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

---

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

A cytotoxic protein isolated from Pseudomonas aeruginosa damages the plasma membranes of many mammalian cells by forming pores. We studied binding of the 125I-cytotoxin and the resulting increase of cation permeability in erythrocytes of various mammalian species. The sensitivity of red blood cells was inversely related to the relative sphingomyelin content in their external surface. Thus, erythrocytes with a sphingomyelin to phosphatidylcholine ratio below 1 (dog, rat, rabbit and man) were sensitive, whereas red blood cells with a ratio above 1 (pig, cattle and sheep) were not attacked even with 100-fold higher cytotoxin concentrations. At 37 degrees C 6.8 +/- 1.2 x 10(3) molecules of 125I-cytotoxin were bound per rabbit erythrocyte (KD = 59 nM), whereas no binding occurred to cattle cells. Cleavage of sphingomyelin by sphingomyelinase C from Bacillus cereus (EC 3.1.4.12) triggered a dose-dependent enhancement in binding and permeability increase, particularly in red blood cells with a high proportion of sphingomyelin. The KDs for all animal species investigated were 53-60 nM. Pretreatment with mainly phosphatidylcholine-hydrolyzing phospholipases D from Streptomyces chromofuscus and cabbage (EC 3.1.4.4) or phospholipase C from Bacillus cereus (EC 3.1.4.3) did not influence the cytotoxin effect. The negative correlation between susceptibility and the proportion of sphingomyelin in plasma membranes suggests a binding site close to sphingomyelin.
...
PMID:Pseudomonas aeruginosa cytotoxin: the influence of sphingomyelin on binding and cation permeability increase in mammalian erythrocytes. 250 11

We describe methods for automated enzymatic measurement of lecithin, sphingomyelin, and phosphatidylglycerol in amniotic fluid. Phospholipase C (EC 3.1.4.3) and sphingomyelin phosphodiesterase (EC 3.1.4.12) are reacted with lecithin and sphingomyelin, respectively, to liberate phosphocholine. Phosphocholine is then reacted with alkaline phosphatase, choline oxidase, peroxidase, and 4-aminoantipyrine to form a colored complex, for which the absorbance at 500 nm is measured with a centrifugal analyzer. Phosphatidylglycerol is hydrolyzed by phospholipase D (EC 3.1.4.4) to form glycerol, which is subsequently reacted with ATP and NAD+ in the presence of glycerol kinase and glycerol-3-phosphate dehydrogenase to yield NADH. The absorbance of the NADH formed is measured at 340 nm. These methods provide a simple, rapid, and accurate alternative to thin-layer chromatography for determination of phospholipids in amniotic fluid for assessment of fetal lung maturity.
...
PMID:Automated enzymatic measurement of lecithin, sphingomyelin, and phosphatidylglycerol in amniotic fluid. 380 1

We describe a method for the direct enzymatic determination of phosphatidylcholine and sphingomyelin in serum. Phospholipase C (EC 3.1.4.3) and sphingomyelinase (EC 3.1.4.12) are used to hydrolyze phosphatidylcholine and sphingomyelin, respectively, with high specificity; alkaline phosphatase (EC 3.1.3.1) is used to cleave inorganic phosphorus. The choline group, after oxidation with choline oxidase (EC 1.1.3.17), is detected with 4-aminoantipyrine. Alternatively, phosphorus is assayed with metavanadate. The excellent agreement between results of this modification of a procedure described by Artiss et al. (Microchem. J. 26: 1017, 1980) for amniotic fluid and of the conventional thin-layer chromatographic method makes this an attractive method for determination of both phospholipid subclasses in serum.
...
PMID:Enzymic assay for phosphatidylcholine and sphingomyelin in serum. 634 Aug 53

We describe a simple turbidometric assay for phosphatidylcholine-specific phospholipase C (PC-PLC) (EC 3.1.4.3), phosphatidylinositol-specific phospholipase C (PI-PLC) (EC 3.1.4.10), and sphingomyelinase (SMase) (EC 3.1.4.12), suitable for high-volume screening using unmodified substrates. Under the conditions described, 1 to 10 U/ml of PC-PLC (Bacillus cereus) induces a rapid and continuous increase in turbidity (0.4 to 0.6 AU at 410 nm) of phosphatidylcholine vesicles (1-10 mM) that highly correlates with hydrolysis. Turbidity increases with the formation of small homogenous particles, which is enzyme and substrate dependent. Analogously, PI-PLC (1-10 U/ml) causes a continuous increase in the turbidity of PI vesicles. SMase also causes a continuous increase in PC vesicle turbidity, but unlike like the glycerol phospholipases, SMase causes a discontinuous increase in vesicles of its proper substrate sphingomyelin (SM). After 8-15% hydrolysis, SM vesicles are converted to large heterogeneous particles permitting detection of SMase activity by visual inspection. Thus, turbidity is a useful property to monitor SMases and C-type phospholipases that cleave vesicle-forming phospholipids. Furthermore, the assay is designed for the microtiter plate format, enabling the continuous and simultaneous monitoring of up to 96 wells.
...
PMID:A turbidometric assay for phospholipase C and sphingomyelinase. 786 73

The effect of sphingomyelin hydrolysis on triacylglycerol-rich lipoprotein secretion was examined in the human intestinal cell line, CaCo-2. Addition of sphingomyelinase decreased sphingomyelin and phosphatidylethanolamine by 60 and 20%, respectively. Sphingomyelin hydrolysis decreased the basolateral secretion of triacylglycerol mass, newly synthesized triacylglycerol, and apo B mass. Pulse-chase experiments with [35S]methionine demonstrated a decrease in apo B synthesis and a marked decrease in apo B100 and apo B48 secretion without altering apo A1 secretion. Sphingomyelin hydrolysis did not change apo B mRNA levels nor apo B turnover. Phosphatidylcholine-specific phospholipase C did not decrease apo B synthesis or its basolateral secretion. Membrane protein kinase C (PKC) activity was decreased twofold after sphingomyelin hydrolysis. The PKC inhibitor staurosporine decreased apo B mass and newly synthesized apo B secretion. Sphingomyelinase and staurosporine together caused an additional decrease in apo B secretion suggesting that sphingomyelin hydrolysis decreased apo B secretion independently of its effect on PKC activity. Moreover, conditions that increase PKC activity did not increase apo B secretion. Cell-permeable analogs of ceramide decreased immunoreactive apo B secretion. Sphingosine was without effect. The hydrolysis of membrane sphingomyelin by intestinal or pancreatic neutral sphingomyelinase may lead to the accumulation of cellular ceramide, which, in turn, could inhibit triacylglycerol-rich lipoprotein secretion.
...
PMID:Release of ceramide after membrane sphingomyelin hydrolysis decreases the basolateral secretion of triacylglycerol and apolipoprotein B in cultured human intestinal cells. 825 18

Recent investigations suggest that tumor necrosis factor (TNF)-alpha may utilize the sphingomyelin pathway for signal transduction. Signaling in this system involves hydrolysis of sphingomyelin to ceramide by action of a neutral sphingomyelinase and stimulation of a ceramide-activated protein kinase (Dressler, K. A., Mathias, S., and Kolesnick, R. N. (1992) Science 255, 1715-1718). To clarify the role of this pathway in TNF action, the present studies assessed the effect of the sphingomyelin pathway on activation of nuclear factor kappa B (NF-kappa B), an event considered integral to the transfer of the TNF message to the cell nucleus. As shown previously, TNF (1 nM) induced a marked increase in nuclear NF-kappa B binding in human leukemia (HL-60) cells within 5 min, and elevated binding was detected for as long as 1 h. Addition of a maximally effective concentration of sphingomyelinase, 0.1 units.ml-1, induced a 50% reduction in sphingomyelin content by 5 min from a basal level of 560 pmol.10(6) cells-1 and a quantitative increase in ceramide levels from 89 pmol.10(6) cells-1. Sphingomyelinase 0.1 units.ml-1 also induced an increase in nuclear NF-kappa B binding within 5 min, an effect measurable for as long as 1 h. As little as 1 x 10(-5) units.ml-1 sphingomyelinase was effective and a maximal effect occurred with 1 x 10(-3) units.ml-1. A cell-permeable ceramide analog, C8-ceramide, which mimics biologic effects of TNF-alpha, also enhanced nuclear NF-kappa B activation within minutes. In contrast, addition of a phospholipase C or a synthetic diacylglycerol (DG) analog, 1,2-dioctanoylglycerol, failed to enhance nuclear NF-kappa B binding despite large increases in cellular DG content. Further, TNF-alpha induced elevation in ceramide content by 2 min to 185% of control but did not affect DG levels. These studies provide evidence that stimulation of the sphingomyelin pathway leads to NF-kappa B activation in HL-60 cells.
...
PMID:Tumor necrosis factor activation of the sphingomyelin pathway signals nuclear factor kappa B translocation in intact HL-60 cells. 837 8

I have investigated the effects of human urinary neutral sphingomyelinase (N-SMase) (Chatterjee, S., and Ghosh, N. (1989) J. Biol. Chem. 264, 12554-12561) on the cell-surface binding, internalization, and degradation of 125I-low density lipoprotein (LDL) and on cholesteryl ester synthesis in cultured human fibroblasts. N-SMase exerted a concentration-dependent continuous stimulation of 125I-LDL cell-surface binding, internalization, and degradation in normal human fibroblasts. A 3-fold increase in binding, internalization, and degradation was observed at the maximum amount (600 units of N-SMase/ml) examined. This phenomenon was accompanied by a continuous stimulation of cholesteryl ester synthesis. A 5-fold increase in cholesteryl ester synthesis was observed after incubation for 4 h with N-SMase. Antibody against N-SMase and heat inactivation of N-SMase compromised the stimulatory effects of N-SMase on 125I-LDL metabolism and cholesteryl ester synthesis in these cells. Incubation of cells with phospholipase D and phospholipase C did not alter 125I-LDL binding, internalization, or degradation. This finding suggests that the stimulatory effects of N-SMase on LDL metabolism and on cholesteryl ester synthesis in fibroblasts is specific. Moreover, unlabeled LDL competitively displaced 125I-LDL from binding to N-SMase-treated cells. None of the precursors of sphingomyelin could mimic the stimulatory effects of N-SMase on 125I-LDL metabolism in these cells. Taken together, these studies suggest that one of the biological roles of N-SMase involves modulating LDL metabolism and cholesterol metabolism in fibroblasts.
...
PMID:Neutral sphingomyelinase increases the binding, internalization, and degradation of low density lipoproteins and synthesis of cholesteryl ester in cultured human fibroblasts. 842 15

The human p55 tumor necrosis factor (TNF) receptor (TR55) initiates at least two independent signaling cascades. The acidic sphingomyelinase (A-SMase) pathway involves a phosphatidylcholine-specific phospholipase C, an endosomal A-SMase, and controls expression of multiple TNF-responsive genes through induction of transcription factors such as NF-kappaB. The neutral sphingomyelinase (N-SMase) pathway comprises a membrane-bound N-SMase, proline-directed protein kinases, as well as phospholipase A2 and appears critical for the inflammatory responses induced by TNF. While the domain of TR55 that induces A-SMase is probably identical to the death domain, the exact location and extent of a putative N-SMase activation domain are still unknown. Structure-function analysis of TR55 deletion mutants revealed a novel region of 11 amino acids at position 309-319 that is both necessary and sufficient for activation of N-SMase. The N-SMase activation domain is distinct from the death domain and incapable of induction of A-SMase, NF-kappaB, and cytotoxicity. Taken together, our results suggest that a functionally independent region of TR55 is responsible for selectively initiating the N-SMase pathway that couples to an important inflammatory signaling cascade.
...
PMID:A novel cytoplasmic domain of the p55 tumor necrosis factor receptor initiates the neutral sphingomyelinase pathway. 866 14

The early signals generated following cross-linking of Fas/APO-1, a transmembrane receptor whose engagement by ligand results in apoptosis induction, were investigated in human HuT78 lymphoma cells. Fas/APO-1 cross-linking by mAbs resulted in membrane sphingomyelin hydrolysis and ceramide generation by the action of both neutral and acidic sphingomyelinases. Activation of a phosphatidylcholine-specific phospholipase C (PC-PLC) was also detected which appeared to be a requirement for subsequent acidic sphingomyelinase (aSMase) activation, since PC-PLC inhibitor D609 blocked Fas/APO-1-induced aSMase activation, but not Fas/APO-1-induced neutral sphingomyelinase (nSMase) activation. Fas/APO-1 cross-linking resulted also in ERK-2 activation and in phospholipase A2 (PLA2) induction, independently of the PC-PLC/aSMase pathway. Evidence for the existence of a pathway directly involved in apoptosis was obtained by selecting HuT78 mutant clones spontaneously expressing a newly identified death domain-defective Fas/APO-1 splice isoform which blocks Fas/APO-1 apoptotic signalling in a dominant negative fashion. Fas/APO-1 cross-linking in these clones fails to activate PC-PLC and aSMase, while nSMase, ERK-2 and PLA2 activates are induced. These results strongly suggest that a PC-PLC/aSMase pathway contributes directly to the propagation of Fas/APO-1-generated apoptotic signal in lymphoid cells.
...
PMID:Multiple pathways originate at the Fas/APO-1 (CD95) receptor: sequential involvement of phosphatidylcholine-specific phospholipase C and acidic sphingomyelinase in the propagation of the apoptotic signal. 884 79

Tumor necrosis factor-alpha induces oligodendrocytes apoptosis, and is known to stimulate the hydrolysis of sphingomyelin to form the lipid mediator, ceramide. These data encouraged us to determine whether ceramide itself is able to induce apoptosis in oligodendrocytes. For this purpose the cell-permeable ceramide analog, C2-ceramide was used. Treatment of bovine oligodendrocyte cell cultures with this compound induced cell death in a time- and concentration-dependent manner. The induction of cell death was specifically associated with the action of C2-ceramide and could not be elicited by dioctanoylglycerol (DC8) or phorbol 12-myristate 13-acetate (PMA). Treatment of the cultures with neutral sphingomyelinase, which increased the hydrolyses of endogenous sphingomyelin, resulted in oligodendrocyte death, whereas exposure of the cells to phospholipase C and A2 did not. C2-ceramide treatment caused DNA fragmentation. Morphologic analysis of the cells showed that C2-ceramide treatment resulted in a loss of their processes, reduction of cell volume, chromatin condensation, and formation of apoptotic bodies. These results indicate that ceramide can induce oligodendrocyte apoptosis, and suggest that sphingolipid metabolism plays a key role in the regulation of this process.
...
PMID:Induction of oligodendrocyte apoptosis by C2-ceramide. 913 Feb 66


1 2 3 Next >>

---