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:3.1.3.1 (alkaline phosphatase)
47,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The action of ATP on Ca(2+)-dependent K+ channels was studied in fresh human erythrocytes using patch-clamp techniques. Single-channel current was recorded at pH 6.5 from inside-out patches in the presence of symmetrical K+ gluconate solutions, containing both 1 microM free Ca2+ in the bath and 0.5 mM LaCl3 on the pipette side. With no ATP, the electrical activity revealed low-conductance K+ channels (25 pS), which showed inward rectification and an opening kinetics dependent on membrane potential. When ATP (1 mM) and Mg2+ (2 mM) were added together and a depolarizing potential was simultaneously applied, only a high-conductance channel (about 75 pS) was observed. This channel showed no rectifying properties and it was not found if ATP was added in the absence of Mg2+. Channel activity was enhanced by adding fluoride (10 mM) or trifluoperazine (50 microM) whilst it was reduced after incubating with dibutyryl cAMP (50 microM) or alkaline phosphatase (250 U/ml). On the other hand, when fragmented membranes from inside-out vesicles were incubated with gamma-32 P-ATP and 1 microM free Ca2+ under above conditions, only two high-molecular weight polypeptides (235 and 320 kDa) were labelled with 32P. The results suggest that ATP-mediated phosphorylation of Ca(2+)-dependent K+ channels leads to a high-conductance state.
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PMID:The effect of ATP on Ca(2+)-dependent K+ channels of human red cells. 130 89

An in vitro model to study the molecular control of binding of highly purified synaptic vesicles to presynaptic plasma membranes has been developed. Presynaptic plasma membranes were immobilized by dotting onto nitrocellulose, and binding of iodinated synaptic vesicle membranes was studied under varying experimental conditions. Synaptic vesicles bind to presynaptic plasma membranes in the presence of Ca2+ and ATP. Binding is reduced in the presence of EGTA and abolished by the calmodulin antagonist trifluoperazine. Vesicle binding is stimulated 5-fold after incubation--prior to dotting--of presynaptic plasma membranes with ATP in the presence of the phorbol-ester 12-O-tetradecanoylphorbol-13-acetate (1 microM) and 2.5-fold after preincubation with Ca2+ (50 microM). Pretreatment of plasma membranes with alkaline phosphatase strongly reduces vesicle binding. Microsomes prepared from bovine liver did not bind to presynaptic plasma membranes. Our results suggest that activation of protein kinase C and Ca2+ stimulate binding of synaptic vesicles to the presynaptic membrane. In the intact nerve terminal this interaction may represent an initial step in synaptic vesicle exocytosis.
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PMID:In vitro binding of isolated synaptic vesicles to presynaptic plasma membranes: activation by Ca2+ and protein kinase C. 130 19

Partial liver transplantation from living donors is a new surgical operation on patients in the final stage of liver dysfunction. Among about 90 operations so far done in the world, 34 were performed at the Second Department of Surgery in Kyoto University Hospital (as of June, 1992). Good but limited cooperation between surgeons and clinical laboratories has contributed to saving the lives of as many as 28 patients. Analysis of laboratory data and clinical course of patients indicated that pre-, mid-, and postoperational examinations of blood flow through the graft liver by the use of Doppler echography and the monitoring of the liver capacity to generate ATP by the aid of the arterial ketone body ratio are most important for early detection of dysfunctioning liver grafts. An unusually high incidence of the transient hyperphosphatasemia-like elevation of alkaline phosphatase and a frequent appearance of liver-type arginase in serum during the postoperative stage seemed to indicate some pathological changes of the liver.
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PMID:[Liver transplantation and functions of the graft liver]. 130 20

Regulation of Cl conductance by protein kinase A may play a role in control of endosomal acidification [Bae, H.-R., & Verkman, A. S. (1990) Nature, 348, 637-639]. To investigate the mechanism of kinase A action, cell-free measurements of Cl transport and membrane protein phosphorylation were carried out in apical endocytic vesicles from rabbit kidney proximal tubule. Cl transport was measured by a stopped-flow quenching assay in endosomes labeled in vivo with the fluorescent Cl indicator 6-methoxy-N-(3-sulfopropyl)quinolinium. Phosphorylation was studied in a purified endosomal preparation by SDS-PAGE and autoradiography of membrane proteins labeled by [gamma-32P]ATP. Endosomes had a permeability (PCl) for conductive Cl transport of 3.1 x 10(-8) cm/s at 23 degrees C which was stilbene inhibitable. PCl was increased by 90 +/- 20% by a 10-min preincubation with the catalytic subunit of kinase A (PKA, 10 units/mL) and MgATP (0.5 mM) with anion selectivity Cl greater than I greater than Br. The increase in PCl was blocked by 100 microM N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide (H-8) and was reversed by addition of alkaline phosphatase (AP, 40 units/mL) after incubation with PKA and MgATP; the increase in PCl was not blocked by pretreatment with AP.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Protein kinase A dependent membrane protein phosphorylation and chloride conductance in endosomal vesicles from kidney cortex. 131 27

We studied the effect of bromolevamisole (BL) and other imidazo [2,1-b] thiazole derivatives--bromodexamisole (BD) and levamisole (LV)--on adenylate cyclase (AC) activity. BL and BD both inhibited forskolin-activated human thyroid AC, while LV had no effect. This inhibition was non-stereospecific and the IC50 values, as measured with 1 mM ATP and 40 microM forskolin, were 0.95 and 0.80 mM for BL and BD, respectively. In contrast, human thyroid alkaline phosphatase (ALP) inhibition was stereospecific, with IC50 values of 0.0012 mM for BL and 0.9 mM for BD. LV was a 10-fold weaker inhibitor of ALP than BL. These results show that ALP inhibition is not correlated with forskolin-activated AC inhibition. Furthermore, in the presence of a competitive inhibitor of GTP (0.1 mM guanosine 5'-O-(2-thiodiphosphate), BL retained its antagonizing effect on forskolin-activated AC which suggests a direct action on the catalytic subunit. The inhibition was of the mixed type, indicating a complex interaction between BL and AC. Glucagon-activated AC activity in rat liver membranes was also inhibited by BL, although to a slightly lesser degree than thyroid stimulating hormone (TSH)-activated AC from human thyroid for a given BL concentration. In cultured human thyroid cells, BL (0.25 mM) induced a potent decrease in cAMP accumulation after 2 hr of stimulation by TSH. Taken together, these results show that BL inhibits AC and that this inhibition is not organ-specific.
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PMID:Effect of bromolevamisole and other imidazo [2,1-b] thiazole derivatives on adenylate cyclase activity. 131 3

IL-8 is a neutrophil-specific chemoattractant and cellular activator which exists in at least three forms, 69, 72, and 77 amino acids. The predominant monocyte product has 72 amino acids, whereas endothelial cells secrete the 77-amino acid form. The 72-amino acid form has been shown to increase intracellular calcium in neutrophils, but the exact biochemical pathways involved in stimulation of these cells is unknown. N-formyl peptide chemoattractants in neutrophils stimulate the formation of phosphatidylinositol-4,5-bisphosphate (PIP2), a reservoir for second messenger molecules and regulator of actin assembly through its association with the actin-binding proteins, profilin, and gelsolin. The present study examined whether IL-8 altered the enzyme which synthesizes PIP2, phosphatidylinositol-4-phosphate (PIP) kinase. Incubation of intact neutrophils with 10 nM IL-8 caused approximately a twofold increase in the activity of the enzyme. All forms of IL-8 stimulated PIP kinase activity in concentrations ranging from 1 to 50 nM, and the dose-response curves exactly correlated with the order of potency of these cytokines for interacting with the IL-8R on the surface of neutrophils. Lineweaver-Burk analysis of the kinetics of PIP kinase assayed in the presence of 0.03 to 0.7 mM ATP showed that 10 nM IL-8 increased the Vmax of the enzyme 38 to 70.5%, with no significant change in the apparent Km for ATP or for PIP. The stimulation of PIP kinase activity could not be explained by decreased degradation of PIP2 by phospholipase C or phosphomonoesterase activity in the membranes isolated from cells treated with IL-8 or by a decrease in the degradation of ATP. The microfilament disrupter, cytochalasin b, inhibited IL-8 induced stimulation of PIP kinase. These findings demonstrate that all forms of IL-8 stimulate PIP kinase in human neutrophils. This event may provide molecular signals to these cells that are necessary to maintain or change the state of microfilament assembly during cellular activation.
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PMID:IL-8 stimulates phosphatidylinositol-4-phosphate kinase in human polymorphonuclear leukocytes. 131 31

The role of the calcium pump in the stimulation of intestinal calcium transport activity by 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25(OH)2D3] was examined in chicks. The in situ intestinal absorption of calcium increased approximately threefold in the duodenum, jejunum, and ileum 6 h after a single injection of 625 ng of 1 alpha,25(OH)2D3 into vitamin D-deficient chicks. The same treatment also increased approximately twofold the rate of ATP-dependent calcium uptake by the basolateral membrane vesicles (BL) isolated from those three sites. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that a Mg(2+)-dependent calcium-stimulated phosphorylated intermediate with an apparent molecular mass of 105 kDa appeared in the BL. The 1 alpha,25(OH)2D3 treatment gave no change in the levels of the intermediate. Pretreatment of the BL with alkaline phosphatase decreased the calcium uptake by the BL isolated from 1 alpha,25(OH)2D3-treated chicks, but it had little effect on the uptake by the BL from vitamin D-deficient chicks. These results suggest that at an early stage of the 1 alpha,25(OH)2D3-induced intestinal calcium transport process, the vitamin regulates the calcium-pumping activity of chick intestinal BL by phosphorylation and dephosphorylation but not by a stoichiometric change in the pump.
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PMID:Mechanism of regulation of calcium-pumping activity in chick intestine. 131 10

Lymphocytes infected in vivo with HIV or lymphoblastoid cells exposed in vitro to either HIV or its envelope glycoprotein (gp120) show a defect in inositol polyphosphate-mediated signal transduction together with an associated abnormality in intracellular calcium regulation. The defect in patients reverses after treatment with the anti-retroviral agent zidovudine (AZT). We present evidence that the defect is at the level of the Ins (1,3,4,5)P4 5-phosphomonoesterase (PME) in these cells and that, though elevation of the intracellular ATP level partially down-regulates the activity of this enzyme, such changes alone are unable to account for the complete inhibition seen in HIV-infected cells.
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PMID:The defect seen in the phosphatidylinositol hydrolysis pathway in HIV-infected lymphocytes and lymphoblastoid cells is due to inhibition of the inositol 1,4,5-trisphosphate 1,3,4,5-tetrakisphosphate 5-phosphomonoesterase. 132 Oct 14

Renal epithelial function, proton flux and sodium stimulated proton flux, was observed in vesicles isolated from the brush border of the proximal tubule of Sockeye Salmon (Oncorhynchus nerka) during migration. Brush border membrane vesicles (BBMV) were isolated from the body kidney of Sockeye Salmon using aggregation/differential centrifugation techniques. Vesicle purity was tested using a series of epithelial and basal lateral markers including alkaline phosphatase, maltase, gamma-glutamyl transferase (GGTP), Mg(2+)-activated ATP-ase, Na(+)+K(+)-activated ATPase, and 5'-nucleotidase and the lysosomal marker acid phosphatase. An enrichment/depletion factor for each marker was determined by comparison of purified BBMV with kidney homogenate. Vesicles exhibit an enrichment factor for alkaline phosphatase, GGTP, maltase, Mg(2+)-activated ATP-ase, Na(+)+K(+)-activated ATPase, and 5'-nucleotidase. A depletion factor was observed for acid phosphatase. Vesicle integrity was tested by measuring the time course of proton flux in the presence of a pH gradient. Amiloride sensitive sodium stimulated proton flux was observed in these vesicles. The presence of sodium caused a saturable increase in the rate of proton flux, indicating the activity of a sodium/proton antiport protein in BBMV.
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PMID:Proton transport and Na+/H+ exchange in vesicles isolated from sockeye salmon (Oncorhynchus nerka) kidneys during migration from salt to fresh water. 132 4

1. Two distinct patterns of Ca(2+)-mediated activation of Ca(2+)-ATPase were identified in calmodulin-depleted membranes. 2. In membranes showing no activation (type A), preincubation with micromolar concentration of cyclic AMP and ATP made possible stimulation of the enzyme while in membranes already exhibiting activation (type B), preincubation with cyclic AMP and ATP abolished the activation. 3. ATPase stimulation in type A membranes was suppressible by leupeptin. 4. Triton extractable inhibitor isolated from type A membranes was as active as that derived from type B membranes only after preincubating the membranes with cyclic AMP and ATP. 5. The inhibitor could be inactivated by alkaline phosphatase.
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PMID:Variations in Ca(2+)-mediated activation of Ca(2+)-ATPase and its associated inhibitor in erythrocyte membrane. 132 91


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