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 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

The conditions necessary for the secretion of phospholipase C (phosphatidylcholine cholinephosphohydrolase) by Pseudomonas aeruginosa were studied. Enzyme secretion by washed cell suspensions required a carbon source and ammonium, potassium, and calcium ions. The calcium requirement could be substituted by magnesium and strontium but not by copper, manganese, cobalt, or zinc. During growth in liquid medium, cells secreted phospholipase C during late logarithmic and early stationary phases. Secretion was repressed by the addition of inorganic phosphate but not by organic phosphates, glucose, or sodium succinate. Studies with tetracycline indicated that de novo protein synthesis was necessary for the secretion of phospholipase C and that the exoenzyme was not released from a preformed periplasmic pool. Similarly, extraction of actively secreting cells with 0.2 M MgCl2 at pH 8.4 solubilized large quantities of the periplasmic enzyme alkaline phosphatase but insignificant amounts of phospholipase C. Bacteria continued to secrete enzyme for nearly 45 min after the addition of inorganic phosphate or rifampin.
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PMID:Secretion of phospholipase C by Pseudomonas aeruginosa. 11 87

1. The requirement for specific polar head groups of phospholipids for activity of purified (Na+ + K+)ATPase from rabbit kidney outer medulla has been investigated. 2. Comparison of content and composition of phospholipids in microsomes and the purified enzyme indicates that purification leads to an increase in the phospholipid/protein ratio and in phosphatidylserine content. 3. The purified preparation contains 267 molecules phospholipid per molecule (Na+ + K+)-ATPase, viz. 95 phosphatidylcholine, 74 phosphatidylethanolamine, 48 spingomyelin, 35 phosphatidylserine and 15 phosphatidylinositol. 4. Complete conversion of phosphatidylserine into phosphatidylethanolamine by the enzyme phosphatidylserine decarboxylase has no effect on the (Na+ + K+)-ATPase activity of the purified preparation. 5. Complete hydrolysis of phosphatidylinositol by a phospholipase C from Staphylococcus aureus, which is specific for this phospholipid, has no effect on the (Na+ + K+)-ATPase activity. 6. Hydrolysis of 95% of the phosphatidylcholine and 60--70% of the spingomyelin and phosphatidylethanolamine by another phospholipase C (Clostridium welchii) lowers the (Na+ + K+)-ATPase activity by about 20%. 7. Combination of the phospholipid-converting enzymes has the same effect as can be calculated from the effects of the enzymes separately. Only complete conversion of both phosphatidylserine and phosphatidylinositol results in a loss of 44% of the (NA+ + K+)-ATPase activity and 36% of the potassium 4-nitrophenylphosphatase activity. 8. These experiments indicate that there is no absolute requirement for one of the polar head groups, although in the absence of negative charges the activity is lower than in their presence.
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PMID:Role of negatively charged phospholipids in highly purified (Na+ + K+)-ATPase from rabbit kidney outer medulla studies on (Na+ + K+)-activated ATPase, XXXIX. 14 6

Colloidal alpha-stannic acid and a negative iron colloid obtained from ferric hydroxide and potassium ferrocyanide, both negative sols being stable within a wide pH range, were refined as surface protein electron markers. Because of the relatively small size of its particles, colloidal alpha-stannic acid was used for staining all surface proteins. According to the pH at which the negative iron colloid was applied, it revealed either all surface proteins, or because of its large colloidal particles, stained basic proteins. This differential staining capability of the iron colloidal has been demonstrated previously on various control preparations (Puvion E, Blanquet PR: J Microsc 12:171, 1971). Controls on the affinity of the two colloids to surface amino groups were carried out on rat liver, mouse fibroblasts, HeLa and KB cells, Ehrlich and Zajdela ascites cells subjected to prior enzymatic and chemical treatments (incubation with neuraminidase or phospholipase C, esterification, acetylation or lipid extraction). At any pH below 9, the two sols stained proteins in the outer hydrophilic leaflet of esterified cells with relative selectivity, but the alpha-stannic acid showed them more accurately. The iron sol did reveal at high pH protein components of high isoionic point on the surfaces of rat hepatocytes and ascites cells which had only been treated with neuraminidase.
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PMID:Colloidal alpha-stannic acid and negative iron colloid as differential electron stains for surface proteins. 23 40

Dopamine receptors of D2 type present on lactotroph cells are coupled to a large series of transduction mechanisms. Beside their negative coupling with adenylate cyclase, they are also coupled with potassium and calcium channels, leading to a decreased intracellular calcium concentration. In addition, D2 dopamine receptors also modulate phospholipase activities. Dopamine inhibits inositol phosphate production, through two distinct mechanisms. One of them could represent a direct negative coupling with phospholipase C. All these transduction mechanisms of the D2 dopamine receptors implicate G proteins sensitive to pertussis toxin. In contrast, these receptors are negatively coupled to phospholipase A2 through G proteins insensitive to this toxin. Both isoforms of the D2 dopamine receptor, generated by alternate splicing of a single gene, are present in lactotroph cells. After transfection in CH4C1 cells the two isoforms are coupled with adenylate cyclase while only the shortest isoform appears negatively coupled to phospholipase C. Functional D2 dopamine receptors are present in human prolactinomas. Resistance to bromocriptine therapy is associated with a decreased density of these receptors in the tumor. In addition, the ratio of the two receptor isoforms (measured by PCR) is different in responsive and resistant tumors. Furthermore, the activity of Gi/Go proteins coupled to adenylate cyclase appears also affected in resistant tumors. Resistance to bromocriptine therapy appears thus to involve multiple changes at the different levels of the multiple mechanisms of action of dopamine on lactotroph cells.
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PMID:D2 dopaminergic receptors: normal and abnormal transduction mechanisms. 130 22

The heterotrimeric guanine nucleotide binding proteins (G proteins) are activated by sensory or hormone receptors. In turn, the G proteins activate effector proteins such as adenylyl cyclase, cyclic guanosine 3',5'-monophosphate phosphodiesterase (cGMP PDE), phospholipase C, and potassium and calcium ion channels by mechanisms that are poorly understood. A site on the alpha subunit of the G protein transducin (alpha t) has been identified that interacts with and activates cGMP phosphodiesterase, the effector enzyme in rod photoreceptors. A 22-amino acid peptide, corresponding to residues 293 to 314 from the COOH-terminal region of alpha t, fully mimicked alpha t and potently activated PDE. This region is adjacent to the receptor activation domain; thus, the alpha subunit of this G protein has a site for interaction with both its effector and receptor that maps near the COOH-terminus.
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PMID:A site on rod G protein alpha subunit that mediates effector activation. 131 58

In the kidney, adenosine plays important regulatory roles, including renal blood flow, glomerular filtration rate, renin secretion, tubuloglomerular feedback, tubular reabsorption of sodium and water, sympathetic neurotransmitter release, and erythropoietin secretion. These functions are mediated through adenosine 1 (A1)-receptors and adenosine 2 (A2)-receptors. These receptors couple to the inhibition and stimulation of adenylate cyclase, through Gi and Gs proteins, respectively. A variety of other effecter systems have been reported to be coupled to A1 receptors, including phospholipase C, phospholipase A2 and potassium, as well as Ca++ channels. Recently, A1 receptors, A2 receptors and novel A2 receptor have been cloned, sequenced and expressed. In association with the development of selective adenosine analogues, we are now ready to take up problems at the biochemical and molecular biological levels.
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PMID:[Adenosine and adenosine receptors in the kidney]. 149 49

S. aureus alpha-toxin and E. coli hemolysin (Hly) represent two prototypes of pore-forming cytolysins. Both are established virulence factors and have been implicated in the development of septic lung failure. Low doses of these agents cause thromboxane-mediated vasoconstriction and edema formation in isolated perfused rabbit lungs. In a preceding investigation, we observed that alpha-toxin causes overt endothelial cell damage in these lungs, as demonstrable by electron microscopy (Seeger W, Birkemeyer RG, Ermert L, Suttorp N, Bhakdi S, Duncker HR: Lab Invest 63:341, 1990). Here, we present results of a parallel study conducted with E. coli hemolysin. Thromboxane-dependent pulmonary hypertension was suppressed by the addition of acetylsalicylic acid to the perfusion fluid in all cases. Administration of 0.2 hemolytic units (HU; i.e., 20 ng/ml protein) resulted in progressive weight gain after a lag period of 10 to 15 minutes, and 30 minutes after toxin application the gravimetrically determined capillary filtration coefficients (Kfc) were increased greater than 10-fold. Perfusion was terminated when the total lung weight gain surpassed 20 gm. 0.12 HU/ml E. coli hemolysin caused 2- to 3-fold increased capillary filtration coefficients values within 110 minutes, concomitant with intermediate quantities of edema formation (9.7 +/- 2.7 gm). Potassium liberation in the absence of lactate dehydrogenase release occurred in all toxin treated lungs. Electron microscopic examination after perfusion fixation revealed interstitial edema formation in areas remote from the blood-gas exchange barrier. Increased numbers of endothelial plasmalemmal vesicles were visualized at the very onset of edema formation in lungs exposed to 0.2 HU/ml, and after a 110-minute exposure to 0.12 HU/ml of the toxin, but not in lungs exhibiting severe edema (greater than 20 gm weight gain). In contrast to our previous results with alpha-toxin, endothelial cells displayed normal electron density here and were not detached from the fused basal lamina. Hence, although both pore formers provoke severe vascular leakage in our experimental model, the underlying pathways probably divert fundamentally from each other.
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PMID:Induction of severe vascular leakage by low doses of Escherichia coli hemolysin in perfused rabbit lungs. 153 89

Interactions between GABAA and GABAB receptors were studied using muscimol-stimulated uptake of 36Cl- by membrane vesicles from mouse cerebellum. Baclofen inhibited muscimol-stimulated 36Cl- uptake and this action was more pronounced with longer flux times (30 vs. 3 s) and after predesensitization of GABAA receptors. Baclofen also inhibited 36Cl- flux by cortical membranes but was more effective with cerebellar preparations. The action of baclofen was stereoselective, calcium-dependent, and blocked by the GABAB receptor antagonist 2-OH-saclofen. It was mimicked by GTP-gamma-S but not by GDP-beta-S, which suggests that baclofen may be acting via a G protein. The action of baclofen was inhibited by U73122, an inhibitor of phospholipase C. However, the potassium channel blockers tetraethylammonium or Ba2+ did not affect the action of baclofen. The results show that activation of GABAB receptors can inhibit the function of GABAA receptors and suggest that this action involves either a nondesensitizing subtype of GABAA receptor or the rate or recycling of desensitized to nondesensitized receptors. We speculate that this action of baclofen results from activation of phospholipase C and phosphorylation of a subtype of GABAA receptor by protein kinase C.
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PMID:Cerebellar GABAB receptors modulate function of GABAA receptors. 164 24

Pseudorabies virus hemagglutinin was readily adsorbed on mouse erythrocytes at 4, 22, or 37 degrees C, but not on cattle erythrocytes. The adsorbed hemagglutinin could not be eluted from the cells by resuspending in phosphate-buffered saline (PBS), by incubating at 37 or 50 degrees C, or by incubating in the presence of neuraminidase. The receptor on mouse erythrocytes for the hemagglutinin was inactivated by trypsin, but not by neuraminidase, sodium deoxycholate (DOC), potassium periodate (KIO4), dithiothreitol (DTT), 2-mercaptoethanol (2-ME) and formalin. The hemagglutinin was inactivated by trypsin, alpha-amylase, pepsin, DOC, KIO4, and ethylendiamine-tetraacetic acid (EDTA), but not by papain, beta-glucosidase, phospholipase C, neuraminidase, DTT, 2-ME, Tween-80, ethylether, chloroform, trichloro-trifluoroethane, beta-propiolactone and formalin, suggesting that the hemagglutinin active component involved glycoproteins. The hemagglutinin was stable at 37 degrees C for lower temperatures but not at 60 degrees C or higher. The hemagglutinin activity was resistant to ultraviolet irradiation, while the infectivity was very susceptible. The hemagglutinin and the infectivity were readily sedimented by ultracentrifugation at 48,000 x g for 3 hr. In rate zonal centrifugation of the preparation on a sucrose density gradient, the hemagglutination (HA) activity showed a sharp peak at 1.22 g/ml coinciding with the peak of infectivity. The HA activity in the peak fraction seemed to be structually associated with virus particles. After fractionation of the virus by Nonidet P-40, the HA activity was found only in the fraction of the envelope material, indicating that the hemagglutinin is situated in the viral envelop.
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PMID:Physicochemical properties of pseudorabies virus hemagglutinin. 166 85


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