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 interaction of feline leukaemia viruses (FeLV) with erythrocytes was investigated. Haemadsorption (HAd) was observed on the surface of feline embryonic fibroblast cells infected with FeLV. HAd was detected in various degrees when cat, hamster or horse erythrocytes were incubated with cells infected with viruses of subgroup C (FeLV-C) and on cells infected with some FeLV subgroup A viruses (FeLV-A), but not on cells infected with FeLV subgroup B viruses (FeLV-B). HAd of sheep erythrocytes was detected on cells infected with some FeLV-C viruses. The HAd of hamster erythrocytes on cells infected with FeLV-C/Sarma virus was inhibited by antisera against gp70 or p15(E) but not by sera to the other FeLV structural polypeptides. HAd inhibition was also exhibited by cat sera which had FeLV-neutralizing activity but not by sera of specific pathogen-free cats. Haemagglutination by FeLV-C viruses was demonstrated after the virus was treated with neuraminidase and phospholipase C, or Tween-80 and ether. Contrary to expectations from the pattern observed by HAd, all FeLV-A viruses had similar haemagglutinin (HA) activity to FeLV-C viruses. FeLV-B viruses did not possess an HA.
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PMID:Haemadsorption and haemagglutination by feline leukaemia viruses. 298 74

The main electric organ of Electrophorus electricus is particularly rich in thiamine triphosphate, which represents 87% of the total thiamine content in this tissue. The thiamine pyrophosphate concentration, however, is very low in the eel electric organ and skeletal muscle as compared with other eel or rat tissues. Furthermore, electroplax membranes contain a whole set of enzymes responsible for the dephosphorylation of thiamine tri-, pyro- and monophosphate. Thiamine triphosphatase has a pH optimum of 6.8 and is dependent on Mg2+. The real substrate of the enzyme is probably a 1:1 complex of Mg2+ and thiamine triphosphate. Thiamine pyrophosphatase is activated by Ca2+. The apparent Km for thiamine triphosphate and Vmax are found to be, respectively, 1.76 mM and 5.95 nmol/mg of protein/min. Thiamine triphosphatase activity is inhibited at physiological K+ concentrations (up to 90 mM) and increasing Na+ concentrations (50% inhibition at 300 mM). ZnCl2 (10 mM) inhibits 90% of the enzyme activity. ATP and ITP are also strongly inhibitory. No significant effect of neurotoxins is seen. Membrane-associated thiamine triphosphatase is affected differently by proteolytic enzymes and is partially inactivated by pretreatment with phospholipase C and neuraminidase. The physiological significance of thiamine triphosphatase is discussed in relation to a specific role of thiamine in the nervous system.
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PMID:Thiamine triphosphate and membrane-associated thiamine phosphatases in the electric organ of Electrophorus electricus. 303 30

The effect of a variety of proteolytic, glycosidic and lipid hydrolyzing enzymes on the ability of mouse egg plasma membrane to interact with sperm was evaluated in this study. Zona-free mouse eggs were exposed to enzymes at various concentrations, washed, and inseminated; the number of sperm attached to or having penetrated the egg plasma membrane was determined at 20 and 180 min post-insemination, respectively. The proteases trypsin and chymotrypsin caused concentration-dependent reductions in both sperm attachment and sperm penetration levels when eggs were incubated at enzyme concentrations ranging from 1- to 1000 micrograms/ml for 30 min prior to insemination. Time-course studies revealed significant inhibition of both sperm attachment and sperm penetration levels after treating zona-free eggs for 5 min at 1000 micrograms/ml of either trypsin or chymotrypsin. Several of the phospholipases tested, including phospholipases C, D, and A2, had no inhibitory effect on sperm penetration levels, with phospholipase C and A2 (100 micrograms/ml) causing inhibition of sperm attachment. Of the glycosidic enzymes evaluated, glucuronidase (1000 micrograms/ml) caused significant inhibition of sperm binding but not sperm penetration, and glucosidase, galactosidase, and neuraminidase had no effect on either sperm attachment or sperm penetration. These findings indicate that the ability of the mouse egg plasma membrane to fuse with sperm can be preferentially altered by treatment with proteases.
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PMID:Enzymatic alteration of the ability of mouse egg plasma membrane to interact with sperm. 306 84

To investigate in vitro interactions between gliadin peptide fractions that have been shown to be toxic to celiac small intestinal mucosa in humans and small intestinal microvillus membranes (MVM) from rats during postnatal maturation, MVM were prepared from newborn, 18-day-old preweanling, and adult rats. Partially hydrolyzed gliadin peptide fractions B1-B4, and the pure gliadin peptide B3142 were radioiodinated and used for binding assays. Miniature ultracentrifugation was used for separation of unbound material. Binding of gliadin fractions to MVM was weak and nonspecific in terms of lacking saturation and inhibition. There was no inhibition of binding by mannan. Enzyme pretreatment of MVM (trypsin, neuraminidase, phospholipase C) did not result in any significant change of binding. Compared with peptides prepared from bovine serum albumin as a control, there was no significant difference in binding of gliadin peptide fractions to MVM. Thus, a lectin-like effect of gliadin peptides toward MVM, or the existence of a specific intestinal surface receptor for gliadin peptides appeared improbable. There were, however, consistent maturational changes in MVM binding in that newborn MVM bound more B1-B4 and B3142 compared with adult controls (p less than 0.001). Nonspecific binding of gliadin fractions to MVM might be related to the initiation of nonspecific in vitro effects of gliadin, particularly toward the immature small intestine. The MVM binding model in the rat clearly does not provide a system for studying celiac disease pathogenesis, but it might help clarify basic processes in the interaction between food-derived substances and elements of the gastrointestinal mucosal barrier.
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PMID:Food proteins and maturation of small intestinal microvillus membranes (MVM). II. Binding of gliadin hydrolysate fractions and of the gliadin peptide B3142. 333 72

Saturable bilirubin binding to human erythrocyte membranes was measured before and after digestion with neuraminidase and phospholipases. Neuraminidase-treated erythrocyte membranes did not show any change in their binding properties, indicating that gangliosides could be excluded as candidates for saturable bilirubin-binding sites on erythrocyte membranes. Although bilirubin-binding properties of the membranes did not change after phospholipase D digestion, either, phospholipase C treatment greatly enhanced bilirubin binding. Thus it is suggested that a negatively charged phosphoric acid moiety of phospholipids on the membrane surface may play a role to prevent a large amount of bilirubin from binding to the membranes. Further saturable bilirubin binding to inside-out sealed erythrocyte membrane vesicles showed values comparable with those of the right-side-out sealed membranes, suggesting that the bilirubin-binding sites may be distributed on both outer and inner surfaces of the membranes, or may exist in the membranes where bilirubin may be accessible from either side.
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PMID:Interaction of bilirubin with human erythrocyte membranes. Bilirubin binding to neuraminidase- and phospholipase-treated membranes. 343 38

Qualitative and quantitative changes in neural cell adhesion molecule (N-CAM) protein and mRNA forms were measured during myogenesis in G8-1 and C2 cell lines. Indirect immunofluorescence assay showed that N-CAM was constitutively expressed by myoblasts in culture and that myotubes appeared to be stained more strongly. These changes were quantified using a dot blot assay. N-CAM levels increased almost 4-fold in G8-1 cells and 15-fold in C2 cells during myogenesis. The kinetics of accumulation of N-CAM were not coordinate with other muscle markers such as creatine kinase or acetylcholine receptor levels, since N-CAM accumulated significantly ahead of these markers. Immunoblotting showed that myogenesis was not associated with changes in the extent of sialylation of N-CAM. However, distinct changes in desialo forms were observed after neuraminidase treatment. Myogenesis was accompanied by increases in 125- and 155-kD desialo forms with minor changes in 120- and 145-kD forms. Biosynthetic labeling studies showed that myoblasts specifically expressed a transmembrane isoform of 145 kD that was phosphorylated and was down-regulated in myotubes. Pulse-chase analysis of myotubes showed that the 120-kD isoform and an isoform of 145 kD that co-migrated with, but was distinct from, the 145 kD transmembrane isoform of myoblasts were precursors of the 125- and 155-kD isoforms, respectively, that accumulated in myotubes. The 125- and 155-kD isoforms in myotubes are linked to the cell membrane via phosphatidylinositol linkage and can be released by phospholipase C. Indirect immunofluorescence analysis showed that phosphatidylinositol specific phospholipase C specifically released N-CAM from the myotube membrane generating N-CAM-free myotubes, while myoblasts were unaffected by this treatment. Three N-CAM mRNA species were observed in mouse muscle cell lines. Myoblasts were characterized by their expression of 6.7- and 5.2-kb transcripts while myotubes express 5.2- and 2.9-kb transcripts. Thus, myogenesis is qualitatively associated with a down regulation of the 6.7-kb transcript and an up regulation of the 5.2- and 2.9-kb transcript.
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PMID:Skeletal muscle neural cell adhesion molecule (N-CAM): changes in protein and mRNA species during myogenesis of muscle cell lines. 365 57

The major source of rat serum alkaline phosphatase (ALP) is well known to be from the intestinal enzyme, but it is still unclear whether it is from the duodenal or the ileal enzyme. The organic origin was investigated by means of two-dimensional electrophoresis. Major isoelectric points and molecular masses for activities of duodenal enzyme treated with both phosphatidylinositol-specific phospholipase C and neuraminidase were identified apparently with those of the major serum enzyme. In organ culture, the normal duodenal enzyme was released in the highest amounts to the culture medium. These results indicate that the major source of serum ALP in adult rats is basically from the duodenal enzyme. On the other hand, lectin affinity chromatography for ALPs showed that the ALP in the medium from culture duodenum and liver had the same complex-type sugar chain as with the ALP in the duodenal tissue. Although the duodenal ALP induced by glucosamine in vitro had the hybrid-type chain, sugar chains of the induced ALP in the culture medium were of the complex type, indicating that medial ALPs possessing the same sugar chain as the native duodenal enzyme, complex type, are mainly released from their tissues in normal conditions.
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PMID:Blood appearance of rat alkaline phosphatase originating from the duodenum in vitro. 369 1

The desialylation of chick brain microsomal membranes affects the transbilayer distribution of phospholipids. When intact microsomes were treated with neuraminidase, less phosphatidylcholine and sphingomyelin could be hydrolysed with phospholipase C under experimental conditions which allowed the hydrolysis of the phospholipids of the external leaflet only. In contrast, the accessibility of phosphatidylethanolamine and phosphatidylserine to the external probes (trinitrobenzene sulfonic acid or phospholipase C) was not affected. After neuraminidase treatment of a microsomal fraction, less phosphatidylcholine, newly synthesized through the cytidine pathway, could be hydrolysed by phospholipase C, whereas the reaction of newly synthesized phosphatidylethanolamine molecules with trinitrobenzene sulfonic acid was not affected. The results suggest that in biological membranes some choline phospholipid molecules may interact with the sialyl residue of sialocompounds. This interaction may contribute to the maintenance of phospholipid asymmetry in brain membranes.
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PMID:Effect of neuraminidase treatment on the topological distribution of phospholipids in chick brain microsomes. 373 Mar 82

Since mixtures of lipids alone are known to elicit membrane fusion without participation of fusion proteins, the role of viral lipids in the so-called virus-induced hemolysis and cell fusion has been investigated, using as a model the fowl plague virus (influenza A/FPV/Rostock/H7N1). The experiments were planned in a way that allowed quantitative modification of viral lipids without changing envelope glycoproteins. Under the conditions employed, cholesterol oxidase of Nocardia erythropolis and phospholipase C of Bacillus cereus were shown to completely modify their substrates in the virus without altering virus-associated hemagglutinating and neuraminidase activities. It was found with such enzyme treatment that virus-induced hemolysis and cell fusion are greatly influenced by cholesterol and phospholipids of the envelope. It became clear, that hemolysis and fusion are differently dependent on the nature of lipid components even though mediated by the same viral glycoproteins.
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PMID:Interplay between lipids and viral glycoproteins during hemolysis and fusion by influenza virus. 375 42

Excitation-contraction coupling in cardiac muscle is dependent on extracellular calcium and calcium bound to the surface of the myocardial cell. In this study, we examined the physical characteristics of calcium binding to adult guinea pig ventricular myocytes disaggregated mechanically in oxygenated tissue culture medium containing a proteinase inhibitor (aprotinin), and separated from cellular debris by Cytodex beads. Cells prepared in this manner excluded Trypan blue and showed no evidence of spontaneous contraction or contracture. Scatchard plots of calcium binding determined by continuous flow equilibrium dialysis revealed a high-affinity, low-capacity pool, Ka = 65 X 10(3) M-1 and Bt = 1.3 nmol X mg-1 and a low-affinity, high-capacity pool, Ka = 141 M-1 and Bt = 138 nmol X mg-1. The low-affinity pool was not detectable after lanthanum, trypsin or collagenase treatment or in cells prepared without aprotinin in the isolation medium. Both neuraminidase and phospholipase C reduced Bt of the low-affinity pool by one half, but only neuraminidase affected the affinity constant of this pool. Ka was increased to 516.7 M-1, similar to the apparent affinity constant for calcium binding estimated from dP/dtmax measured at several extracellular calcium concentrations (470 M-1). The results suggest that calcium bound to sarcolemmal phospholipids represents the superficial calcium involved in excitation-contraction coupling in the heart.
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PMID:Calcium binding to cardiac myocytes protected from proteolytic enzyme activity. 398 17


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