Publications

• Structural features of GPI-specific phospholipase D revealed by proteolytic fragmentation and Ca2+ binding studies.

  Li J.Y., Hollfelder K., Huang K.S., Low M.G.

  Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) is abundant in plasma and is potentially capable of degrading the anchor utilized by many cell surface proteins. The goal of this work was to study structural features of the GPI-PLD that might be involved in regulation of its activit ... >> More

  Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) is abundant in plasma and is potentially capable of degrading the anchor utilized by many cell surface proteins. The goal of this work was to study structural features of the GPI-PLD that might be involved in regulation of its activity. Trypsin cleaved the 100-110 kDa GPI-PLD polypeptide into three major fragments (two of approximately 40 kDa and a carboxyl-terminal fragment of 30 kDa) which were relatively resistant to further proteolysis. Pretreatment of the GPI-PLD with chelators resulted in complete degradation. During the cleavage process the GPI-PLD enzymatic activity increased approximately 3-4-fold but no other major change in its properties (e.g. inhibition by chelators and lipids, thermal stability, oligomerization, etc.) was observed. Intact or trypsinized GPI-PLD bound 45Ca2+ (approximately 5.5 ions/molecule GPI-PLD; Kd approximately 16.1 microM as determined by equilibrium dialysis) which could not be blocked by the addition of other divalent metal ions. However, inhibition of enzymatic activity by divalent cation chelators appeared to involve removal of bound Zn2+ rather than Ca2+. A metal analysis of GPI-PLD revealed approximately 5 and 10 atom/molecule of calcium and zinc, respectively. The data suggest that the predicted integrin E-F hand-like sites in GPI-PLD are functional but not directly involved in enzymatic activity. << Less

  J Biol Chem 269:28963-28971(1994) [PubMed] [EuropePMC]

• GPI-specific phospholipase D associates with an apoA-I- and apoA-IV-containing complex.

  Deeg M.A., Bierman E.L., Cheung M.C.

  Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) is abundant in serum and associates with high density lipoproteins (HDL). We have characterized the distribution of GPI-PLD among lipoproteins in human plasma. Apolipoprotein (apo)-specific lipoproteins containing apoB (Lp[B]), apoA-I ... >> More

  Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) is abundant in serum and associates with high density lipoproteins (HDL). We have characterized the distribution of GPI-PLD among lipoproteins in human plasma. Apolipoprotein (apo)-specific lipoproteins containing apoB (Lp[B]), apoA-I and A-II (Lp[A-I, A-II]), or apoA-I only (Lp[A-I]) were isolated using dextran sulfate and immunoaffinity chromatography. In six human plasma samples with HDL cholesterol ranging from 39 to 129 mg/dl, 79 +/- 14% (mean +/-SD) of the total plasma GPI-PLD activity was associated with Lp[A-I], 9 +/-12% with Lp[A-I, A-II], and 1 +/- 1% with Lp[B]; and 11 +/-10% was present in plasma devoid of these lipoproteins. Further characterization of the GPI-PLD-containing lipoproteins by gel-filtration chromatography and nondenaturing polyacrylamide and agarose gel electrophoresis revealed that these apoA-I-containing particles/complexes were small (8 nm) and migrated with pre-beta particles on agarose electrophoresis. Immunoprecipitation of GPI-PLD with a monoclonal antibody to GPI-PLD co-precipitated apoA-I and apoA-IV but little or no apoA-II, apoC-II, apoC-III, apoD, or apoE. In vitro, apoA-I but not apoA-IV or bovine serum albumin interacted directly with GPI-PLD, but did not stimulate GPI-PLD-mediated cleavage of a cell surface GPI-anchored protein. Thus, the majority of plasma GPI-PLD appears to be specifically associated with a small, discrete, and minor fraction of lipoproteins containing apoA-I and apoA-IV. --Deeg, M. A., E. L. Bierman, and M. C. Cheung. GPI-specific phospholipase D associates with an apoA-I- and apoA-IV-containing complex. J. Lipid Res. 2001. 42: 442--451. << Less

  J Lipid Res 42:442-451(2001) [PubMed] [EuropePMC]

• A phospholipase D specific for the phosphatidylinositol anchor of cell-surface proteins is abundant in plasma.

  Low M.G., Prasad A.R.

  An enzyme activity capable of degrading the glycosyl-phosphatidylinositol membrane anchor of cell-surface proteins has previously been reported in a number of mammalian tissues. The experiments reported here demonstrate that this anchor-degrading activity is also abundant in mammalian plasma. The ... >> More

  An enzyme activity capable of degrading the glycosyl-phosphatidylinositol membrane anchor of cell-surface proteins has previously been reported in a number of mammalian tissues. The experiments reported here demonstrate that this anchor-degrading activity is also abundant in mammalian plasma. The activity was inhibited by EGTA or 1,10-phenanthroline. It was capable of removing the anchor from alkaline phosphatase, 5'-nucleotidase, and variant surface glycoprotein but had little or not activity toward phosphatidylinositol or phosphatidylcholine. Phosphatidic acid was the only 3H-labeled product when this enzyme hydrolyzed [3H]myristate-labeled variant surface glycoprotein. It could be distinguished from the Ca2+-dependent inositol phospholipid-specific phospholipase C activity in several rat tissues on the basis of its molecular size and its sensitivity to 1,10-phenanthroline. The data therefore suggest that this activity is due to a phospholipase D with specificity for glycosyl-phosphatidylinositol structures. Although the precise physiological function of this anchor-specific phospholipase D remains to be determined, these findings indicate that it could play an important role in regulating the expression and release of cell-surface proteins in vivo. << Less

  Proc Natl Acad Sci U S A 85:980-984(1988) [PubMed] [EuropePMC]