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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 acid phosphate activity (APA) associated with the isolated brush border membrane of the tapeworm, Hymenolepis diminuta, hydrolyzed p-nitrophenyl phosphate (PNPP), pyrophosphate (PPi), and beta-glycerophosphate (beta GP). Inhibition of PNPP hydrolysis at pH 4.0 was inhibited in a competitive manner by the following compounds (listed in order of decreasing affinity with their apparent inhibitor constants (Ki')): molybdate (0.031 mM); PPi (0.147 mM); NaF (0.150 mM); o-carboxyphenyl phosphate (0.261 mM); inorganic phosphate (0.770)); arsenate (3.45 mM); tartrate (22.1 mM); and beta GP (29.8 mM). Cu2+, formaldehyde, and arsenite at 10:1, 80:1, and 200:1 inhibitor to substrate ratios did not inhibit APA. The maximal rate of hydrolysis (Vmax) of each substrate was greater at pH 4.0 than 5.0. The apparent Michaelis constant (Km') for PNPP increased from 0.233 to 0.351 mM when the pH was raised from 4.0 to 5.0. The Km' for PPi decreased from 0.101 to 0.046 mM, while the Km' for beta GP changed from 2.04 to 2.22 mM under similar circumstances. APA and alkaline phosphatase activity increased as a function of temperature up to 45 degrees C.
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PMID:Hymenolepis diminuta: further characterization of the membrane-bound acid phosphatase activity associated with the brush border membrane of the tapeworm's tegument. 185 Nov 2

Several compounds were tested as inhibitors of the alkaline phosphatase (AlkPase) activity associated with the isolated brush border membrane of the tapeworm, Hymenolepis diminuta. Molybdate, arsenate, arsenite and beta-glycerophosphate (BGP) were competitive inhibitors of the hydrolysis of p-nitrophenyl phosphate, while levamisole and clorsulon were uncompetitive and mixed inhibitors, respectively. Molybdate was also a competitive inhibitor of the hydrolysis of BGP and 5'-adenosine monophosphate, and levamisole was an uncompetitive inhibitor of BGP hydrolysis. The apparent inhibitor constants (Ki') for molybdate and levamisole were virtually identical regardless of the substrate, and these data support the hypothesis that the AlkPase activity is represented by a single membrane-bound enzyme with low substrate specificity. Quinacrine, Hg2+, and ethylenediaminetetraacetate were also potent inhibitors of the AlkPase activity, but the mechanisms by which these latter three inhibitors function were not clear.
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PMID:Competitive, uncompetitive, and mixed inhibitors of the alkaline phosphatase activity associated with the isolated brush border membrane of the tapeworm Hymenolepis diminuta. 276 48

The effects of the phenothiazine, Stelazine, on Hymenolepis diminuta were investigated. The cestode was incubated for 10 min at 37 degrees C with 1 mM trifluoperazine, in the presence and absence of Ca2+. Assay of brush border enzymes showed that drug treatment lowered the activities of alkaline phosphatase, Ca2+-ATP'ase, 5'-nucleotidase and type 1 phosphodiesterase. This occurred in parallel with a significant reduction in tegumental protein. Under these conditions gross changes in ultrastructural appearance and cellular organization were observed. There was a lack of ordered microtriches and the distal cytoplasm was absent. Glycogen granules were scattered throughout the cytoplasm within the subtegumental layer. The connective tissue also appeared to be in some disarray. The effects of Stelazine appeared to be dependent on time and were significantly increased when Ca2+ was included in the incubation medium. Incubation with the less hydrophobic phenothiazine trifluoperazine sulphoxide had minimal effect on the integrity of the cestode. The results reported here support the premise that certain phenothiazines may be considered as potential cestocidal agents.
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PMID:Biochemical and ultrastructural investigation of the effect of Stelazine (trifluoperazine) on Hymenolepis diminuta (Cestoda). 302 50

Proteins of the isolated brush border membrane of Hymenolepis diminuta were hydrolyzed in vitro by chymotrypsin, papain, pepsin, subtilopeptidase A (= subtilisin Carlsberg), and trypsin. Neither proteolytic nor amidase activity was demonstrable in the isolated membrane using proteinaceous (casein and hemoglobin) or chromogenic (benzoyl-arginine-p-nitroanilide and succinyl-alanyl-alanyl-propyl-phenylalanine p-nitroanilide) substrates, and the membrane preparation did not inhibit the proteolytic and amidase activities of these enzymes. Thus, the isolated tegumental membrane of H. diminuta is not inherently resistant to the action of proteolytic enzymes, and it does not inhibit proteolytic activity. In control incubations containing only buffer, the alkaline phosphatase activity of the brush border membrane decreased in a time dependent manner, but in the presence of chymotrypsin, subtilopeptidase A, and trypsin, the membrane retained greater alkaline phosphatase activity (pepsin and papain could not be tested for this effect on alkaline phosphatase activity). A similar time dependent decrease in activity was also noted for each of the proteolytic enzymes in control assays, but subtilopeptidase A and papain retained greater activity in the presence of the isolated membrane preparation when these assays were compared to controls.
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PMID:Hymenolepis diminuta: interactions of the isolated brush border membrane with proteolytic enzymes. 330 86

The isolated brush border membrane of the tapeworm, Hymenolepis diminuta, hydrolyzes p-nitrophenyl phosphate over a broad pH range. Acid phosphatase activity (pH optimum at 4.0) is inhibited specifically by sodium dodecyl sulfate (SDS) and NaF, while the alkaline phosphatase activity (pH optimum at 8.8) is inhibited specifically by levamisole, 2-mercaptoethanol, and ethylenediaminetetra-acetate (EDTA). These two phosphatase activities are further differentiated in that (1) there is a rapid decrease in alkaline phosphatase activity when the membrane preparation is incubated at pH 4.0, while there is little loss of acid phosphatase activity, and (2) the alkaline phosphatase activity is solubilized with no loss of activity when the membrane is treated with Triton X-100, while such treatment causes a significant loss of acid phosphatase activity. Both activities are nonspecific and hydrolyze a variety of phosphorylated compounds, but the relative activities of the two phosphatases against these substrates vary significantly.
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PMID:Acid phosphatase activity in the isolated brush border membrane of the tapeworm, Hymenolepis diminuta: partial characterization and differentiation from the alkaline phosphatase activity. 341 89

The brush border membrane of Hymenolepis diminuta contains several Ca2+-dependent enzymes. Following our isolation of a Ca2+-dependent modulator protein we examined the kinetic properties of the brush border marker alkaline phosphatase from fractionated and crude tegument. We show that this enzyme is inhibited by Ca2+ concentrations approaching those in the calcareous corpuscles of H. diminuta.
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PMID:Ca2+ inhibition of brush border alkaline phosphatase activity in Hymenolepis diminuta. 393 97

Pyrophosphate, p-nitrophenyl phosphate and a variety of pyrimidine and purine nucleotides are hydrolyzed by the solubilized membrane-bound enzymes of the brush border plasma membrane of Hymenolepis diminuta. The pH optima (or ranges) for hydrolysis of substrates are 8.0 (pyrophosphate), 8.8 (p-nitrophenyl phosphate), 8.4-8.9 (nucleoside monophosphates), and 7.1-8.1 (nucleoside triphosphates); all substrates, with the exception of nucleoside triphosphates, have a higher affinity for the solubilized enzyme at pH 7.4 than at their optimal pH for hydrolysis. ATP is degraded completely by the enzyme preparation to adenosine and inorganic phosphate, but since neither ADP nor ATP accumulate in the incubation medium it is not known whether ATP hydrolysis involves the sequential hydrolysis of terminal phosphate groups. Isoelectric focusing and various chromatographic procedures (gel permeation, ion-exchange and hydrophobic interaction chromatography) fail to separate the alkaline phosphatase, phosphodiesterase, 5'-nucleotidase, adenosine triphosphatase and ribonuclease activities associated with the solubilized membrane preparation. Additionally, inhibitor studies indicate that only a single enzyme with low substrate specificity is involved in the hydrolysis of nucleotides, p-nitrophenyl phosphate, pyrophosphate and hexose phosphate esters. Purines and pyrimidines and their nucleosides interact with the active site, and in some instances activity of the enzyme is stimulated by an unknown mechanism.
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PMID:Nucleotide hydrolysis by solubilized membrane-bound enzymes of the brush border plasma membrane of Hymenolepis diminuta. 613 88

The isolated, brush-border membrane of Hymenolepis diminuta contained an enzyme which hydrolyzed phosphodiester bonds. This enzyme appeared to be a Type I phosphodiesterase (E. C. 3.1.4.1) (produces nucleoside 5'-phosphates) and had no activity against synthetic, Type II phosphodiesterase substrates (mononucleotides substituted at the 3' position). The effects of various potential inhibitors of enzymatic activity, and cation requirements of this enzyme, demonstrated a distinct difference between the phosphodiesterase and alkaline phosphatase activities of the isolated, brush-border membrane. SDS-polyacrylamide gel electrophoresis of the isolated membrane preparation, followed by localization of phosphodiesterase activity in the gels, indicated the enzyme had a molecular weight of approximately 87,000. Thus, the phosphodiesterase activity represents a previously undescribed, membrane-bound enzyme of the brush-border of Hymenolepis diminuta.
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PMID:Type I phosphodiesterase in the isolated, brush-border membrane of Hymenolepis diminuta. 627 42

Preparations of isolated brush border plasma membrane of Hymenolepis diminuta and H. microstoma possess the following enzymatic activities: alkaline phosphohydrolase (E.C. 3.1.3.1); Type I phosphodiesterase (E.E. 3.1.4.1); ribonuclease (E.C. 3.1.4.22); adenosine triphosphatase (E.C. 3.6.1.3); and 5'-nucleotidase (E.C. 3.1.3.5). The following enzymatic activities could not be demonstrated in either membrane preparation: Type II phosphodiesterase (E.C. 3.1.4.18); cyclic adenosine-3', 5'-monophosphate phosphodiesterase (E.C. 3.1.4.17); leucine aminopeptidase (E.C. 3.4.11.1); maltase (alpha-glucosidase; E.C. 3.2.1.20); and lactase (beta-galactosidase; E.C. 3.2.1.23). These data generally agree with those of previous studies in which similar membrane-bound enzymes were demonstrated in intact (living) worms.
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PMID:A comparison of membrane-bound enzymes of the isolated brush border plasma membranes of the cestodes of Hymenolepis diminuta and H. microstoma. 628 Jan 22

The ability of nonionic detergents to solubilize the membrane-bound enzymes of the brush-border plasma membrane of Hymenolepis diminuta was investigated. Of the detergents tested (Triton X-100, Tween 80, Brij 35, Lubrol PX and WX, W-1, and beta-octyl-D-glucoside), only Triton was an effective solubilizing agent. Optimal solubilization was achieved by incubating an isolated fraction of the brush-border membrane in the presence of 1% Triton X-100 for 60 min at 37 C, followed by centrifugation at 100,000 g for 60 min at 25 C. This treatment resulted in solubilization of 94% of the alkaline phosphohydrolase, 91% of the phosphodiesterase and ribonuclease, and 88% of the 5'-nucleotidase activities. The pH optima for enzymes solubilized in nonionic and ionic detergents (Triton and sodium dodecyl sulfate, respectively) did not differ. Isoelectric focusing of the Triton-solubilized material demonstrated the presence of at least 14 polypeptides, a majority of which had isoelectric points below pH 7.
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PMID:Solubilization of the membrane-bound enzymes of the brush-border plasma membrane of Hymenolepis diminuta (Cestoda) using nonionic detergents. 628 6


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