiaume L.G., Carman G.M., Waggoner D.W., Brindley D.N.

  Lipid phosphate phosphohydrolase (LPP)-1 cDNA was cloned from a rat liver cDNA library. It codes for a 32-kDa protein that shares 87 and 82% amino acid sequence identities with putative products of murine and human LPP-1 cDNAs, respectively. Membrane fractions of rat2 fibroblasts that stably expre ... >> More

  Lipid phosphate phosphohydrolase (LPP)-1 cDNA was cloned from a rat liver cDNA library. It codes for a 32-kDa protein that shares 87 and 82% amino acid sequence identities with putative products of murine and human LPP-1 cDNAs, respectively. Membrane fractions of rat2 fibroblasts that stably expressed mouse or rat LPP-1 exhibited 3.1-3. 6-fold higher specific activities for phosphatidate dephosphorylation compared with vector controls. Increases in the dephosphorylation of lysophosphatidate, ceramide 1-phosphate, sphingosine 1-phosphate and diacylglycerol pyrophosphate were similar to those for phosphatidate. Rat2 fibroblasts expressing mouse LPP-1 cDNA showed 1.6-2.3-fold increases in the hydrolysis of exogenous lysophosphatidate, phosphatidate and ceramide 1-phosphate compared with vector control cells. Recombinant LPP-1 was located partially in plasma membranes with its C-terminus on the cytosolic surface. Lysophosphatidate dephosphorylation was inhibited by extracellular Ca2+ and this inhibition was diminished by extracellular Mg2+. Changing intracellular Ca2+ concentrations did not alter exogenous lysophosphatidate dephosphorylation significantly. Permeabilized fibroblasts showed relatively little latency for the dephosphorylation of exogenous lysophosphatidate. LPP-1 expression decreased the activation of mitogen-activated protein kinase and DNA synthesis by exogenous lysophosphatidate. The product of LPP-1 cDNA is concluded to act partly to degrade exogenous lysophosphatidate and thereby regulate its effects on cell signalling. << Less

  Biochem. J. 340:677-686(1999) [PubMed] [EuropePMC]

  This publication is cited by 8 other entries.