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)

Brush-border microvillous plasma membrane vesicles were prepared from human full-term placental syncytiotrophoblasts and purified 33-fold from the homogenate with reference to a membrane marker enzyme, alkaline phosphatase (EC 3.1.3.1). Transport of alpha-(methylamino)isobutyrate by the membrane vesicles was stimulated in the presence of an Na+ gradient from the outside to the inside of the vesicles. The initial rate of uptake in a 10-s period was enhanced with increasing concentration of Na+ in the external medium. The level of alpha-(methylamino)isobutyrate transported into the vesicles reached a maximum 1 min after the start of incubation at 37 degrees C, and then decreased with time due to efflux. Extrapolation to infinite medium osmolarity showed no uptake, indicating transport of alpha-(methylamino)isobutyrate into membrane vesicles. The initial rate of uptake was dependent on temperature and pH: the highest rate occurred at 37 degrees C and the optimal pH was 8.0. When the alpha-(methylamino)isobutyrate concentration was varied, the initial rate of uptake dependent on an Na+ gradient (out greater than in) obeyed Michaelis-Menten kinetics with Km and Vmax values of 1.07 mM and 3.23 nmol/10 s per mg of protein, respectively. Cross-inhibition patterns indicated that at least three Na+-dependent and two Na+-independent carrier-mediated pathways existed in the human placental brush border. One Na+-dependent pathway interacted with all substrates tested. Another Na+-dependent route interacted with L-proline, alpha-(methylamino)isobutyrate, and L-methionine, while a third pathway was selective for L-methionine. One Na+-independent pathway was selective for L-cysteine, while the other pathway interacted with all substrates tested.
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PMID:Characterization of amino acid transport systems in human placental brush-border membrane vesicles. 366 75

Interaction of purified human liver and placental alkaline phosphatases (orthophosphoric-monoester phosphohydrolase (alkaline optimum), EC 3.1.3.1) with sulfhydryl groups, sulfhydryl reagents, and Mg2+ were studied. L-Cysteine (0.1 mmol/l) or Mg2+ activated the liver enzyme 4-5-fold and the placental enzyme 2-3-fold, with optimal pH 7.5-8.0; these activations were not additive. L-Cysteine (2 mmol/l) inhibited both enzymes maximally at pH greater than 9.0; phosphate protected the enzymes. S-Methylcysteine had little effect, with or without Mg2+. Inhibition by sulfur-containing compounds paralleled their ability to bind Zn2+. Fluoresceine mercury acetate (specific for sulfhydryl groups) inhibited the isoenzymes, whereas iodoacetic acid, iodoacetamide, dithionitrobenzoic acid, and p-chloromercuribenzoate had little effect. The inhibition was reversed by L-cysteine and only slightly protected by inorganic phosphate. Thus, there are two sites on human liver and placental alkaline phosphatase that interact with L-cysteine; a Mg2+-binding site, which results in activation, and a site that involves one or both of the bound Zn2+ ions and results in inactivation. Both enzymes have a protected essential thiol group.
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PMID:Modulation of activity of human alkaline phosphatases by Mg2+ and thiol compounds. 394 54

The lipid composition and fluidity of brush-border membranes prepared from rat proximal and distal colonocytes were determined. Fluidity, as assessed by steady-state fluorescence polarization techniques using the fluorophores 1,6-diphenyl-1,3,5-hexatriene, DL-2(9-anthroyl)stearic acid and DL-12(9-anthroyl)stearic acid, was decreased in distal compared to proximal plasma membranes. This pattern was similar to that previously described for both antipodal plasma membranes in rat enterocytes of the small intestine. The decrease in fluidity of the distal as compared to the proximal membranes resulted from an increase in cholesterol content, cholesterol/phospholipid molar ratio and degree of saturation of the fatty acid residues in the distal membranes. The specific activities of total alkaline phosphatase and cysteine-sensitive alkaline phosphatase, enzymes previously shown to be functionally dependent on the physical state of the colonic brush-border membrane's lipid, were also significantly lower in distal as compared to proximal clonic plasma membranes. These studies, therefore, demonstrate that differences in the lipid fluidity, lipid composition and certain enzymatic activities exist in brush-border membranes prepared from rat proximal and distal colonocytes. The regional variation in rat colonic luminal membrane lipid fluidity and composition may, at least partially, be responsible for differences in these enzymatic activities as well as in sodium and water absorption along the length of this organ.
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PMID:Regional differences in the lipid composition and fluidity of rat colonic brush-border membranes. 404 47

We demonstrated that alkaline phosphatase was localized on the cell membrane of Dictyostelium discoideum amebae and on isolated plasma membranes. The enzyme activity was specifically inhibited by 0.01 M KCN or cysteine. The same method could also be applied to baker's yeast and MDCK cells (dog kidney cells in vitro).
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PMID:Cytochemical localization of alkaline phosphatase in the cell membrane of Dictyostelium discoideum amebae. 404 10

Alkaline phosphatase prepared from mammalian cell cultures was found to have alkaline inorganic pyrophosphatase activity. Both of these activities appear to be associated with a single protein, as demonstrated by: (1) concomitant purification of alkaline phosphatase and alkaline inorganic pyrophosphatase; (2) proportional precipitation of alkaline phosphatase and inorganic pyrophosphatase activities by titrating constant amounts of an enzyme preparation with increasing concentration of antibody; (3) immune electrophoresis, which showed that precipitin bands that have alkaline phosphatase activity also have pyrophosphatase activity; (4) inhibition of pyrophosphatase activity by cysteine, an inhibitor of alkaline phosphatase activity; (5) similar subcellular localization of the two enzyme activities as demonstrated by histochemical methods; (6) hormonal and substrate induction of alkaline phosphatase activity in mammalian cell cultures, which produced a nearly parallel rise in inorganic pyrophosphatase activity.
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PMID:Alkaline inorganic pyrophosphatase activity of mammalian-cell alkaline phosphatase. 496 63

The mechanisms by which phosphate regulates the activity of alkaline phosphatase (orthophosphoric monoester phosphohydrolase, EC 3.1.3.1) in rat kidney were investigated. Measurements of incorporation of [(14)C]leucine into kidney alkaline phosphatase in rats fed on complete or phosphate-free diet provide evidence of a twofold increase in the rate of synthesis of the enzyme in diet-treated animals. Cycloheximide experiments indicated that control and diet-adapted enzyme decreases in activity according to first-order kinetics with a calculated half-life of 10.3 and 6.5h after complete and phosphate-free diet administration respectively. Basal and diet-adapted enzymes exhibit similar K(m) values for several phosphomonoesters and an identical degree of inhibition is produced by cysteine. In addition, the enzyme from both sources is the same with regard to heat inactivation at 45, 56 or 64 degrees C, to the profile of elution from Sephadex and to electrophoretic properties on polyacrylamide gel. A failure of rat kidney alkaline phosphatase to respond to cortisol (hydrocortisone) was also observed.
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PMID:Molecular aspects of the regulation of rat kidney alkaline phosphatase. 511 52

D-myo-Inositol 1,4,5-trisphosphate has been previously demonstrated to act as a second messenger for the hormonal mobilization of intracellular calcium in rat liver. In this study, the breakdown of D-myo-inositol 1,4,5-trisphosphate by a phosphatase activity was characterized. Using partially purified subcellular fractions, it was found that D-myo-inositol 1,4,5-trisphosphate phosphatase (I-P3ase) specific activity was highest in the plasma membrane fraction, while D-myo-inositol 1,4-bisphosphate phosphatase specific activity was highest in the cytosolic and microsomal fractions. The plasma membrane I-P3ase was Mg2+-dependent with optimal activity observed at 0.5-1.5 mM free Mg2+. The enzyme had a neutral pH optimum, suggesting that it was neither an acid nor alkaline phosphatase. Neither LiCl nor NaF inhibited the I-P3ase activity. However, both L-cysteine and dithiothreitol stimulated the activity 2-fold. Spermine (2.0 mM) inhibited the I-P3ase activity by 50%, while putrescine and spermidine had little or no effect.
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PMID:Characterization of D-myo-inositol 1,4,5-trisphosphate phosphatase in rat liver plasma membranes. 609 66

Kupffer cells are the sinusoidal macrophages of the liver. Using ultrastructural phosphatase cytochemical methods, we examined the relationship between the Golgi apparatus, GERL, and lysosomes of Kupffer cells in fetal rat livers identified, in part, by their ability to phagocytize intravenously injected latex spheres. Thiamine pyrophosphatase (TPPase) activity was localized to the inner Golgi saccules and some vesicles in the Golgi region but not to GERL. A TPPase-like activity, demonstrable in lysosomes, was abolished by sodium fluoride but not suppressed by the alkaline phosphatase inhibitors L-cysteine and L-p-bromotetramisole. Acid phosphatase (AcPase) was localized by GERL, some coated vesicles, and in lysosomes, but not to the Golgi stacks. Continuities between GERL and lysosomes were observed. Phagosomes containing internalized latex spheres received TPPase and AcPase sequentially. TPPase was localized in phagosomes immediately after latex administration. AcPase activity was not found here until at least 10 minutes following the injection of the particulates. Our findings indicate that Kupffer cell lysosomes are derived from GERL, but also suggest that phagosomes may receive material packaged by the Golgi apparatus as well as GERL.
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PMID:The relationships between the Golgi apparatus, GERL, and lysosomes of fetal rat liver Kupffer cells examined by ultrastructural phosphatase cytochemistry. 611 32

Phosphohydrolase activity of a highly enriched commercial preparation of calf intestinal alkaline phosphatase was stimulated in the presence of HCO3. SO4, Cl, SCN, and acetate did not stimulate hydrolysis, whereas SO3 exhibited a bimodal effect, stimulating at low (25mM) concentration but inhibiting at high (100 mM) concentration. The pH optimum of this stimulation by HCO3 or SO3 was 8.5--9.0 and was maximal at a Mg concentration of 0.5 mM. HCO3 increased the Vmax of the reaction without changing the Km for ATP. ATP, GTP, UTP, and xanthosine triphosphate were equally effective as substrates, whereas AMP and p-nitrophenyl phosphate were much less effective. Alkaline phosphatase activity was inhibited by L-cysteine and L-phenylalanine, compounds that also inhibited the HCO3-ATPase activity of the preparation. Passage of the commercial preparation through an anion-exchange column yielded a fraction with enriched alkaline phosphatase and HCO3-ATPase activities; this fraction proved to be a single protein on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, on isoelectric focusing, and by immunologic techniques. These studies strongly suggest that alkaline phosphatase and anion-stimulated phosphohydrolase activities are properties of the same protein in small intestine. It is possible that alkaline phosphatase may function as a HCO3-ATPase involved in intestinal absorption and secretion.
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PMID:Anion-stimulated phosphohydrolase activity of intestinal alkaline phosphatase. 615 12

Oral administration of 2-mercapto-2-methylpropanoyl-L-cysteine (SA 96), a newly synthesized sulfhydryl compound, showed protective and curative effects on adjuvant-induced arthritis in rats similarly to those seen with D-penicillamine (D-PA). However, the effects of these compounds were not dose-dependent, and the maximum effects of SA96 were observed at 10 mg/kg/day. On the contrary, SA96 and D-PA had little effect on the various acute and subacute inflammatory responses induced in rat and mice. Formation of hemolytic plaque forming cells in the spleen of mice immunized with 5 X 10(8) sheep red blood cells was potentiated by the oral administration of both compounds. These stimulatory effects of SA96 and D-PA on the humoral immune responses were also not dose-dependent, and the maximum effects of SA96 were observed with 10 mg/kg/day, as in the case of adjuvant-induced arthritis in rats. In in vitro experiments, the inactivation of rheumatoid factor and the inhibition of collagenase and bone alkaline phosphatase activities were observed with both compounds, but these effects of SA96 were more potent than those of D-PA. As there is a similarity in the pharmacological profiles of SA96 and D-PA, SA96 may prove to be clinically effective for rheumatoid arthritis.
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PMID:[Pharmacological studies of new sulfhydryl compounds 2-mercapto-2-methylpropanoyl-L-cysteine (SA96). I. Evaluation of anti-rheumatic action (author's transl)]. 624 2


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