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 effects of neuraminidase and phospholipase C on the contractility and the Ca++ -binding of guinea pig taenia coli were investigated. Potassium contracture or histamine-induced contracture of taenia coli was inhibited by treatment with neuraminidase, though acetylcholine-induced contracture was not. Treatment with phospholipase C markedly inhibited the contracture induced by isotonic potassium, histamine or acetylcholine. By treatment with neuraminidase for 4 hr, about 40 mumol/100 mg wer wt of sialic acid was released from taenia coli. This corresponded to two-fifths of total content of sialic acid. By treatment with phospholipase C for 2 hr, a similar amount of sialic acid to that produced by neuraminidase treatment was released. The Scarchard plot of Ca++-binding was a biphasic pattern indicating the presence of two types ofthe Ca++ -binding site with different affinity constants. Neuraminidase produced a 57% decrease in the amount of bound Ca++. The Scatchard plot of Ca++ -binding changed to a monophasic pattern indicating the disapperance of thel ow affinity Ca++ -binding site. Phospholipase C caused a 59% decrease of bound Ca++. The Scatchard plot also indicated the disappearance of the low affinity Ca++ -binding site. From these results, we speculated that sialicacid residue of surface membrane of the muscle cell was first site in the Ca++ -influx mechanism.
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PMID:Changes in contractility and calcium binding of guinea pig taenia coli by treatment with enzymes which hydrolyze sialic acid. 0 22

Neuraminidase [sialidase, EC 3.2.1.18] was found to be widely distributed in bacteria belonging to Arthrobacter. Among these bacteria, Arthrobacter ureafaciens, A. oxydans, and A. aurescens produced relatively potent neuraminidase activities. For the production of this enzyme, not only colominic acid, a homopolymer of N-acetylneuraminic acid, but also N-acetylneuraminic acid, the reaction product of this enzyme, are effective as sources of carbon. An affinity adsorbent specific for neuraminidase was prepared by cross-linking colominic acid with soluble starch by means of epichlorohydrin. Neuraminidase from A. ureafaciens could be purified on this affinity column. The purified neuraminidase was shown to be free from protease, N-acetylneuraminic acid aldolase, phospholipase C, and glycosidases. Aminoff's assay procedure for sialic acid was modified to avoid the centrifugation step. The modified procedure gave a higher molecular extinction coefficient.
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PMID:Distribution of neuraminidase in Arthrobacter and its purification by affinity chromatography. 59 9

Insulin, a mitogen for cultured chick embryo fibroblasts (Temin, H.M. (1968) Cancer 3, 771-787), has been employed to characterize the effects of mitogen/cell membrane interactions as it relates to growth. The specific binding of 125I-insulin to substratum-attached cells is time- and temperature dependent and is optimum at a pH of 7.0. Fetal calf and chicken sera, somatomedin "A/C mixed," and desalanine or native porcine insulin compete with 125I-insulin for membrane-binding sites. Proinsulin, although competing less effectively than native insulin for binding, is more effective than desoctapeptide insulin. Unrelated polypeptide hormones do not compete for 125I-insulin binding. The lowest concentration of insulin at which specific binding is detected is 0.1 nM. Scatchard plot analysis of the binding data indicates that there are two types of binding sites in confluent cultures of fibroblasts: one of high affinity (K1 = 2 to 6 X 10(8) M-1) and low capacity, the other of low affinity (K2 = 0.8 to 3.0 X 10(7) M-1) and high capacity. Approximately 1.9 and 7.1 X 10(3) molecules of insulin are bound at each site, respectively. A 10-min incubation at 24 degrees of the fibroblasts with 10 mug/ml of trypsin causes a 2-fold stimulation of specific 125I-insulin binding and a similar 2-fold increase in insulin-stimulated 2-deoxy-D-glucose uptake and thymidine incorporation. Neuraminidase treatment also produces a 37% increase in specific 125I-insulin binding but treatment with alpha-chymotrypsin or phospholipase C are without significant effect. The results of this and additional experiments support the hypothesis that trypsin treatment of chick embryo fibroblasts leads to an unmasking of 125I-insulin binding sites. Serum starvation of fibroblasts for 12 or 24 h produces a 2.5- to 5-fold increase in specific 125I-insulin binding. This increase is the result of an increase in the number of hormone-binding sites from 9 X 10(3) to 6 X 10(4) per cell which are predominantly of the low affinity type. There is no change in the affinity constants. The presence of camptothecin, or cordycepin, or cycloheximide in the incubation medium completely blocks the increase in number of 125I-insulin-binding sites resulting from serum starvation. The addition of native insulin to the medium of serum-starved cultures also blocks this increase. The magnitude of insulin-stimulated 2-deoxy-D-glucose uptake and thymidine incorporation correlates with the levels of occupancy of the low affinity 125I-insulin-binding sites in untreated fibroblasts. In fibroblasts cultured in the absence of serum, the marked increase in insulin-stimulated 2-deoxy-D-glucose uptake and thymidine incorporation parallels the increase in number of mitogen receptors. The concentration of insulin that produces a half-maximum stimulation of thymidine incorporation is calculated to be 5 X 10(-8) M. At this concentration of insulin, 42% of the receptor sites are occupied.
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PMID:Mitogen receptors in chick embryo fibroblasts. Kinetics, specificity, unmasking, and synthesis of 125I-insulin binding sites. 98 22

Inside-out vesicles were obtained from the cell membranes of murine neuroblastoma. The surface charge of vesicles was studied by the microelectrophoresis method. At neutral pH they had the electrophoretic mobility 2.7 times less than right-side-out vesicles. Neuraminidase treatment reduced the mobility of right-side-out vesicles, while that of inside-out was unchanged. Treatment with trypsin resulted in a decrease of the mobility of both types of vesicles. Treatment with phospholipase C decreased the mobility of inside-out vesicles, but did not influence that of right-side-out ones. Treatment with phospholipase D increased the mobility of both types of vesicles. In the low pH solution the mobility of inside-out vesicles decreased with respect to titration of acidic groups with intrinsic pK 3.5. The mobility of inside-out vesicles depended on Ca2+ concentration.
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PMID:[Surface charge of the cytoplasmic side of the cell membrane of neuroblastoma in murine line C1300]. 321 Dec 25

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

Prostaglandin E2 (PGE2) seems to stimulate cAMP accumulation in ovaries of all mammals. While it acts through specific receptors in some species, our earlier observations (1) suggest absence of PGE2 receptors in the rat ovary. In order to further substantiate this assumption we digested ovarian membranes from the bovine and the rat with various enzymes and measured cAMP after stimulation with PGE2, NaF, and hCG. Pronase, trypsin, and phospholipase C abolished cAMP accumulation completely. Neuraminidase, beta-galactosidase and phospholipase D did not interfere with cAMP formation. After treatment with phospholipase A2, PGE2-mediated cAMP accumulation was abolished in the bovine but not in the rat ovary. Formation of cAMP disappeared after hCG but not after NaF in both species. Furthermore specific binding of PGE2 could not be demonstrated in phospholipase A2-treated bovine ovaries. These findings are consistent with presence of specific PGE2 receptors in the bovine and their absence in the rat ovary.
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PMID:Further evidence for lack of specific receptors for PGE2 in the rat ovary. 614 70

The rat bladder epithelial cell receptors involved in mannose-sensitive adherence of Escherichia coli strains were studied. Sodium metaperiodate and lipase pretreatment of epithelial cells significantly reduced bacterial adherence to cells whereas trypsin and phospholipase C had a marginal or insignificant effect on adherence. Neuraminidase and colominic acid significantly increased adherence, whereas N-acetylneuraminic acid significantly reduced adherence. These data suggest that the rat bladder epithelial cell receptors involved in mannose-sensitive adherence are glycolipids. In addition, the data suggested that sialic acid on bladder epithelial cells acts as a nonspecific inhibitor of adherence, whereas colominic acid, a component of some E. coli K1 capsules, may act as a promoter of adherence.
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PMID:Evidence for a bladder cell glycolipid receptor for Escherichia coli and the effect of neuraminic acid and colominic acid on adherence. 627 93

Bovine leukaemia virus (BLV) was found to agglutinate mouse erythrocytes. Under optimal conditions, including the use of neuraminidase-treated erythrocytes, 200 microgram/ml of BLV purified from the supernatant fluid of BLV-infected bat cells had haemagglutinating titres of about 512 units. BLV haemagglutination was drastically affected by pH and temperature; maximum agglutination occurred at pH 6 and 4 degrees C. That the BLV haemagglutinin is a glycoprotein was suggested by the fact that trypsin, potassium periodate or neuraminidase, but not lipid solvents or phospholipase C, significantly reduced the haemagglutinating (HA) activity of purified BLV. Furthermore, purified BLV glycoprotein of mol. wt. 51 000 (gp51) had HA activity. The receptors for BLV on mouse erythrocytes were inactivated by proteolytic enzymes but not by sodium deoxycholate or potassium periodate. Neuraminidase treatment of erythrocytes increase their agglutinability fourfold. Haemagglutination is a relatively sensitive test for detecting BLV glycoprotein because 0.4 microgram/ml of glycoprotein can be detected by this method. The pH and temperature sensitivity of the BLV HA reaction and specificity for mouse erythrocytes distinguish BLV from that of equine infectious anaemia virus and murine leukaemia virus, the other C type retroviruses known to have HA activity.
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PMID:Haemagglutination by bovine leukaemia virus. 627 77

The properties of adult rhesus monkey testicular FSH receptor was investigated in these experiments. The interaction of 125I-labeled human FSH with a monkey testicular particulate fraction is a time- and temperature dependent phenomenon. Equilibrium of hormone-receptor interaction occurred by about 4-6 at 37 or 34 C, was slow at 25 C, and was extremely slow at 4 C. Maximum binding occurred at pH 7-7.5, with a requirement of 5-10 mM MgCl2 or CaCl2. The half-life of the receptor with exposed sites for hormone interaction was temperature related (1 h at 37 C, 1.5 h at 34 C, 6 h at 25 C, and 36 h at 4 C). Occupancy of these sites by the labeled hormone rendered the receptor more stable. The hormone-receptor complex was highly stable, as shown by the fact that excess unlabeled hormone was unable to displace the already bound labeled hormone from the receptor. Conditions unfavorable for hormone-receptor interaction, such as pH 5.0 or pH 10 or high salt concentration (0.5 M MgCl2), induced the maximum dissociation of the preformed hormone-receptor complex. The primate testis FSH receptor was inactivated by trypsin, phospholipase C, and reducing agents, but it was not influenced by nucleases. Neuraminidase treatment of the particulate receptor may have enhanced its ability to bind labeled human FSH.
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PMID:Studies on primate gonadotropin receptors: characterization of the rhesus monkey testicular follicle-stimulating hormone receptors. 629 May 23

Electron spin resonance (ESR) and the spin label method, with 5-doxyl stearic acid as a probe, were used to investigate the structure of microvillus membrane (MVM) from small intestine of adult and newborn rats. It was shown that the spin label in MVM of newborn was maintained in a more disordered environment than the spin label in adult animals. Calcium ion was used as an external stimulus to study the structural response and organization of these two membrane preparations. Ca++ enhanced the order of 5-doxyl stearic acid labeled MVM from mature and immature rats in a concentration-dependent saturable process, but Ca++ exerted a greater ordering effect on MVM from immature than MVM from the mature rat. Ca++ binding to MVM was also a concentration-dependent, saturable process. MVM from immature rat bound significantly more Ca++ in CaCl2 concentration ranges from 12.5 micron to 4mM. Scatchard analysis of the binding data showed two classes of binding sites with a high affinity constant of 3.1 X 10(4) M-1 and a low affinity constant of 9.1 X 10(3) M-1, with corresponding maximum binding capacities for each class site of 129.8 nmole of calcium/mg protein and 252.7 nmole calcium/mg of protein in newborn and 13-day-old MVM. Only one high affinity constant of 2.6 X 10(4)M-1 with a corresponding maximum binding capacity of 106.4 nmole/mg of protein was observed in adult MVM. Proteolytic hydrolysis of the membranes by trypsin produced an increase in Ca++ binding in adult MVM and a decrease in Ca++ binding in newborn MVM. Neuraminidase and phospholipase C reduced the amount of bound Ca++ in both adult and newborn MVM. These results indicate a more disordered structure of newborn MVM and a differential effect of Ca++ on MVM during development.
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PMID:Development of the gastrointestinal mucosal barrier V. Comparative effect of calcium binding on microvillus membrane structure in newborn and adult rats. 631 42


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