Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.4.3 (phospholipase C)
18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The physiological significance of glutathione in the mammalian central nervous system is still uncertain, although some evidence indicates that it may be an important regulatory peptide. In the present study, the distribution and characteristics of glutathione binding sites in the brain have been studied. Biotinyl-glutathione was synthesized as a probe to detect glutathione binding sites in the CNS. Specific glutathione binding sites in the brain were largely localized to the white matter, suggesting the presence of glutathione receptors on neuroglial cells. The colloidal gold technique and immunofluorescence double staining allowed the visualization of the receptor at the cellular level and thus demonstrated that there are glutathione receptors on cultured astrocytes. Glutathione applied to cultured astrocytes elicited increased levels of intracellular inositol-1,4,5-trisphosphate, suggesting that glutathione receptors were coupled to phospholipase C. The localization of glutathione receptors on astrocytes and the activation of a second messenger system by glutathione suggest that glutathione may be a neuropeptide in the central nervous system.
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PMID:Glutathione: new candidate neuropeptide in the central nervous system. 133 27

Thiol:protein-disulfide oxidoreductase catalyzes the GSH reduction of protein disulfides to sulfhydryls. Chromatography of solubilized hepatic microsomes on Mono Q yielded two peaks, Q-2 and Q-5, which contained all the thiol:protein-disulfide oxidoreductase activity. These were further purified by chromatofocusing giving specific activities of 14.4 and 45.9 nmol/mg of protein/min, respectively with purifications of 45.0- and 143.6-fold. Amino acids 1-18 of Q-5 were the same as previously reported for Thiol:protein-disulfide oxidoreductase (Edman, J. C., Ellis, L., Blacher, R. W., Roth, R. A., and Rutter, W. J. (1985) Nature 317, 267-270), except amino acid 1 was leucine instead of aspartate and amino acid 6 was asparagine instead of glutamate. The N-terminal amino acid sequence of Q-2 differed markedly from Q-5 but Q-2 showed 100% identity at amino acids 25-54, 258-269, 285-310, 347-350, 412-419, and 434-463 for the reported sequence of rat, hepatic, cytosolic phosphatidylinositol-specific phospholipase C form 1a (PLC) (Bennett, C. F., Balcarek, J. M., Varrichio, A., and Crooke, S. T. (1988) Nature 334, 268-270). PLC activity was found in the elution from the Mono Q column, but none was found in purified Q-2 or Q-5. Antibodies to Q-5 reacted with Q-2, but anti-Q-2 did not react with Q-5. Anti-Q-2 antibody showed immunoreactivity with 55- and 60-kDa microsomal proteins, whereas Q-5 antibody reacted with a number of microsomal proteins. Although Q-2 was immunoreactive with a polyclonal antibody to guinea pig, uterine cytosolic PLC, partially purified PLCs from rat liver cytosol did not react to this antibody. Our data would suggest that the published sequence for PLC form 1a may actually be the sequence for Q-2.
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PMID:Purification and characterization of a new isozyme of thiol:protein-disulfide oxidoreductase from rat hepatic microsomes. Relationship of this isozyme to cytosolic phosphatidylinositol-specific phospholipase C form 1A. 165 21

4-Hydroxynonenal (HNE) is a major end-product of lipid peroxidation. 1 mM HNE inhibits the activity of liver phospholipase C (PL-C) and this effect is prevented by 1 mM GSH; on the contrary GSH is unable to counteract the stimulation of PL-C induced by a low concentration of HNE (100 nM). Other hydroxyalkenals are able to stimulate PL-C at low doses (micromolar or less), the most effective being 4-hydroxyoctenal which acts at picomolar doses. The lack of a correlation between the chain length of the aldehydes used and the degree of PL-C stimulation seems to exclude the possibility that their effect could be due to an aspecific solvent action toward the phosphatidylinositol-4,5-diphosphate used as substrate for the enzymatic assay.
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PMID:[Influence of reduced glutathione on changes in the activity of phospholipase C induced by 4-hydroxynonenal]. 262 27

We have examined the direct effects of oxidant metabolites on cardiac sarcolemmal phosphoinositide phospholipase C which transduces signals from various receptors for the modulation of intracellular Ca2+ levels. The enzyme activity in rat cardiac sarcolemmal membranes that had been preincubated (10 min; 37 degrees C) with xanthine-xanthine oxidase, a superoxide anion generating system, was not significantly affected. The addition to this system of superoxide dismutase, which converts superoxide anion to hydrogen peroxide (H2O2), resulted in a significant decrease of the enzyme activity in comparison with control values. Such decrease was fully prevented by catalase. Preincubation of sarcolemma with hypochlorous acid also gave a significant inhibition of phospholipase C, which was counteracted by the synthetic thiol reducer dithiothreitol. H2O2-pretreatment induced a concentration-dependent inhibition of the enzyme which was prevented by catalase but not by the iron chelator deferoxamine. Dithiothreitol was able to protect against, as well as to recover the enzyme activity from the H2O2 effects. These data suggest that superoxide anions and hydroxyl radicals did not interfere with phospholipase C activity, and that the nonradical oxidants, H2O2 and hypochlorous acid, may have acted through oxidation of thiol (SH) groups. The existence of reactive SH groups associated with the enzyme was confirmed by the inhibitory effects of SH modifiers (p-chloromercuriphenylsulfonic acid, 5'5'-dithio-bis(2-nitrobenzoic acid), N-ethylmaleimide and methyl methanethiosulfonate), which were prevented and in some cases also reversed by dithiothreitol. The biological reducer glutathione (GSH) was not able to recover the H2O2-induced inhibition of phospholipase C, whereas its oxidized form (GSSG) decreased the enzyme activity both in control and H2O2-pretreated membranes. The enzyme was active in a wide range of GSH/GSSG redox states, but H2O2 pretreatment narrowed this range. The results showed that oxidative stress changed the redox state of sarcolemmal phospholipase C, and this deactivated the enzyme. The oxidants' concentrations that significantly impaired phospholipase C in this study were compatible with those occurring in vivo during ischemia-reperfusion [Am. J. Med. 91(Suppl. 3C):235, 1991]. This supports the possibility that alteration of the receptor-associated phospholipase C may be a factor in the oxidant-related dysfunction of the ischemic-reperfused heart.
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PMID:Oxidative stress modifies the activity of cardiac sarcolemmal phospholipase C. 828 Jul 55

Thapsigargin depletes intracellular Ca2+ stores by its inhibitory effect on the Ca2+ pumps, which unmasks an aspecific Ca2+ leak from the stores. This aspecific Ca2+ permeability of the stores was further investigated using 45Ca2+ fluxes on intact and permeabilized A7r5 smooth-muscle cells. Stores in intact cells were found to be more leaky for Ca2+ than those in saponin-permeabilized or Staphylococcus aureus alpha-toxin-permeabilized cells, which suggests that a cytosolic factor may be involved. Supplementing the medium bathing the permeabilized cells with a submaximal Ins(1,4,5)P3 concentration increased the leakiness of the stores. Glutathione also increased the aspecific Ca2+ leak. This effect occurred with both the reduced and the oxidized form but reduced glutathione was more effective. Our data show that basal Ins(1,4,5)P3 levels and glutathione can contribute to the relatively high Ca2+ leak in intact cells. The washing out of these substances during permeabilization can reduce the aspecific leakiness of the stores.
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PMID:Ins(1,4,5)P3 and glutathione increase the passive Ca2+ leak in permeabilized A7r5 cells. 850 39

It is an established fact that animals recovering from prior acute renal failure (ARF) are resistant to subsequent renal failure challenge with the same toxic agents, although the detailed mechanisms responsible for this phenomenon remain unclear. In this study, the mechanism underlying acquired resistance to gentanmicin (GM) was investigated from the viewpoint of kidney tissue enzymology. Sprague-Dawley rats (N = 40) were administered GM subcutaneously at the dose of 80mg/day consecutively for 40 days. Blood urea nitrogen (BUN) reached the maximum mean concentration of 36 mg/dl on day 14. Thereafter, it decreased to a level within the normal range on day 21. The change in fractional excretion of sodium (FENa) showed a curve virtually identical to the change in BUN. In renal tissue, the elevation of malondialdehyde (MDA) levels was transient during continued administration of GM. The shingomyelin (SPH)/phosphatidylcholine (PC) ratio significantly decreased on day 4, but there was no marked change thereafter. The levels of total phospholipids (PLs), phosphatidylcholine (PC), and phosphatidylethanolamine (PE) increased, whereas SPH decreased mostly on day 4. The levels of phosphatidylinositol (PI) showed a continued fall during the 40 days of the experiment. On day 40, these changes in composition recovered. Phospholipase A2 (PLA2) activities decreased gradually, whereas a distinct increase in phospholipase C (PLC) activity was maintained after day 21. Furthermore, glutathione (GSH) levels also showed two distinct cycles of decrease and increase. PLs levels correlated well with PLC activities. It was concluded that accelerated lipid peroxidation occurs early in the course of GM administration and enhances changes in the phospholipid composition, which has an influence on membrane fluidity. Thus, acquired resistance to ARF induced by GM may be due to the supply of GSH and the maintenance of alteration in phospholipid composition, which are induced by PLC activities.
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PMID:[An experimental study on the pathogenetic role of acquired resistance to acute renal failure--Enzymochemical investigation]. 871 8

Oxidative stress appears to contribute to neuronal dysfunction associated with Alzheimer's disease and other CNS neurodegenerative disorders. This investigation examined if oxidative stress might contribute to impairments in cholinergic receptor-linked signaling systems and if intracellular glutathione levels modulated responses to oxidative stress. To do this the activation of the AP-1 and NF-kappaB transcription factors and of the phosphoinositide second-messenger system was measured in human neuroblastoma SH-SY5Y cells after exposure to the oxidants H2O2 or diamide, with or without prior depletion of cellular glutathione. H2O2 concentration-dependently inhibited carbachol-stimulated AP-1 activation and this inhibition was potentiated in glutathione-depleted cells. Carbachol-stimulated NF-kappaB activation was unaffected by H2O2 unless glutathione was depleted, in which case there was a H2O2 concentration-dependent inhibition. Glutathione depletion also potentiated the inhibition by H2O2 of carbachol- or G-protein (NaF)-stimulated phosphoinositide hydrolysis, whereas phospholipase C activated by the calcium ionophore ionomycin was not inhibited. The thiol-oxidizing agent diamide also inhibited phosphoinositide hydrolysis stimulated by carbachol or NaF, and glutathione depletion potentiated the diamide concentration-dependent inhibition. Unlike H2O2, diamide also inhibited ionomycin-stimulated phosphoinositide hydrolysis. Activation of both AP-1 and NF-kappaB stimulated by carbachol was inhibited by diamide, and glutathione depletion potentiated the inhibitory effects of diamide. Thus, diamide inhibited a wider range of signaling processes than did H2O2, but glutathione depletion increased the susceptibility of phosphoinositide hydrolysis and of transcription factor activation to inhibition by both H2O2 and diamide. These results demonstrate that the vulnerability of signaling systems to oxidative stress is influenced by intracellular glutathione levels, indicating that cell-selective susceptibility to inhibition of signal transduction systems by oxidative stress can arise from cellular variations in antioxidant capacity.
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PMID:Glutathione depletion exacerbates impairment by oxidative stress of phosphoinositide hydrolysis, AP-1, and NF-kappaB activation by cholinergic stimulation. 947 71

Previously, we reported that PC12 cells showed increased vulnerability to oxidative stress (OS) induced by H2O2 (as assessed by decrements in calcium recovery, i.e., the ability of cells to buffer Ca(2+) after a depolarization event) when the membrane levels of cholesterol (CHL) and sphingomyelin (SPH) were modified to approximate those seen in the neuronal membranes of old animals. The present study was designed to examine whether the enrichment of the membranes with SPH-CHL and increased cellular vulnerability to OS are mediated by neutral SPH-specific phospholipase C (N-Sase) and the intracellular antioxidant GSH. The results showed a significant up-regulation of N-Sase activity by both low (5 microM) and high (300 microM) doses of H2O2. However, under high doses of H2O2 the up-regulation of N-Sase is accompanied by a significant increase in reactive oxygen species and by a decrease in intracellular GSH. The enrichment of membranes with SPH-CHL significantly potentiated the effects of high doses of H2O2, by further reducing the intracellular GSH and further up-regulating the N-Sase activity. Furthermore, repleting intracellular GSH with 20 mM N-acetylcysteine treatment was sufficient to attenuate the effect of a low dose of H2O2 on Ca(2+) recovery in SPH-CHL-treated cells. Thus, these results suggested that age-related alterations in the membrane SPH-CHL levels could be important determinants of the susceptibility of neuronal cells to OS.
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PMID:Role of membrane lipids in regulation of vulnerability to oxidative stress in PC12 cells: implication for aging. 1129 65

Glutathione S-transferases (GST) are multifunctional proteins. alpha class GSTs are known to catalyze glutathione peroxidase reactions, in addition to their major activity, i.e., conjugation of electrophiles to glutathione. In the present work, the contribution of rat and mouse alpha class GSTs to glutathione-dependent reduction of phospholipid hydroperoxides has been studied., Results of these studies indicate that the alpha class GST fraction, which consists of three isoforms, has glutathione peroxidase activity toward phospholipid hydroperoxides residing in biological membranes, without the need of prior phospholipase C action. Immunotitration studies using antibodies specific to the alpha class GSTs, GSTA1-1, GSTA2-2, and GSTA3-3, indicate that these GST isozymes account for approximately half of the glutathione peroxidase activity toward phospholipid hydroperoxides present in the 28,000g supernatant fractions of rat and mouse liver extracts. GSTs contribute proportionally lesser fraction of this activity in other tissues in which alpha class GSTs are less prevalent. In mice, the contribution of alpha class GSTs to the overall glutathione peroxidase activity is indistinguishable in wild-type mice and knockout mice lacking the major selenoenzyme, glutathione peroxidase 1, an enzyme that does not act on intact phospholipid hydroperoxides. These results are consistent with our previous studies on human alpha class GSTs (Yang, et al. J. Biol. Chem. 276, 19220-19230, 2001) and demonstrate that alpha class GSTs are of physiological importance, not only in the conjugative detoxification of electrophiles, but are also an essential component of cellular antioxidant defense mechanisms.
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PMID:Role of alpha class glutathione S-transferases as antioxidant enzymes in rodent tissues. 1214 Jan 74

Xanthic acids have long been known to act as reducing agents. Recently, D609, a tricyclodecanol derivative of xanthic acid, has been reported to have anti-apoptotic and anti-inflammatory properties that are attributed to specific inhibition of phosphatidyl choline phospholipase C (PC-PLC). However, because oxidative stress is involved in both of these cellular responses, the possibility that xanthates may act as antioxidants was investigated in the current study. Finding that xanthates efficiently scavenge hydroxyl radicals, the mechanism by which D609 and other xanthate derivatives may protect against oxidative damage was further examined. The xanthates studied, especially D609, mimic glutathione (GSH). Xanthates scavenge hydroxyl radicals and hydrogen peroxide, form disulfide bonds (dixanthogens), and react with electrophilic products of lipid oxidation (acrolein) in a manner similar to GSH. Further, upon disulfide formation, dixanthogens are reduced by glutathione reductase to a redox active xanthate. Supporting its role as an antioxidant, D609 significantly (p < 0.01) reduces free radical-induced changes in synaptosomal lipid peroxidation (TBARs), protein oxidation (protein carbonyls), and protein conformation. Thus, in addition to inhibitory effects on PC-PLC, D609 may prevent cellular apoptotic and inflammatory cascades by acting as antioxidants and novel GSH mimics. These results are discussed with reference to potential therapeutic application of D609 in oxidative stress conditions.
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PMID:Derivatives of xanthic acid are novel antioxidants: application to synaptosomes. 1274 29


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