Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A set of radioiodinatable phosphatidylcholines (PCs) derivatized with the Bolton-Hunter reagent (BHPCs) was synthesized to probe the substrate recognition and activity of phospholipases. A common feature of this series is the presence of a bulky 4-hydroxyphenyl group at the end of the fatty acyl chain attached to position sn-2. The distance between the end group and the glycerol backbone was varied by changing the length of the intervening fatty acyl chain (3-25 atoms). Except for the shortest, this chain includes at least one amide linkage. The usefulness of this series of substrates as a molecular ruler was tested by measuring the hydrolytic activities of Naja naja naja phospholipase A(2) (PLA(2)) and Bacillus cereus phospholipase C (PLC) in Triton X-100 micelles. The activity of PLA(2) proved to be highly dependent on the length of the fatty acyl chain linker, the shorter compounds (3-10 atoms) being very poor substrates. In contrast, the PLC activity profile exhibited much less discrimination. In both cases, PCs with 16-21 atom chains at position sn-2 yielded optimal activity. We interpret these findings in terms of fatty acyl chain length-related steric hindrance caused by the terminal aromatic group, affecting the activity of PLA(2) and, to a smaller extent, that of PLC. This notion agrees with the more extended recognition of aliphatic chains inside the narrow channel leading to the catalytic site in the former case. Molecular models of these substrates bound to PLA(2) were built on the basis of the crystallographic structure of Naja naja atra PLA(2) complexed with a phospholipid analogue. Docking of these substrates necessarily requires the intrusion of the bulky 4-hydroxyphenyl group inside the binding pocket and also the failure of the amide group to form hydrogen bonds inside the hydrophobic substrate channel.
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PMID:Mapping the catalytic pocket of phospholipases A2 and C using a novel set of phosphatidylcholines. 1069 94

The signal transduction involved in the purinergic stimuli-induced activation of protein kinase C (PKC) in CHO-K1 cells was investigated. Purinergic stimuli such as adenosine triphosphate and uridine triphosphate induced a transient translocation of PKC epsilon, gamma, and delta from the cytoplasm to the plasma membrane. These translocations were blocked by an inhibitor of phosphatidylinositol-specific phospholipase C (PLC), but not by an inhibitor of phosphatidylcholine-specific PLC. A diacylglycerol (DAG) analogue also induced reversible translocations of PKC gamma, epsilon, and delta from the cytoplasm to the plasma membrane, while the calcium ionophore A23187 caused a similar translocation of only the gamma subtype. These results confirm that the hydrolysis of phosphatidylinositol-2-phosphate by PLC and the subsequent generation of DAG and increase in Ca(2+ )are involved in the purinergic stimuli-induced translocation of PKC. A DAG antagonist, 1-o-hexadecyl-2-o-acetyl-glycerol, blocked the DAG analogue-induced translocations of all PKC subtypes tested but failed to inhibit the purinergic stimuli-induced translocations of PKC epsilon and gamma. The DAG antagonist could not block the ATP- and UTP-induced translocation of PKC epsilon even in the absence of extracellular Ca(2+). Co-application of the DAG antagonist and a phospholipase A(2) (PLA(2)) inhibitor such as aristolochic acid, arachidonyltrifluoromethyl ketone, or bromoenol lactone inhibited the purinergic receptor-mediated translocation of PKC epsilon although each PLA(2) inhibitor alone did not block the translocation. In contrast to the epsilon subtype, ATP-induced translocation of PKC gamma was observed in the presence of both the PLA(2) inhibitor and the DAG antagonist. However, it is noteworthy that re-translocation of PKC gamma was hastened by the PLA(2) inhibitor. Furthermore products of PLA(2), such as lysophospholipids and fatty acids, induced the translocation of PKC gamma and epsilon in a dose dependent manner, but not delta. These results indicate that, in addition to PLC and DAG, PLA(2) and its products are involved in the purinergic stimuli-induced translocation of PKC epsilon and gamma in CHO-K1 cells. Each subtype of PKC in CHO-K1 cell is individually activated in response to a purinergic stimulation.
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PMID:Phospholipase A(2) and its products are involved in the purinergic receptor-mediated translocation of protein kinase C in CHO-K1 cells. 1072 17

Several lines of evidence indicate that phospholipase A(2) (PLA(2)) plays a crucial role in plant cellular responses through production of linolenic acid, the precursor of jasmonic acid, from membrane phospholipids. Here we report the purification and characterization of a 48-kD PLA(2) from the membrane fractions of leaves of broad bean (Vicia faba). The plant PLA(2) was purified to near homogeneity by sequential column chromatographies from the membrane extracts. The purified 48-kD protein migrated as a single band on a SDS-PAGE gel and its density correlated with the PLA(2) activity. It was further confirmed that this 48-kD protein is the PLA(2) enzyme based on immunoprecipitating the activity with a monoclonal antibody against it and purifying the enzyme to homogeneity with the antibody affinity column. The purified plant PLA(2) preferred 2-linolenoyl-sn-glycerol-3-phosphocholine (GPC) to 2-linoleoyl-GPC, 2-palmitoyl-GPC and 2-arachidonyl-GPC as substrates with a pH optimum at pH 7.0 to 8.0. The plant PLA(2) was activated by calmodulin and inhibited by pretreatment of 5,8,11, 14-eicosatetraynoic acid known as an inhibitor of mammalian PLA(2)s. The enzyme was characterized as a Ca(2+)-independent PLA(2) different from mammalian PLA(2)s. This membrane-associated and Ca(2+)-independent PLA(2) is suggested to play an important role in the release of linolenic acid, the precursor of jasmonic acid, through a signal transduction pathway.
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PMID:Purification and characterization of a membrane-associated 48-kilodalton phospholipase A(2) in leaves of broad bean. 1088 55

Fermentation studies of batch-mode cultivation in 4-L fermenters were carried out to obtain an active recombinant DNA-derived tissue plasminogen activator (t-PA) deletion mutant, lekteplase, secreted and correctly folded from Escherichia coli. The OmpA signal sequence was used to deliver the heterologous product composed of kringle 2 plus serine protease domain (K2S) to the medium. Supplementing the complex medium with 10% glycerol and 20 mmol/l magnesium chloride led to an increase in cell numbers with final cell density reaching an OD600 of 24. The expression level of lekteplase in the medium detected by sandwich ELISA was 100 mg/L. Enzymatic activity of lysine-sepharose purified product was demonstrated by amidolytic assay, in vitro fibrin clot lysis, and copolymerization PAGE.
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PMID:Lekteplase--a secreted tissue plasminogen activator derivative from Escherichia coli. 1183 75

Novel carbohydrate-based phospholipids containing two saturated C(12) (dilauroyl ribo-phosphocholine) (DLRPC), C(14) (dimyristoyl ribo-phosphocholine) (DMRPC), and C(20) (diarachadonyl ribo-phosphocholine) (DARPC) carboxylic acid chains were synthesized. The physical properties of the supramolecular structures formed by these compounds were compared to those formed by their direct glycerol analogues dilauroyl phosphocholine (DLPC), dimyristoyl phosphocholine (DMPC), and diarachadonyl phosphocholine (DAPC). Modulated differential scanning calorimetry (MDSC) and X-ray diffraction data indicated that with chain lengths < or =14 carbons, the carbohydrate backbone increased the thermal stability of the bilayer below the phase-transition temperature (T(m)) as compared to the glycerol-based lipids. With longer chains (C(20)), the bilayer structure was destabilized as compared to glycerol-based lipids. NMR studies of a DMRPC vesicle dispersion reveal split choline headgroup signals and distinct magnetization transfer effects arising from the "inner" and "outer" surfaces of the bilayer vesicle. Modulated differential scanning calorimetry also demonstrated that glycerol- and carbohydrate-based lipids mix, as evidenced by a single intermediate T(m). In addition, carbohydrate-based lipid/cholesterol mixtures exhibited a decrease in enthalpy with an increase in cholesterol concentration. Unlike glycerol phospholipids, carbohydrate lipids were resistant to enzymatic degradation by phospholipase A(2) (PLA(2)).
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PMID:Synthesis and characterization of carbohydrate-based phospholipids. 1202 31

The controlled drug delivery of hydrophilic and lipophilic drug substances via the parenteral route has gained increasing importance in the development of pharmaceutical dosage forms. In particular, the animal health industry has generated strong interest in long-term drug delivery for both companion and farm animals during the past few years. At present sustained-release injectables formed in situ for s.c./i.m. administration have become an attractive alternative to common slow release technologies such as microspheres or standard implants. In this context, technologies based on PLA/PLGA, sucrose acetate isobutyrate (SAIB) and the amphipathic molecules Poloxamer, glycerol monooleate or PEG-PLA-PEG copolymers, are discussed. Release periods from hours to months can be obtained by choosing one of these drug delivery technologies. The release times are strongly dependent on the biodegradation of the polymers and the physico-chemical properties of the drug substance used. Furthermore, the use of different solvents for the matrix-forming agents and the individual loading capacity are critically assessed. Additionally acceptance of the excipients for parenteral use by the regulatory authorities is closely considered. Scientific articles as well as patent publications are reviewed to give a wide overview of the existing approaches and their future potential for animal health products.
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PMID:Sustained-release injectables formed in situ and their potential use for veterinary products. 1248 Mar 6

Stimulated production of reactive oxygen species (ROS) by plasma membrane-associated nicotinamide adenine dinucleotide phosphate oxidases (Nox) in non-phagocytic cells regulates a number of biological processes including growth, vessel tone, and oxygen sensing. The purpose of this study was to investigate H(2)O(2)-stimulated ROS production in primary adult cardiac fibroblasts (CF). Results demonstrate that CF express an H(2)O(2)-inducible oxidant generating system that is inhibitable by diphenylene iodonium (DPI) and sensitive to antioxidants. In addition to H(2)O(2), generation of ROS was stimulated potently by 1-oleoyl-2-acetyl-sn-glycerol (OAG) and arachidonic acid (AA) in a protein kinase C-independent manner. Pretreatment with arachidonyl trifluoromethyl ketone was nearly as effective as DPI at reducing H(2)O(2)- and OAG-stimulated oxidant generation indicating a central role for phospholipase A(2) (PLA(2)) in this signaling pathway. Co-stimulation with H(2)O(2) and OAG did not increase ROS generation as compared to OAG alone suggesting both agonists signal through a shared, rate-limited enzymatic pathway involving PLA(2). Co-stimulation with H(2)O(2) and AA had additive effects indicating these two agonists stimulate oxidant production through a parallel activation pathway. Reverse transcriptase-coupled polymerase chain reaction and Western blotting demonstrate primary cardiac fibroblasts express transcripts and protein for Nox4, p22, p47, and p67 phox. Transfections with Nox4 small inhibitory ribonucleic acid oligonucleotides or p22 phox antisense oligonucleotides significantly downregulated stimulated Nox activity. Inhibitors of nitric oxide synthases were without effect. We conclude adult CF express Nox4/p22 phox-containing oxidant generating complex activated by H(2)O(2), OAG, and AA through a pathway that requires activation of PLA(2).
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PMID:H2O2 activates Nox4 through PLA2-dependent arachidonic acid production in adult cardiac fibroblasts. 1584

(R)-Glycerol-monolinoleate 4 and (R)-glycerol-monostearate 5 were isolated from the ethyl acetate extracts of Saururus chinensis roots and (R)- or (S)-fatty acid glycerols 4 and 5 were synthesized for confirming their structures and evaluating their inhibitory activities against Lp-PLA(2). The (R)-4 and (S)-4 exhibited Lp-PLA(2) inhibitory activities with IC(50) values of 45.0 and 52.0 microM, respectively.
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PMID:Lp-PLA2 inhibitory activities of fatty acid glycerols isolated from Saururus chinensis roots. 1596 10

Reliable data on plasmin activities in blood of patients during fibrinolytic treatment are lacking. This is due to continuing plasminogen activation by plasminogen activators after blood withdrawal. The purpose of this study was to establish a new method for stabilization of blood and to detect plasmin activity in stabilized plasma. For optimization of plasma stabilization by arginine, 50 microL pooled normal citrated plasma was incubated with 50 microL of 0 to 1500 mM arginine, pH 8.7, and 25 microL 100 IU/mL u-PA, 1250 IU/mL t-PA, 10000 U/mL reteplase, 400 U/mL plasminogen-streptokinase-activator complex, 10 microg/mL tenecteplase in 6% BSA-PBS or 25 microL 25 microg/mL plasmin in 20% glycerol. Twenty-five microliters 3 mM HD-Val-Leu-Lys-pNA were added immediately (1 step) or after 90 minutes (room temperature [RT]). The same experiment was performed with pooled normal citrated plasma supplemented with 3.2 mg/mL EDTA, preoxidized with 0 mM or 20 mM chloramine-T for 10 minutes (37 degrees C). For optimization of plasmin activity, the oxidation time of the arginine-stabilized plasma sample containing 0.5 U/mL active plasmin and the chloramine-T amount was varied. Citrated plasma is stabilized against the in vitro action of all six plasminogen activators tested if the final arginine concentration is greater than 500 mM. Neither the addition of EDTA nor the addition of chloramine-T changes this plasma-stabilizing power of arginine. The optimized functional plasmin assay consists of incubation of 10 microL arginine-stabilized plasma with 10 microL 1.5 M arginine, pH 8.7, and 10 microL 100 mM CT in PBS. After 30 minutes (37 degrees C), 75 microL 1.2 M KCl, 1.6 M Arg, 0.75 mM Val-Leu-Lys-pNA (Stop-CS Reagent), and 175 microL 6% BSA-PBS are added and the absorbance increase (DeltaA) at 405 nm is determined. With the present arginine stabilization procedure of plasma and the determination of plasmin activity in arginine-stabilized plasma as described, it is feasible to determine the activity of plasmin in blood of patients receiving fibrinolytic treatment without artefactual in vitro changes in the samples.
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PMID:Functional determination of plasmin in arginine-stabilized plasma. 1601 16

We have undertaken a study to characterize the lipolytic pathway responsible for the generation of free fatty acids (FFA) during Fas/CD95-induced apoptosis in Jurkat cells. It was initially shown that the cellular lipid fraction that suffered the major quantitative decrease during Fas-induced apoptosis was that of phosphatidylcholine (PC). In addition, the secretion of palmitic acid-derived FFA was largely prevented by D609, an inhibitor of PC-specific phospholipase C (PC-PLC) and also by the diacylglycerol lipase (DAGL) inhibitor RHC-80267, suggesting that the secretion of these FFA during Fas-induced apoptosis is mediated by the generation of DAG by a PC-PLC activity and, sequentially, by a 1-DAGL activity which generates the FFA from its sn-1 position. The endocannabinoid 2-arachidonoyl glycerol (2-AG) should be generated as a sub-product of this pathway, but it did not accumulate inside the cells nor was secreted into the supernatant. Interestingly, the complete inhibition of free AA secretion during Fas-induced apoptosis was only achieved by using the AA trifluoromethylketone, which not only inhibits all types of phospholipase-A(2) (PLA(2)) activities, but also the described lytic activities on 2-AG. Using a combination of RHC-80267 and the iPLA(2)-specific inhibitor bromoenol lactone, it was shown that the DAGL pathway also cooperates with iPLA(2) in the generation of free arachidonate.
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PMID:Characterization of the lipolytic pathways that mediate free fatty acid release during Fas/CD95-induced apoptosis. 1621 85


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