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)

Cytochemistry revealed that alkaline phosphatase was localized predominantly to the maternal facing plasma membrane of syncytiotrophoblast layer II in the haemotrichorial rat placenta at term. Plasma membrane vesicles prepared from term rat placenta by homogenization, treatment with MgCl2, and differential centrifugation were enriched 14-fold in alkaline phosphatase activity as compared to homogenate. These vesicles were mainly oriented right side out, as shown by a lack of effect of saponin treatment on alkaline phosphatase activity. Na+ uptake into the vesicles under equilibrium exchange conditions was significantly stimulated (P less than 0.01) nearly threefold in the presence of an outwardly directed H+ gradient as compared to no gradient. The stimulation by a H+ gradient was abolished in the presence of 0.5 mM amiloride. Measurements with the pH-sensitive dye BCECF in the absence of Na+ showed that 95.2 +/- 0.6 per cent of a 1.2 pH unit H+ gradient was dissipated from the vesicles in 2 min, but the remaining gradient was maintained for up to 15 min. These experiments therefore provide evidence that vesicles derived mainly from the maternal facing plasma membrane of syncytiotrophoblast layer II of the rat placenta possess a Na+/H+ exchanger.
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PMID:Preparation of plasma membrane vesicles from the rat placenta at term and measurement of Na+ uptake. 208 46

Alkaline phosphatase (ALP) activity has been demonstrated in periodontal ligament (PDL). On the basis of electron microscopic study, distribution of the enzyme in PDL tissue has also been indicated not only as a cell associated activity but also as an extracellular matrix associated activity. This study is concerned with the purification and characterization of the enzyme obtained from bovine PDL tissue. Purification of ALP extracted from the tissue included solubilization with 10 mM Tris-HCl buffer, pH 7.4, containing 0.2 mM MgCl2 and 0.1% Nonidet P-40 and fractionation by sequential chromatography utilizing DEAE-sephacel, Sepharose CL-6B and concanavalin A Sepharose 4B. Purity was established by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). This was followed by staining for ALP activity first with 2 mM beta-naphthyl acid phosphate and 1 mM Fast Blue BB Salt and then the protein with Coomassie Brilliant Blue. SDS-PAGE of the crude enzyme preparations gave a broad band with apparent molecular weight of 110,000-130,000 dalton. ALP activities were separated into two major peaks using Sepharose CL-6B chromatography. The void volume peak showed a purified form of 110,000 dalton ALP (110K ALP) while the second peak contained 120,000-130,000 dalton ALP (120-130K ALP) and other proteins. Sequentially, 120-130K ALP was purified by chromatography on concanavalin A Sepharose 4B. A polyclonal antibody was raised against purified bovine PDL 110K ALP in a rabbit. Immunodiffusion analysis showed that a polyclonal antibody against 110K ALP recognized 120-130K ALP. Analytical affinity chromatography on concanavalin A Sepharose 4B indicated that 110K ALP and 120-130K ALP had distinct affinity to the column which may depend upon the sugar chain structure. Digestion of 110K ALP with phosphatidylinositol-specific phospholipase C affected electrophoretic mobility but 120-130K ALP had no effect. It is suggested that 110K ALP is attached to a cell membrane anchored by a phosphatidylinositol glycan. In conclusion, bovine PDL contains two types of alkaline phosphatase i.e. 110K ALP and 120-130K ALP. Both ALPs are immunologically related although they have different sugar chain moieties. Furthermore, 110K ALP has a membrane anchoring domain. These results suggest that 110K ALP would be localized on the surface of the cell membrane and 120-130K ALP may associated with the extracellular matrix.
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PMID:[Purification and characterization of alkaline phosphatase obtained from bovine periodontal ligament]. 213 40

The aim of this work was to use preparations from germinating seeds of Pisum sativum to determine the apparent equilibrium constant of the reaction catalysed by sucrose-phosphate synthase (EC 2.4.1.14) and to compare this with the mass-action ratio of the reaction in the seeds. The apparent equilibrium constant ranged from 5.3 at 0.25 mM-MgCl2, pH 7.0, to 62 at 10 mM-MgCl2, pH 7.5. The sucrose phosphate content of the seeds, 23 nmol/g fresh wt., was determined by separating sucrose phosphate from sucrose by ion-exchange chromatography and then measuring the sucrose released by alkaline phosphatase. Comparison of equilibrium constants and mass-action ratios in the cotyledons of 38 h-germinated seeds showed that the reactions catalysed by glucose-6-phosphate isomerase, phosphoglucomutase and UDP-glucose pyrophosphorylase are close to equilibrium, and those catalysed by sucrose-phosphate synthase and sucrose phosphatase are considerably displaced from equilibrium in vivo.
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PMID:Apparent equilibrium constant and mass-action ratio for sucrose-phosphate synthase in seeds of Pisum sativum. 214 Feb 58

The characteristics of neutral cholesteryl ester hydrolase activities found in the microsomal and cytosolic subcellular fractions of rat lactating mammary tissue were investigated. The enzymes were assayed using cholesteryl oleate dispersed as a mixed micelle with phosphatidylcholine and sodium taurocholate (molar ratio 1:4:2) as substrate. This method gave activities approx. 20-fold higher than those seen when cholesteryl oleate was added in ethanol. Addition of phosphatidylcholine and sodium taurocholate to the assays using the ethanol-dissolved substrate did not increase the activities observed. When the cholesteryl oleate was dispersed with phosphatidylcholine only (molar ratio, 1:4) the activity of the two neutral cholesteryl ester hydrolases was also decreased considerably compared to that found with mixed micelles. In this case, however, approx. 60% of the cytosolic, but only 10% of the microsomal activity, was restored by separate addition of sodium taurocholate. The activities of both the microsomal and the cytosolic neutral cholesteryl ester hydrolases were inhibited by MgCl2, and this inhibition was almost completely reversed by the addition of an equimolar concentration of ATP. At a fixed concentration of MgCl2 increasing concentrations of ATP increased the enzyme activities in a dose-dependent way. The activity of the microsomal, but not the cytosolic enzyme was enhanced by a cyclic AMP-dependent protein kinase and both activities were inhibited by alkaline phosphatase (bovine milk). These results provide evidence for the regulation of neutral cholesteryl ester hydrolases in the rat lactating mammary gland by mechanisms involving phosphorylation-dephosphorylation and therefore suggest that these enzymes may be under hormonal control.
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PMID:Neutral cholesteryl ester hydrolase in the rat lactating mammary gland: regulation by phosphorylation-dephosphorylation. 217 66

The uptake of inorganic phosphate (Pi) was analyzed in monolayers and in apical membrane vesicles (AMV) of the established intestinal cell line CaCo-2. AMV, prepared by a MgCl2 precipitation technique, were enriched approximately 10-fold in alkaline phosphatase activity. Pi uptake into intact cells as well as into AMV was specifically dependent on the presence of sodium. In the presence of high sodium concentrations, the apparent Km for Pi was 214 +/- 17 mumol/l in monolayers and 300 +/- 19.7 mumol/l in AMV. Increasing the sodium concentration increased the apparent affinity of the transport system for Pi but hardly affected the maximal velocity (Vmax). At 0.1 mmol/l Pi and pH 7.4, the apparent Km for sodium was approximately 70 mmol/l in intact cells as well as in AMV. The results obtained in both systems suggested the involvement of two sodium ions and one phosphate ion in the transport process. Advancing confluence--independently of the age of the monolayers--reduced sodium-dependent uptake of Pi significantly by a decrease in Vmax, whereas the apparent Km for Pi remained unchanged. It is concluded that the apical membrane of CaCo-2 cells contains a sodium-dependent transport system for Pi.
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PMID:Sodium-dependent transport of Pi by an established intestinal epithelial cell line (CaCo-2). 242 Feb 7

The indoxyl-tetranitro BT method for the demonstration of alkaline phosphatase activity has been optimized and its validity for quantitative histochemistry tested. The study has been performed with model films of polyacrylamide gel incorporating homogenate of rat liver and with cryostat sections from the same livers. Addition of polyvinyl alcohol to the incubation medium greatly improved the localization of the final reaction product in cryostat sections. In polyacrylamide films, the formazan production specifically due to alkaline phosphatase was highest when using a medium containing 100 mM Tris-HCl buffer, pH 9.0, 0.2-1.0 mM substrate, 0.32 mM 1-methoxyphenazine methosulphate, 10 mM MgCl2, 5 mM sodium azide and 1 mM tetranitro BT. For the incubation of cryostat sections in the presence of polyvinyl alcohol, the same medium could be used but the optimum concentrations of substrate and tetranitro BT appeared to be 1-2 mM and 5 mM respectively. The test minus control reaction was specific for alkaline phosphatase activity and could be inhibited completely with tetramisole. The test minus control reaction was linear with time up to 30 min with model films and up to 15 min with cryostat sections. The formazan production was also linear with the amount of homogenate incorporated in model films and with section thickness up to 18 micron and therefore, the reaction obeyed the Beer-Lambert law. Variation of the substrate concentration yielded a KM of 0.05 mM for aqueous media and a KM of 0.55 mM for polyvinyl alcohol-containing media.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Quantification of the histochemical reaction for alkaline phosphatase activity using the indoxyl-tetranitro BT method. 243 56

Saito et al recently reported that the alkaline phosphatase (ALPase) of human periodontal ligament fibroblasts (HPLF) showed remarkably high activity which was similar, but not identical phenotype, to that present in osteoblasts, and suggested that HPLF could be termed as "osteoblastic fibroblast." The present study attempts to explore the ALPase synthesized on HPLF in relation to 1,25(OH)2D3. These HPLF were obtained by the explantation method and then subcultured in D-MEM containing 2 mg FCSP/ml, 50 micrograms ascorbic acid/ml and penicillin/streptomycin after trypsinization. The HPLF were inoculated at a cell density of 1.25 x 10(4) cells/cm2 in culture wells. After 24hr, the HPLF were treated every two days for 7 days with 0.5-10nM 1,25 (OH)2D3. Then, ALPase activity, DNA and protein contents were assayed by the methods using p-nitrophenylphosphate, diaminobenzoic acid and Coomassie Brilliant Blue, respectively. Also, ALPase was prepared from the confluent HPLF incubated with 5 nM 1,25 (OH)2D3 for 12 days, and digested with and without trypsin. The crude ALPase which was solubilized with 10mM Tris-HCl, pH 7.4 containing 0.2 mM MgCl2 and 0.1% NP-40 was applied to 5-15% gradient SDS-PAGE and stained with beta-naphththylacid phosphate and First Blue BB salt in 60 mM borate buffer pH 9.7. The cell growth which was assayed by DNA contents and the incorporation of 3H-thymidine was decreased by 1,25(OH)2D3. On the other hand, ALPase activity was increased approximately 3.6 fold at 6 day by the addition of 5 nM 1,25(OH)2D3. From the separation of ALPase activity on SDS-PAGE, 110 K and 120-130 K ALPase were identified. The 110 K ALPase, which was not changed by 1,25(OH)2D3, was converted to 100K, releasing 10K peptide after trypsin treatment. This 110K ALPase might be tightly associated with cell membrane structure. The 120-130K ALPase was remarkably increased by 1,25(OH)2D3 on SDS-PAGE and completely digested with trypsin. The ALPase in the cultured HPLF might be located not only on the plasma membrane but also in the extracellular matrix. Therefore, 1,25(OH)2D3 may regulate the cell cycle and also the gene expression of ALPase of HPLF.
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PMID:[Biochemical study of human periodontal ligament fibroblasts--1,25 (OH)2D3 dependent alkaline phosphatase]. 248 52

Alkaline phosphatase from mouse intestinal epithelial cells catalyzes the synthesis of pyrophosphate from Pi during hydrolysis of either glucose 6-phosphate, ATP, ADP, inorganic pyrophosphate or p-nitrophenylphosphate. The rate of pyrophosphate synthesis is increased by MgCl2 and by decreasing the pH of the medium from 8.5 to 6.0. The data presented indicate that at the catalytic site of alkaline phosphatase the energies of hydrolysis of the phosphoserine residue and of pyrophosphate are different from those measured in aqueous solutions.
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PMID:Energy transduction at the catalytic site of enzymes: hydrolysis of phosphoester bonds and synthesis of pyrophosphate by alkaline phosphatase. 255 25

A procedure for the selective fractionation of the bone and liver alkaline phosphatase activity in tissue extracts and human sera is proposed. Optimized conditions of the assay are: urea 3.7 mol/l in 0.5 mol/l DEA buffer, pH 9.8; 0.5 mmol/l MgCl2; 10.0 mmol/l p-nitrophenyl phosphate. The sample is diluted 1:20 in the reagent solution and the activity is recorded for 10 min at 37 degrees C. By means of a computerized or manual graphic analysis, based on 'peeling-off' the exponentials, the two differently urea-sensitive subforms are identified and the slow-(liver) and the fast-decaying (bone) activities are easily discriminated and their respective values calculated. Interference due to the intestinal isoenzyme can be also accounted for. The analytical variability is very satisfactory (within run CV = 7.5 and 4.5% for osseous and hepatic form, respectively; day-to-day CV less than 10% for both). The lower limits of detection are about 10 U/l and the serum or plasma reference values together with the influence on the assay of hemoglobin and protein content are also investigated.
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PMID:Time-resolved fractionation of bone and liver alkaline phosphatase activities with a 'peeling-off' method. 270 14

The properties of the enzymes involved in Ca2+-stimulated breakdown of phosphatidylinositol 4'-phosphate (PIP), phosphatidylinositol 4',5'-bisphosphate (PIP2), and phosphatidic acid (PA) in rabbit erythrocyte ghosts were studied. At 25 degrees C, 1 to 180 microM Ca2+ rapidly stimulated the breakdown of PIP and PIP2, and maximal breakdown occurred within 10 minutes at all Ca2+ concentrations. The rate and the total amount of breakdown of PA, PIP, and PIP2 increased with Ca2+ concentration. MgCl2 inhibited the rate of Ca2+-stimulated breakdown of PIP and PIP2 at Ca2+ concentrations less than 10 microM, but did not have any appreciable effects at higher Ca2+ concentrations. MgCl2 also protected against Ca2+-stimulated breakdown of PA. In the presence and absence of 5 mM MgCl2, Ca2+ stimulated half-maximal breakdown of PIP and PIP2 at 2-3 microM under hypotonic and isotonic conditions. In the presence of 5 mM MgCl2, Ca2+-stimulated breakdown of PIP and PIP2 was associated with the release of Pi and inositol bisphosphate. In the absence of MgCl2, Ca2+ stimulated the release of 32P-labeled Pi, inositol bisphosphate, and inositol trisphosphate from labeled PIP, PIP2, and PA. Ca2+ increased phosphatidylinositol content and decreased PIP and PIP2 content in these membranes. The results of this investigation suggest that Ca2+ stimulates the breakdown of polyphosphoinositides by stimulating polyphosphoinositide phosphomonoesterase and phosphodiesterase activities in rabbit erythrocyte ghosts. These activities were activated by less than 3 microM Ca2+ in the presence of MgCl2 under hypotonic or isotonic conditions. These Ca2+-stimulated polyphosphoinositide phosphoesterase activities could therefore be active under physiological conditions in normal rabbit erythrocytes.
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PMID:Ca2+-stimulated phospholipid phosphoesterase activities in rabbit erythrocyte membranes. 298 4


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