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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 ATPase of matrix vesicles is not stimulated by calcium ions, nor do the vesicles have any capacity to metabolize glucose. ADPase of high activity is also present; thus vesicles cannot be a component of the conventional ATP cycle, in which energy is stored by phosphorylating ADP and released by hydrolyzing the resultant ATP. These results do not support speculations that matrix vesicles might function by concentrating calcium via an energy-dependent ion transport system such as those found in the plasma membrane and the sarcoplasmic reticulum. Matrix vesicles' alkaline phosphatase can be solubilized by treatment with certain detergents: sodium dodecyl sulfate (12 mM and 16 mM), cetylpyridinium chloride (14mM), and deoxycholic acid (DOC, 14 MM). The first two detergents denature the enzyme during storage whereas DOC does not. DOC will also solubilize ATPase and inorganic pyrophosphatase. Yields of the three enzymes are 85-95%. Dialysis of a DOC digest of vesicles removes DOC and 43% of protein, and also causes much of the alkaline phosphatase to become particulate once again.
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PMID:Matrix vesicles of bovine fetal cartilage: metabolic potential and solubilization with detergents. 12 41

The purpose of this study was to try to differentiate histochemically between the various enzymes which may catalyze the hydrolysis of ATP in developing rat dental tissues. Freeze cut and freeze dried sections of molar and incisor teeth were incubated in lead capture-based media at pH 5.0, 7.2 or 9.4 with one of the following substrates: beta-glycerophosphate, AMP, ADP, ATP, AMP-PNP and tetrasodium pyrophosphate. To establish the enzymatic nature of the hydrolysis parallel sections were incubated after prior fixation in either formaldehyde or glutaraldehyde. By comparing the enzymatic stainings obtained with the various substrates and at the different pH:s, it was concluded that ATP can be visibly hydrolyzed in rat dental tissues by alkaline phosphatase (stratum intermedium, apical part of maturation ameloblasts, basal part of all ameloblasts, odontoblasts and subodontoblastic layer), specific ATPase (apical and basal parts of secretory ameloblasts) and ATP pyrophosphatase and/or adenylate cyclase (stratum intermedium, odontoblasts). Acid phosphatase, specific ADPase, 5'-nucleotidase, inorganic pyrophosphatase, 3':5'-cyclic-AMP-phosphodiesterase and adenylate kinase on the other hand, seem not to be engaged in the ATP hydrolysis to such a degree as to complicate the interpretation of the histochemical staining. The alkaline phosphatase part of the ATP hydrolysis appeared to be rather insensitive to aldehyde fixation, while the hydrolysis effected by specific ATPase and ATP pyrophosphatase and/or adenylate cyclase was extinguished after fixation with formaldehyde for 4 h or glutaraldehyde for 10 min.
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PMID:Adenosine triphosphate hydrolysis in rat dental tissues. A histochemical study to differentiate the enzymes involved. 18 60

The intracellular location of a variety of enzymes was studied in Amoeba proteus with the use of electron microscopic cytochemical methods, in an attempt to assess the relationships between different membranous organelles. One group of enzymes, including nucleoside diphosphatases (IDPase, UDPase, GDPase, ADPase), carbamoyl phosphatase, alkaline phosphatase, and BAXD oxidase was localized mainly in the rough endoplasmic reticulum, nuclear envelope, and convex side of the Golgi apparatus. Esterase activity had a similar localization except that the Golgi apparatus was "stained" throughout most of its extent. A second group of enzymes was found in Golgi cisternae and vesicles, and in come vacuoles. This group included acid phosphatase, thiamine pyrophosphatase, and aryl sulfatase. Some enzymes previously detected in cytoplasmic membranes of other cells, including glucose-6-phosphatase, showed little or no activity in amoebae. The results suggest that there are chemical similarities and probable functional relationships between the rough endoplasmic reticulum, the nuclear envelope, and the convex side of the Golgi apparatus. On the other hand, the concave pole of the Golgi apparatus, aggregates of smooth tubules and vesicles, and the cell surface appear more closely related to one another than to the endoplasmic reticulum and the convex side of the Golgi apparatus. The cytochemical similarity between the Golgi apparatus and certain vacuoles such as food vacuoles may reflect the role of the Golgi apparatus in the formation of lysosomes. The locations of reaction products of the various enzymes in amoebae are compared with observations reported for other cell types.
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PMID:Relationships between membranous organelles in amoebae studied by electron microscopic cytochemical staining. 19 99

It was found that mitochondria from human placenta exhibited an ADPase activity with the following characteristics. The enzyme responsible for this activity was associated with the inner mitochondrial membrane. It was not released by treatment of the submitochondrial particles with solutions of high ionic strength. Maximal ADP hydrolysis was reached at pH 8. Specific inhibitors for alkaline phosphatase (L-phenylalanine), myokinase (P1,P5-di(adenosine-5')pentaphosphate), or 5'-nucleotidase (concanavalin A) did not decrease ADP hydrolysis. ATP synthesis from ADP by myokinase was about 13 nmol/mg/min, whereas ADP hydrolysis reached values around 500 to 550 nmol/mg/min, indicating that a myokinase-H+ATPase combination could not account for the observed rates of ADP hydrolysis. The activity was stimulated by Mg2+, but high concentrations of this cation produced inhibition. High ADP concentrations did not inhibit ADPase activity. Kinetic measurements of the activity in the submitochondrial particles showed that the true substrate was ADP-Mg. The kinetic studies showed V(app) values of 476 and 270 nmol/mg/min, and Kmapp values of 416 and 8.7 microM.
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PMID:Subcellular localization and properties of adenosine diphosphatase in human placenta. 147 Jun 6

Mature secretory granules in paraneurons contain ATP amongst other small messenger molecules. In the islet organ such stores of adenine nucleotides readily can be demonstrated by means of the quinacrine fluorescence method. ATP is co-released together with other granule constituents when the major hormones are exocytosed. The distribution of ATP splitting enzymic activities was studied in the pancreas of the mouse and rat, in order to obtain information on the possible fate of this small messenger molecule. ATPase, ADPase, and AMPase (5'-nucleotidase) were demonstrated with lead precipitation methods, L-tetramisole was used to inhibit unspecific alkaline phosphatase (alPase); alPase activities were shown with tetrazolium methods, using 5-bromo-4-chloro-3-indoxyl phosphate as substrate. Most endothelial cells of the vascular bed, both in the exocrine and in the endocrine pancreas, are reactive for ATPase, ADPase, AMPase and alPase. Smooth muscle cells are strongly reactive for ATPase and AMPase, vascular adventitial fibroblasts (veil cells) stain for ATPase and alPase, as do some lamellar cells at the islets surface. Staining for ADPase serves as a selective method to demonstrate the vascular bed. Comparable results are obtained with the alPase reaction, though insular non-B-cells are also reactive. ATPase staining is less useful for demonstrating vascular connections because moderate reactivity of exocrine parenchyma and adventitial tissue obscures the picture. AMPase activity is strong in the venous segments of the capillary net and in collecting veins but the reaction obviously does not demonstrate significant portions of the residual capillary network. Weak AMPase activity is seen in the insular parenchyma.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Fate of ATP in secretory granules: phosphohydrolase studies in pancreatic vascular bed. 255 47

Using electron microscope cytochemistry and cells separated on Ficoll-Hypaque, Mg2+-dependent ATPase, ADPase and 5'-nucleotidase were predominantly localized as ectoenzymes on normal human granulocytes. Large deposits of ATPase final reaction product and more finely granular deposits of 5'-nucleotidase final reaction product were firmly attached to the outer surface of cell plasma membranes. The final reaction product from ecto-ADPase was, however, only loosely associated with the plasma membrane. In addition, finer deposits of ADPase final reaction product were seen in specific granules and in background cytoplasm. No nucleotidase phosphatase activity was localized to the alkaline phosphatase-containing granules (phosphasomes) recently described by Rustin et al. In granulocytes from patients with chronic granulocytic leukaemia, ecto-ATPase had a patchy distribution on the plasma membranes. There was considerable heterogeneity between cells with regard to ADPase and 5'-nucleotidase localization. In some cells, ADPase was seen only at both site, while in some cells no activity was detected. 5'-Nucleotidase localization was normal in some cells but lacking from many. No correlation was found between enzyme heterogeneity and the degree of morphological cell maturity.
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PMID:Electron microscopic cytochemical localization of nucleoside phosphatases in normal and chronic granulocytic leukaemic human neutrophils. 611 13

Apyrase (ATP-diphosphohydrolase, EC 3.6.1.5) and inorganic pyrophosphatase (EC 3.6.1.1) were partially purified from S. aureofaciens RIA 57 and characterized. Apyrase degrades, in addition to ATP, other nucleoside triphosphates and nucleoside diphosphates, diphosphate, thiamine diphosphate, phosphoenolpyruvate and oligophosphates of chain length n less than 90. The apyrase activity was detected in the membrane and supernatant fractions. Its properties (substrate specificity. effect of inhibitors, pH optimum and effect of Mg2+ ions) were similar in both fractions except for the effect of oligomycin that inhibited only the membrane fraction. Pyrophosphatase exhibited a strict substrate specificity, substrates other than diphosphate being degraded relatively slowly. Of other enzymes exhibiting the phosphatase activity acid phosphatase (EC 3.1.3.2) and alkaline phosphatase (EC 3.1.3.1), trimetaphosphatase (EC 3.6.1.2) and exopolyphosphatase (EC 3.6.1.11) degrading oligophosphatase of chain length n = 15, 40 and 60, were detected.
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PMID:Properties of apyrase and inorganic pyrophosphatase in Streptomyces aureofaciens. 612 57

Adenosine diphosphatase (ADPase) activities were studied in human polymorphonuclear leukocytes with a recently developed radio-assay. The neutrophils were homogenized in isotonic sucrose and subjected to analytical subcellular fractionation. The sucrose density gradient fractions were assayed for ADPase activity and for principal organelle marker enzymes. ADPase activity was distributed between the plasma membrane, specific granule and soluble fractions. The plasma membrane and specific granule activities had similar kinetic and inhibitor properties but the cytosolic enzyme was clearly different. Studies with the non-penetrating inhibitor diazotized sulphanilic acid and measurements of latent activity indicate that plasma membrane ADPase activity is located on the external aspect to the cell. Its possible role in inhibiting platelet aggregation is discussed. Neutrophils were isolated from control subjects, patients with chronic granulocytic leukaemia and patients in the third trimester of pregnancy. The specific activities (mU/mg protein) of ADPase activity, in contrast to those of alkaline phosphatase, were similar in all three groups. This result, together with fractionation experiments and inhibition studies strongly suggests that ADPase activity is not attributable to neutrophil alkaline phosphatase.
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PMID:Subcellular localization and properties of adenosine diphosphatase activity in human polymorphonuclear leukocytes. 626 31

Enzyme cytochemical and immunocytochemical techniques at the light and electron microscope levels were used to study the distribution of potential markers of chemical transformation in rodent bladders. In rat tumours induced by in vivo treatment with methylnitrosourea, alkaline phosphatase localization was normal on the external surface of the plasma membranes of some cells but abnormal in others where reaction product was seen only on intracellular membranes. 5'-Nucleotidase localization was abnormal in all cells, being seen on endoplasmic reticulum and nuclear membranes only, while in normal bladders only ectoenzyme localization was seen. Heterogeneity of alkaline phosphatase amd 5'-nucleotidase localization was seen on the plasma membranes of these tumours after 15 days in organ culture. Some cells produced enzyme and others did not; in other cells only parts of the membrane reacted heavily, while other regions were negative. In transformed cell cultures and tumours of mouse bladder derived by in vitro treatment of explants with dimethylbenz (a) anthracene, a bimodal pattern of alkaline phosphatase localization was seen. Cells had either normal ectoenzyme reaction product or abnormal intracellular membrane reaction product. 5'-Nucleotidase and ADPase were lost after transformation while cAMP-phosphodiesterase was retained as an ectoenzyme. Mg.ATPase and a cAMP-independent, calcium-insensitive 'protein phosphatase' were induced in transformed cell cultures. An epithelial antigen was detected in the cytoplasm of both normal and transformed cells associated with reticular cytoplasmic ground substance, plasma membrane vesicles and cytoskeletal elements.
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PMID:Cytochemical markers of bladder carcinogenesis. 627 42

Human placental chorioepithelial brush border membrane, which is in direct contact with maternal blood flow, has platelet aggregation inhibiting activity. In the present study, the mechanism of this action has been examined in relation to ADP (adenosine diphosphate) degrading activity and alkaline phosphatase activity of brush border membrane vesicles (BBMV). BBMV prepared from human early and term placental villi, inhibited platelet aggregation induced by ADP. BBMV had potent ADP degrading (ADPase) activity. ADP was quickly degraded by BBMV. ADP degrading activity of BBMV was not so different between early and term placenta. Alkaline phosphatase activity of late placental BBMV was about three times greater than that of early placental BBMV. On the other hand, ADP degrading activity of late placental BBMV was almost the same as that of early placental BBMV. Inhibiting activity of platelet aggregation induced by ADP and ADP degrading activity of BBMV, were not inhibited by levamisole (alkaline phosphatase inhibitor).
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PMID:Platelet aggregation inhibiting activity of human placental chorioepithelial brush border membrane vesicles--the role of alkaline phosphatase. 806 52


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