The Escherichia coli pgpB Gene Encodes for a Diacylglycerol Pyrophosphate Phosphatase Activity

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211

We obtained two human cDNA clones encoding phosphatidic acid phosphatase (PAP) isozymes named PAP-2a (M r ‫؍‬ 32,158) and -2b (M r ‫؍‬ 35, 119), both of which contained six putative transmembrane domains. Both enzymes were glycosylated and cleaved by N-glycanase and endo-␤-galactosidase, thus suggesting their post-Golgi localization. PAP-2a and -2b shared 47% identical sequence and were judged to be the human counterparts of the previously sequenced mouse 35-kDa PAP(83% identity) and rat Dri42 protein (94% identity), respectively. Furthermore, the sequences of both PAPs were 34 -39% identical to that of Drosophila Wunen protein. In view of the functions ascribed to Wunen and Dri42 in germ cell migration and epithelial differentiation, respectively, these findings unexpectedly suggest critical roles of PAP isoforms in cell growth and differentiation. Although the two PAPs hydrolyzed lysophosphatidate and ceramide-1-phosphate in addition to phosphatidate, the hydrolysis of sphingosine-1-phosphate was detected only for PAP-2b. PAP-2b was expressed almost ubiquitously in all human tissues examined, whereas the expression of PAP-2a was relatively variable, being extremely low in the placenta and thymus. In HeLa cells, the transcription of PAP-2a was not affected by different stimuli, whereas PAP-2b was induced (up to 3-fold) by epidermal growth factor. These findings indicate that despite structural similarities, the two PAP isozymes may play distinct functions through their different patterns of substrate utilization and transcriptional regulation.Phosphatidic acid phosphatase (PAP) 1 (EC 3.1.3.4) supplies diacylglycerol (DG) in glycerolipid biosynthesis by dephosphorylating phosphatidic acid (PA) (1). Since both DG (2) and PA (3) are potent signaling molecules, PAP plays an important role in cellular signal transduction in addition to lipid biosynthesis (4). In signaling systems mediated by phospholipase D (5), liberated PA is generally converted, albeit to different extents, to DG by the action of PAP (6 -8), thus suggesting that PAP contributes to the control of the relative balance of the two lipid second messengers.There exist two forms of mammalian PAP that can be distinguished with respect to subcellular localization and enzymologic properties (9). So far, distinct functions have been ascribed to the two forms of PAP. The type 1 PAP, a Mg 2ϩ -dependent and N-ethylmaleimide-sensitive enzyme, is considered to be primarily involved in lipid synthesis based on its translocation from the cytosol to microsomes upon stimulation of cellular triacylglycerol synthesis (10 -12). In this context, a recent work showed using a novel enzyme inhibitor that the type 1 PAP indeed participated in triacylglycerol synthesis in mouse macrophages (13). On the other hand, the type 2 PAP, a Mg 2ϩ -independent and N-ethylmaleimide-insensitive enzyme, has been postulated to participate in cellular signal transduction mediated by phospholipase D. The finding that the activities of the type 2 PAP and phospholipase D were decreased in a c...

Section: B Lane 5)mentioning

confidence: 99%

Cloning and Characterization of Two Human Isozymes of Mg2+-independent Phosphatidic Acid Phosphatase

Kai

Wada

Imai

et al. 1997

175

211

“…Since ATP would not be available in the outer parts of the envelope, other donors of high energy phosphate moieties must be considered, such as bactoprenol-pyrophosphate, a product of O-antigen polymerization ( Fig. 1) (4), or diacylglycerol-pyrophosphate, a newly discovered, minor lipid (46). Attempts to generate trisphosphate in vitro using ATP and Kdo 2 -lipid IV A have been unsuccessful.…”

Section: Fig 12mentioning

confidence: 99%

Function of Escherichia coli MsbA, an Essential ABC Family Transporter, in Lipid A and Phospholipid Biosynthesis

Zhou¹,

White²,

Polissi³

et al. 1998

326

339

“…Conserved Arg 125 , His 169 , and His 223 residues within domains 1, 2, and 3, respectively, play important roles in the phosphatase reactions catalyzed by the enzyme (20). The DGPP phosphatase enzyme also utilizes lysophosphatidate (15), sphingolipid phosphates (21), and isoprenoid phosphates (22) as substrates in vitro. However, only DGPP and PA have been shown to be substrates in vivo (1).…”

mentioning

confidence: 99%

“…The DGPP phosphatase protein (1) contains a three-domain phosphatase sequence motif (12-14) that is conserved in a superfamily of lipid phosphatase enzymes (15)(16)(17)(18)(19) We have begun to examine the regulation of DGPP phosphatase expression in S. cerevisiae to gain an understanding of DGPP function. The enzyme is induced by inositol in both exponential and stationary phase cells (23).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Regulation of the Saccharomyces cerevisiae DPP1-encoded Diacylglycerol Pyrophosphate Phosphatase by Zinc

Han

Johnston

Chen

et al. 2001

Self Cite

The DPP1 gene, encoding diacylglycerol pyrophosphate (DGPP) phosphatase from Saccharomyces cerevisiae, has recently been identified as a zinc-regulated gene, and it contains a putative zinc-responsive element (UAS ZRE ) in its promoter. In this work we examined the hypothesis that expression of DGPP phosphatase was regulated by zinc availability. The deprivation of zinc from the growth medium resulted in a time-and dosedependent induction of ␤-galactosidase activity driven by a P DPP1 -lacZ reporter gene. This regulation was dependent on the UAS ZRE in the DPP1 promoter and was mediated by the Zap1p transcriptional activator. Induction of the DGPP phosphatase protein and activity by zinc deprivation was demonstrated by immunoblot analysis and measurement of the dephosphorylation of DGPP. The regulation pattern of DGPP phosphatase in mutants defective in plasma membrane (Zrt1p and Zrt2p) and vacuolar membrane (Zrt3p) zinc transporters indicated that enzyme expression was sensitive to the cytoplasmic levels of zinc. DGPP phosphatase activity was inhibited by zinc by a mechanism that involved formation of DGPP-zinc complexes. Studies with well characterized subcellular fractions and by indirect immunofluorescence microscopy revealed that the DGPP phosphatase enzyme was localized to the vacuolar membrane.The DPP1-encoded diacylglycerol pyrophosphate (DGPP) 1 phosphatase (1) is a membrane-associated enzyme from the yeast Saccharomyces cerevisiae that catalyzes the removal of the ␤-phosphate from DGPP to form PA and then removes the phosphate from PA to form DG (2). DGPP is a minor phospholipid in S. cerevisiae (2) that contains a pyrophosphate group attached to DG (3). DGPP is derived from PA via the reaction catalyzed by PA kinase (2, 4). DGPP is postulated to function in a novel lipid-signaling pathway (5, 6). Metabolic labeling studies with plants, where DGPP was first discovered (3), show that DGPP accumulates upon G protein activation (7) and upon hyperosmotic stress (8, 9). Exogenous DGPP augments secretion of prostaglandins in mouse macrophages (10). This occurs by a mechanism that involves the activation of cytosolic phospholipase A 2 via the mitogen-activated protein kinase pathway, an important event in the immunoinflammatory response of leukocytes (10). The accumulation of DGPP in plants is short-lived (9); it is rapidly converted to PA and then to DG (11), consistent with the reactions catalyzed by yeast DGPP phosphatase (2).DPP1-encoded DGPP phosphatase also exhibits a PA phosphatase activity (2), but DGPP is the preferred substrate, with a specificity constant 10-fold higher than that of PA (2). The DGPP phosphatase protein (1) contains a three-domain phosphatase sequence motif (12-14) that is conserved in a superfamily of lipid phosphatase enzymes (15)(16)(17)(18)(19) We have begun to examine the regulation of DGPP phosphatase expression in S. cerevisiae to gain an understanding of DGPP function. The enzyme is induced by inositol in both exponential and stationary phase cells (23). DGPP phosphatase exp...