Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.31 (beta-glucuronidase)
 7,680 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The transverse distribution of enzyme proteins and phospholipids within microsomal membranes was studied by analyzing membrane composition after treatment with proteases and phospholipases. Upon trypsin treatment of closed microsomal vesicles, NADH- and NADPH-cytochrome c reductases as well as cytochrome b5 were solubilized or inactivated, while cytochrome P-450 was partially inactivated. When microsomes were exposed to a concentration of deoxycholate which makes them permeable to macromolecules but does not disrupt the membrane, the detergent alone was sufficient to release four enzymes: nucleoside diphosphatase, esterase, beta-glucuronidase, and a portion of the DT-diaphorase. Introduction of trypsin into the vesicle lumen inactivated glucose-6-phosphatase completely and cytochrome P-450 partially. The rest of this cytochrome, ATPase, AMPase, UDP-glucuronyltransferase, and the remaining 50% of DT-diaphorase activity were not affected by proteolysis from either side of the membrane. Phospholipase A treatment of intact microsomes in the presence of albumin hydrolyzed all of the phosphatidylethanolamine, phosphatidylserine, and 55% of the phosphatidylcholine. From this observation, it was concluded that these lipids are localized in the outer half of the bilayer of the microsomal membrane; Phosphatidylinositol, 45% of the phosphatidylcholine, and sphingomyelin are tentatively assigned to the inner half of this bilayer. It appears that the various enzyme proteins and phospholipids of the microsomal membrane display an asymmetric distribution in the transverse plane.
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PMID:Enzyme and phospholipid asymmetry in liver microsomal membranes. 19 Feb 41

We have studied the phospholipase A2 activity in fractionated human neutrophils, employing labeled phosphatidylinositol, phosphatidylcholine, and phosphatidylethanolamine as exogenous substrates. We used these phospholipid substrates labeled in the sn-1 position and measured the resulting labeled lysophospholipid forms in order to ascertain the phospholipase A2 specificity. In postnuclear supernatants from resting and A23187-activated cells, the phospholipase A2 activity showed a similar pH dependence curve with two pH optima at 5.5 and 7.5. Extracts from activated cells showed a 3-6-fold increase in enzyme activity. The subcellular distribution of phospholipase A2 activity in resting and A23187-treated human neutrophils was investigated by fractionation of postnuclear supernatants on continuous sucrose gradients. The neutral phospholipase A2 behaved as a membrane-bound enzyme and was mainly localized in the plasma membrane, the azurophilic granule, and in an ill-defined region of the gradient between the specific granules and mitochondria. The phospholipase A2 located in this undefined region showed a higher degree of activation than that located in other subcellular particulates in A23187-treated cells. This specific activation of an intracellular phospholipase A2 activity during cell stimulation indicates that cell compartmentalization may play a role in the formation of cell-activating and/or signal-transducing agents through the generation of arachidonate metabolites. Phosphatidylinositol was a better substrate for the plasma membrane enzyme, whereas phosphatidylcholine and phosphatidylethanolamine behaved as better substrates for intracellular organelle phospholipase A2 activities. The phospholipase A2 with maximal activity at pH 5.5 behaved as a soluble enzyme, and was almost completely localized in the azurophilic granules. Upon cell activation this acid enzyme activity was released in a similar way to beta-glucuronidase, a marker of azurophilic granules. These results demonstrate the different molecular properties of the phospholipase A2 activity, on the basis of its cellular location.
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PMID:Phospholipase A2 activity in resting and activated human neutrophils. Substrate specificity, pH dependence, and subcellular localization. 312 82

1-O-Alkyl-2-O-acetyl-sn-glycero-3-phosphocholine (AAGPC) triggered the release of [3H]arachidonate but not [14C]stearate from cellular phospholipids in cytochalasin B-treated rabbit polymorphonuclear leukocytes. Concentrations of AAGPC up to 20 nM caused a dose-dependent release and subsequent metabolism of the released [3H]arachidonic acid. Most of the release of the [3H]arachidonate had taken place within the first 2 min of stimulation. Phosphatidylinositol and phosphatidylcholine served as the sources of [3H]arachidonate with about 50% of the label coming from each pool. Challenge of cytochalasin B-treated polymorphonuclear leukocytes with AAPGC led to the production of [3H]hydroxyeicosatetraenoic acids and [3H]dihydroxyeicosatetraenoic acids. No significant production of [3H]prostaglandins or [3H]thromboxanes was detected. AAGPC also caused a dose-dependent degranulation of cytochalasin B-treated rabbit polymorphonuclear leukocytes as shown by the release of beta-glucuronidase and lysozyme. Both the AAGPC-stimulated production of arachidonate metabolites and the degranulation response were blocked by eicosatetraynoic acid and non-dihydroguaiaretic acid at similar inhibitor concentrations. These findings suggest the bioactions of AAGPC on polymorphonuclear leukocytes may be mediated by the release of arachidonic acid and the production of mono- and dihydroxyeicosatetraenoic acids.
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PMID:Platelet activating factor. Stimulation of the lipoxygenase pathway in polymorphonuclear leukocytes by 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine. 680 16

Phosphatidylinositol signaling pathway and the relevant metabolites are known to be critical to the modulation of different aspects of plant growth, development, and stress responses. Inositol polyphosphate 5-phosphatase is a key enzyme involved in phosphatidylinositol metabolism and is encoded by an At5PTase gene family in Arabidopsis thaliana. A previous study shows that At5PTase11 mediates cotyledon vascular development probably through the regulation of intracellular calcium levels. In this study, we provide evidence that At5PTase13 modulates the development of cotyledon veins through its regulation of auxin homeostasis. A T-DNA insertional knockout mutant, At5pt13-1, showed a defect in development of the cotyledon vein, which was rescued completely by exogenous auxin and in part by brassinolide, a steroid hormone. Furthermore, the mutant had reduced auxin content and altered auxin accumulation in seedlings revealed by the DR5:beta-glucuronidase fusion construct in seedlings. In addition, microarray analysis shows that the transcription of key genes responsible for auxin biosynthesis and transport was altered in At5pt13-1. The At5pt13-1 mutant was also less sensitive to auxin inhibition of root elongation. These results suggest that At5PTase13 regulates the homeostasis of auxin, a key hormone controlling vascular development in plants.
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PMID:At5PTase13 modulates cotyledon vein development through regulating auxin homeostasis. 1629 82