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 responsiveness of human dental pulp (HDP) cells to parathyroid hormone (PTH) was investigated by measuring their cyclic AMP (cAMP) content, DNA synthesis, alkaline phosphatase activity, collagen synthesis, and glycosaminoglycan (GAG) synthesis. PTH dose-dependently increased the intracellular cAMP 1 min after the addition of PTH. Confluent HDP cells on day 14 expressed a high level of cAMP production after addition of 3 units/ml PTH. The hormone did not affect DNA synthesis by HDP cells. Alkaline phosphatase activity was suppressed by PTH to 81% of control (p < 0.01), and addition of dibutyryl cAMP to the medium mimicked the effect of PTH (79% of control, p < 0.01). The hormone inhibited collagen synthesis (15% decrease of [3H] proline incorporation, p < 0.01), and stimulated non-collagen protein synthesis (10% increase, p < 0.05). The increase of non-collagen protein by PTH was in accordance with the enhancement of GAG synthesis (17% increase of [35S]sulfate incorporation, p < 0.01). Dibutyryl cAMP caused further increase of GAG synthesis, to 155% of control (p < 0.01). Observations of the radiolabeled proteins on 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis after metabolic labeling with [14C]proline and [35S]sulfate revealed a similar tendency to the quantitative determinations in which PTH inhibited collagen synthesis and stimulated GAG synthesis. These findings suggest that HDP cells have some osteoblastic characteristics in terms of PTH responsiveness, and that this culture system is a useful model for studies of human dental pulp.
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PMID:Actions of parathyroid hormone on cultured human dental pulp cells. 133 58

The effects of prostaglandin E 2 (PGE2) on the differentiation and proliferation of osteoblasts (human fetal bone-cells) cultured in serum-free medium were investigated by assays of alkaline phosphatase (ALP) activity, intracellular cyclic AMP level and collagen synthesis in the cells. The results suggested that PGE2 in physiologic concentration stimulated the differentiation of osteoblasts in vitro, and might be involved in bone formation in vivo.
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PMID:[Effects of prostaglandin E2 on growth and function of osteoblasts in human cell culture in vitro]. 133 4

1. The inward current and the M-current (IM) suppression produced when muscarine is applied to frog sympathetic ganglion cells was recorded by means of the whole-cell patch-clamp technique. The holding potential was -30 mV and [K+]o was 6 mM. 2. The steady-state IM was maintained for at least 20 min when the patch pipette contained neither adenosine 5'-triphosphate (ATP) nor adenosine 3':5'-cyclic monophosphate (cyclic AMP). Inclusion of these substances or the ATP antagonist, beta,gamma-methyleneadenosine 5'-triphosphate (beta,gamma-MethATP; 1 or 2 nM) (failed to alter the rate of IM 'run down'. By contrast, inclusion of adenosine-5'-O-(3-thiotriphosphate) (ATP-gamma-S, 1 or 2 mM) resulted in a 60% reduction of the current within 18 min. 3. Despite the inability of ATP-gamma-S to maintain steady-state IM, it had no effect on the ability of muscarine (2-100 microM) to suppress a constant fraction of the available current. ATP-gamma-S and beta,gamma-MethATP increased the rise time and duration of the response to muscarine. 4. Inclusion of a phosphatase inhibitor, diphosphoglyceric acid (DPG, 1-2.5 mM) or alkaline phosphatase (100 micrograms ml-1) failed to affect the amplitude of muscarinic responses. 5. These results question the role of the phosphorylation and/or dephosphorylation reactions in the transduction mechanism for muscarine-induced IM suppression but are consistent with the possibility that M-channels are 'directly coupled' via G-protein to the muscarinic receptor.
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PMID:M-currents in frog sympathetic ganglion cells: manipulation of membrane phosphorylation. 137 98

1. Effect of intracellular ATP on Cl- current (ICl) mediated by the GABA (gamma-aminobutyric acid) receptor subtype, GABAA, was studied in dissociated nucleus tractus solitarii (NTS) neurones using the whole-cell mode of patch clamp. A concentration-jump technique termed 'Y tube' was used to rapidly apply agents externally. Dissociated neurones were obtained from 1- to 3-week-old rats. 2. When the patch-pipette solution contained 2 mM-ATP, the amplitude of ICl elicited by 10(-5) M-GABA did not show any time-dependent decrease (apparent run-down), for more than 60 min after the initial recording. In the presence of ATP, the half-maximum concentration (KD) and Hill coefficient calculated from the GABA concentration-response curve were 9.12 microM and 1.47, respectively. 3. In the absence of intracellular ATP, the amplitude of GABA-induced ICl decreased with time. The relative peak amplitudes after 20 and 60 min from the initial recording were 0.40 +/- 0.09 (n = 11) and 0.16 +/- 0.05 (n = 8) with respect to the initial response. 4. Removal of Mg2+ from the internal solution induced run-down of the GABA response even in the presence of 2 mM-intracellular ATP, suggesting that both intracellular ATP (2 mM or more) and Mg2+ are necessary to prevent run-down of the GABA response. 5. Activation of dephosphorylation processes by alkaline phosphatase (100-200 microM) did not affect the GABA response in neurones perfused with internal solution containing 2 mM-ATP and 3 mM-Mg2+. Blocking the dephosphorylation process by okadaic acid, a phosphatase inhibitor, did not prevent the run-down of the GABA response. 6. Calcium influxes passing through both the voltage-dependent L-type Ca2+ channel and the glutamate receptor-operated cation channel did not affect ICl induced by GABA. 7. GABA-induced ICl was also maintained by adding 2 mM-ADP or ATP gamma S (adenosine-5'-O-3-thiotriphosphate) to the internal solution containing Mg2+. Addition of 2 mM-adenosine, AMP, cyclic AMP, AMP-PNP (adenylimido-diphosphate) or ADP beta S (adenosine-5'-O-2-thiodiphosphate) to the internal solution did not prevent the run-down of the GABA response even in the presence of 3 mM-intracellular Mg2+. Based on the chemical specificity of these ATP analogues, it is suggested that there is an ATP-sensitive binding site (ATP receptor) in the cytoplasmic side of the cell membrane.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Direct modulation of GABAA receptor by intracellular ATP in dissociated nucleus tractus solitarii neurones of rat. 138 52

A simple procedure, involving heat-treatment, DEAE-Sephadex, AMP-Sepharose and Bio-Gel P-60 chromatography, was developed for the purification of S1 nuclease to homogeneity from commercially available Takadiastase powder. Chemical modification of the amino groups of purified S1 nuclease revealed that lysine is essential for single-stranded DNAase, RNAase and phosphomonoesterase activities associated with the enzyme. The kinetics of inactivation suggested the involvement of a single lysine residue in the active site of the enzyme. Additionally, lysine modification was accompanied by a concomitant loss of all the activities of the enzyme, indicating the presence of a common catalytic site responsible for the hydrolysis of single-stranded DNA, RNA and 3'-AMP. Substrate-protection and inhibitor-binding studies on enzyme modified with 2,4,6-trinitrobenzenesulphonic acid showed that lysine may be involved in the substrate binding.
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PMID:Active-site characterization of S1 nuclease. I. Affinity purification and influence of amino-group modification. 163 40

A prominent galactose-1-phosphatase was isolated from rat brain and partially purified by chromatography on diethylaminoethyl-Sephacel, hydroxylapatite, and Sephacryl S-300 columns. The galactose-1-phosphatase was separated from alkaline phosphatase, and from two forms of glucose-1-phosphatase. The three columns gave a 10-fold increase in specific activity to 290 mol/min/mg of protein, with a yield of 15%. Of the eight sugar phosphates tested, galactose-1-phosphate was the best substrate for the purified enzyme, followed by glucose-1-phosphate, which was hydrolyzed 40% as rapidly as galactose-1-phosphate. Galactose-1-phosphatase had an optimum pH of 8.5 and a Km value of 2.5 mM for galactose-1-phosphate hydrolysis. Mg2+ was required for activity, and supported half-maximal activity at a concentration of 1.25 mM. Phosphate was the only potent inhibitor found ATP, arsenate, and vanadate caused moderate inhibition of 10 mM levels, whereas AMP, L-homoarginine, and L-phenylalanine stimulated enzyme activity. Galactose-1-phosphatase was determined to have a Stokes radius of 30 A and a sedimentation coefficient of 4.1S. These values were used to calculate a molecular weight of 50,200 and a frictional ratio showing the enzyme to be a globular protein. It is hypothesized that a similar phosphatase may play a role in reducing brain galactose-1-phosphate concentrations in patients with galactosemia.
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PMID:Galactose-1-phosphatase in rat brain. 164 51

We hypothesized that retention of parenterally delivered calcium (Ca) and phosphorus (P) is affected by the ratio of the delivered minerals and that a 1.7:1 ratio would be optimal since this is the ratio of retention of these minerals by the fetus. Forty-one very low birth weight (VLBW) infants were randomly assigned to one of three total parenteral nutrition (TPN) solutions that were different only in their Ca:P ratios: 2:1 (76 mg/kg/day Ca and 38 mg/kg/day of P), and 1.3:1 (58 mg/kg/day Ca and 45 mg/kg/day P), and 1.3:1 (58 mg/kg/day of Ca and 45 mg/kg/day of P). Serum levels of calcium, phosphorus, and alkaline phosphatase, retentions of calcium and phosphorus and urinary cyclic AMP levels were measured after 48 h on the assigned Ca to P ratio. Calcium retentions were higher with the 2:1 and 1.7:1 ratios and phosphorus retentions were higher with the 1.3:1 and 1.7:1 ratios. The 1.7:1 ratio allowed for the highest absolute retention of both minerals and was the closest to published in utero accretion of calcium and phosphorus. The serum and urine studies demonstrated no abnormalities on any of the three ratios. Cyclic AMPs were not different among groups and were not elevated compared to previous reports suggesting that none resulted in parathyroid hormone (PTH) stimulation. We conclude that the 1.7:1 ratio is better than higher or lower ratios for delivery of calcium and phosphorus in TPN solutions at the quantities studied.
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PMID:Effect of calcium/phosphorus ratio on mineral retention in parenterally fed premature infants. 164 88

The cellular basis for hormonal control of bone resorption is poorly understood. As the identifiable receptors for bone resorbing agents such as parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] are located on osteoblasts rather than osteoclasts, the nature of cellular signaling is obscure. Here it is reported that exposure of fetal rat limb bones to pertussis toxin, a bacterial protein that inhibits certain GTP binding proteins (G-proteins) involved in signal transduction, markedly inhibits bone resorption elicited by PTH, 1,25(OH)2D3 and prostaglandin E2. Pertussis toxin does not block the inhibition of alkaline phosphatase activity by PTH or 1,25(OH)2D3, and it potentiates the cyclic AMP response to PTH. These data support the existence of a pertussis toxin-sensitive G-protein that participates in regulation of bone resorption. The putative G-protein is apparently not involved in the initial transduction of hormonal signals, but it may be part of a final common pathway through which the osteoclast is activated by agents with widely divergent initial actions.
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PMID:Pertussis toxin inhibits hormonal stimulation of bone resorption in fetal rat limb bones. 165 45

An oral calcium (Ca) tolerance test was used to compare the acute calcaemic, calciuric, parathyroid and bone turnover responses in 21 women at 36 weeks of pregnancy, 27 breast-feeding women studied 22 weeks postpartum and 27 control women. In all groups the oral Ca load increased plasma Ca and urinary calcium excretion (CaE), reduced intact PTH concentration (and consequently reduced renal phosphate and cyclic AMP excretion) and reduced hydroxyproline excretion (HypE, a biochemical index of bone resorption). There were no changes in the biochemical indices of bone formation, serum osteocalcin (elevated in the lactating group) and alkaline phosphatase, in any group. The pregnant women had the same fall in HypE and a greater calcaemic response than the controls. These results suggest that there is increased intestinal Ca absorption efficiency and a normal rate of bone resorption in late pregnancy. In contrast, the lactating women had a greater fall in HypE (from a baseline twice that of controls) and a significantly lower (p less than 0.001) rise in CaE, despite a calcaemic response similar to that of controls. Therefore, in lactation there is increased bone turnover and an increased capacity to reabsorb Ca in the renal tubule, compared to controls. An oral calcium supplement may benefit breast-feeding women, by reducing lactation-related elevated rate of bone resorption and consequent loss of trabecular bone.
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PMID:Acute effects of an oral calcium load in pregnancy and lactation: findings on renal calcium conservation and biochemical indices of bone turnover. 166 6

1. The effects of alkaline phosphatase on platelet aggregation, secretion and thromboxane B2 (TxB2) generation induced by the full dose-range of common platelet agonists were studied in human platelet-rich plasma and washed platelets. 2. Platelet aggregation and adenosine 5'-triphosphate (ATP) secretion induced by threshold and supramaximal concentrations of arachidonate and stable TxA2 and prostaglandin endoperoxide-mimetics (compounds U46619 and EP171) were abolished in the presence of alkaline phosphatase (0.5-1 u ml-1), even though the synthesis of TxB2 persisted. In contrast, platelet aggregation by PAF-acether and by supramaximal concentrations of thrombin as well as the primary wave of aggregation by adenosine diphosphate (ADP) and adrenaline were unaffected by alkaline phosphatase under conditions where the secondary wave of aggregation by ADP was blocked. 3. Alkaline phosphatase, unlike prostacyclin, failed to raise the adenosine 3':5'-cyclic monophosphate (cyclic AMP) content of the platelets. Also, the pretreatment of platelets by inorganic phosphate or by ATP plus creatine phosphate/creatine phosphokinase reversed the inhibitory effect of alkaline phosphatase. 4. Experiments performed in the guinea-pig in vivo showed that alkaline phosphatase was effective on thrombocytopenia induced by arachidonate. 5. Our results provide the first direct evidence for a specific inhibitory effect of alkaline phosphatase at a site sensitive to TxA2 and prostaglandin endoperoxides and suggest that its phosphorylation/dephosphorylation state may play an important role in modulating platelet activation. These results also suggest the presence of ecto-protein kinases on membrane platelets.
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PMID:Alkaline phosphatase prevents platelet stimulation by thromboxane-mimetics. 166 43


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