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)

The effect of Fusarium sporotrichiella v. sporotrichioides mycotoxin (sporofusarin) on the total and non-sedimentary supernatant activity of 13 marker-enzymes of subcellular particles (2 mitochondrial enzymes-cytochrome oxidase and malate dehydrogenase; 8 lysosomal enzymes -- acid phosphatase, acid RNAase, acid DNAase, arylsulphatases A and B, beta-N-acetylglucosaminidase, beta-glucuronidase, beta-galactosidase and beta-glucosidase; 2 microsomal enzymes -- glucose-6-phosphatase and acetylesterase; plasma membrane enzyme -- alkaline phosphatase) of the rat liver, kidney, spleen and bone-marrow was studied in in vivo experiments. The latter demonstrated that sporofusarin effects were characterized by a significant organ and organella specificity, viz. the toxin caused a sharply increased activity, mainly of lysosomes enzymes and labilization of the lysosomal membranes, primarily in the spleen and the bone-marrow. A conclusion is drawn that the discovered selective destructive action of sporofusarin on the lysosomes may be regarded as a new phenomenon that, possibly is directly related to the characterization of the mechanism responsible for a specific effect produced by sporofusarin.
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PMID:[Lysosomal component in the mechanism of the toxic effect of sporofusarin]. 94 27

Effects of antitumor agents on rat liver microsomal drug-metabolizing enzyme activities and thymus lymphocytes were studied in male Wistar rats. High doses of 5-fluorouracil (5-FU) and cyclophosphamide (CP) given parenterally for 6 days caused a partial decrease in whole body weight and the microsomal enzyme content such as cytochrome P-450 and cytochrome b5. Aniline p-hydroxylase and aminopyrine N-demethylase activities also decreased in rats dosed for 5 days decreased compared with the control. Both compounds in the high concentrations produced spectral change of "modified type II". However, the magnitude of the spectral changes observed was independent of the the concentration of substrate added. The addition of NADPH to the microsomes-substrate mixture modified the spectral change. Both drugs caused a considerable decrease in thymus weight and the number of thymus lymphocytes, while the alkaline phosphatase activity was enhanced in 5-FU groups, indicating that the agents cause a significant involution of the thymus. Decrease in the total number of the lymphocytes was greater than that in the blood leucocytes.
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PMID:Antitumor agents. I. Effect of 5-fluorouracil and cyclophosphamide on liver microsomes and thymus of rat. 100 1

The 5'-phosphomonoesterase activity of 5'-nucleotidase (EC 3.1.3.5) and alkaline phosphatase (EC 3.1.3.5) participates in the catabolism of purine ribonucleotides to uric acid in humans. Initial velocity studies of 5'-nucleotidase suggest a sequential mechanism of interaction between AMP nad MgCl2, with a Km of 14 and 3 muM, respectively. With product inhibition studies the apparent Ki's for adenosine, inosine, cytidine, and inorganic phosphate were 0.4, 3.0, 5.0, and 42 mM, respectively. A large number of nucleoside mono-, di-, and tri-phosphate compounds were inhibitors of the enzyme. Allopurinol ribonucleotide, ADP, or ATP were competitive inhititors when AMP was the substrate, with a Ki slope of 120 muM. The phosphomonoesterase activity of human placental microsomal alkaline phosphatase had a pH optimum of 10.0 and had only 18% of maximum activity at pH 7.4. Substrates and inhibitors included almost any phosphorylated compound. The Km for AMP was 0.4 mM and the apparent Ki for Pi was 0.6 mM. Activity was increased only 19% by 5 mM MgCl2. These observations suggest that 5'-nucleotidase and alkaline phosphatase may be inhibited by ATP and Pi, respectively, under normal intracellular conditions, and that AMP may be preferentially hydrolyzed by 5'-nucleotidase.
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PMID:Purine catabolism in man: inhibition of 5'-phosphomonesterase activities from placental microsomes. 101 16

Changes in protein elution patterns and among others in the distribution profiles of some isozymes, as the lysosomal acid phosphatase, the microsomal alkaline phosphatase, the cytoplasmic fraction of aspartate aminotransferase and some fractions of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, have been found in liver experimental fatty change induced in rats by carbon tetrachloride and ethionine. The possible meaning of these changes is discussed.
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PMID:Rat liver isozymes in acute carbon tetrachloride and ethionine poisoning. 112 37

The binding of [125I]endothelin-1 (125I-ET-1) to membranes from whole rat brain, from individual brain regions, and derived from subcellular fractionation of whole rat brain was investigated. 125I-ET-1 binding to whole rat brain membranes was rapid, concentration-dependent, saturable, and characterized as irreversible because it was not displaced by unlabeled endothelin-1 (ET-1) and different concentrations of ligand produced, with time, a similar magnitude of binding. The maximum binding site capacity and second-order forward rate association constant of binding were 1,946 +/- 147 fm/mg protein and 5.53 +/- 1.72 x 10(6) M-1 s-1. Removal of either extramembranal calcium or membrane-bound calcium and calcium binding proteins did not affect the binding of 125I-ET-1 to whole rat brain membranes. The brain stem and cerebellum contained the highest levels of 125I-ET-1 binding sites, whereas the cerebral cortex, striatum, and hippocampus contained binding site levels three- to fourfold less. Subcellular fractionation of whole rat brain and subsequent analyses of the distribution of 125I-ET-1 binding demonstrated a twofold enrichment of binding sites in the synaptosomal fraction compared to the homogenate. The myelin fraction contained a similar density of binding sites compared to the homogenate, while the mitochondrial and microsomal fractions contained considerably less binding sites. The ribosomal fraction did not contain any 125I-ET-1 binding sites. The subcellular distribution of 125I-ET-1 binding sites did not correlate with the distribution of 5'-nucleotidase, cytochrome-C oxidase, phosphodiesterase, and alkaline phosphatase. Depletion of extracellular calcium increased 125I-ET-1 binding in the synaptosomal fraction but not in the myelin and mitochondrial fractions.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regional and subcellular distribution of [125I]endothelin binding sites in rat brain. 131 99

1. Alkaline phosphatase is covalently bound to bovine mammary microsomal membranes and milk fat globule membranes through linkage to phosphatidylinositol as demonstrated by the release of alkaline phosphatase following treatment with phosphatidylinositol-specific phospholipase C. 2. The release of alkaline phosphatase from the pellet to the supernatant was demonstrated by enzyme assays and electrophoresis. 3. Electrophoresis of the solubilized enzymes showed that the alkaline phosphatase of the microsomal membranes contained several isozymes, while only one band with alkaline phosphatase activity was seen in the fat globule membrane. 4. Levamisole and homoarginine were potent inhibitors of the alkaline phosphatase activities in both membrane preparations and in bovine liver alkaline phosphatase, but not in calf intestinal alkaline phosphatase.
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PMID:Alkaline phosphatase in the lactating bovine mammary gland and the milk fat globule membrane. Release by phosphatidylinositol-specific phospholipase C. 137 15

Cystic fibrosis is caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR), which lead to defective Cl- conductance in epithelial cells. While the CFTR gene product has been detected in the plasma membrane, its presence and functional role in the membranes of intracellular compartments remain to be established. The purpose of the present experiments was to functionally localize CFTR in the endosomal membrane and to test the role of the associated Cl- conductance in the regulation of endosomal pH (pH(en)). When using conductive protonophores, the net H+ flux across the endosomal membrane of Chinese hamster ovary (CHO) cells is limited by the movement of counterions. Thus, ionic permeability could be estimated indirectly, from the changes in pH(en) determined fluorimetrically. Measurements in situ and in a cell-free microsomal preparation indicate the presence of a protein kinase A (PKA)-activated anion conductance in endosomes from CHO cells transfected with CFTR, but not in endosomes from wild-type or mock-transfected cells. In endosomes isolated from CFTR-expressing cells, the stimulatory effect of PKA was diminished by a specific peptide inhibitor of PKA, by alkaline phosphatase treatment or by a monoclonal antibody against the second nucleotide binding fold of CFTR. Increasing counterion permeability by phosphorylation of CFTR or by addition of valinomycin failed to alter the rate or extent of endosomal acidification in situ. Our observations indicate that functional CFTR, susceptible to activation by PKA, is present in endosomes of transfected CHO cells. More importantly, the data suggest that factors other than counterion permeability are the major determinants of pH(en).
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PMID:The cystic fibrosis transmembrane regulator is present and functional in endosomes. Role as a determinant of endosomal pH. 137 35

Placental alkaline phosphatase (PLAP) belongs to a class of proteins that are anchored to the plasma membrane by a COOH-terminal phosphatidylinositol-glycan (PI-G) moiety. Nascent forms of such proteins undergo NH2- and COOH-terminal processing to yield the mature PI-G-tailed proteins. We previously introduced a shortened engineered form of preproPLAP (preprominiPLAP) that permits monitoring in cell-free preparations its sequential processing to the pro form and then to the mature PI-G-tailed form. Previous studies were carried out by synthesizing the preproprotein cotranslationally in the presence of rough microsomal membranes (RM). Because of the complexity of the cotranslational system it was not possible to determine whether cofactors were required for processing. We have now prepared RM that are preloaded with prominiPLAP but contain little mature PI-G-tailed miniPLAP. Maximal processing requires supplementation with both ATP and GTP. Inhibitors of PI-G biosynthesis do not affect processing. Since cleavage and PI-G addition are presumably catalyzed by a transamidase, the nucleoside triphosphate requirements suggest that there are additional steps in prominiPLAP processing prior to transamidation with PI-G. These may involve translocation of the pro protein in a proper conformational state to the transamidase site.
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PMID:Phosphatidylinositol-glycan (PI-G)-anchored membrane proteins: requirement of ATP and GTP for translation-independent COOH-terminal processing. 138 69

Hepatic microsomal activities of acyl-CoA:cholesterol acyltransferase (ACAT) and 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase, rate-limiting enzymes in cholesterol esterification and cholesterol synthesis, and the concentration sand compartmentalization of esterified and unesterified cholesterol, were studied in carp acclimated to 10 and 30 degrees C. Irrespective of acclimation temperature, carp-liver ACAT is characterized by an apparent Km-value for oleoyl-CoA of 11-15 microM and displays an optimum activity at pH 7.4. The enzyme activity is reduced approx. 2-fold upon preincubation of microsomes with alkaline phosphatase. Arrhenius plots of ACAT-activity are curvilinear, with curvatures considerably affected by the acclimation temperature of the fish. Carp HMG-CoA reductase has been characterized previously by Teichert and Wodtke ((1987) Biochim. Biophys. Acta 920, 161-170). When measured at 30 degrees C, ACAT activities from 30 degrees C- and 10 degrees C-acclimated carp are identical (approx. 6 pmol/min per mg protein), whilst 'expressed' HMG-CoA reductase activity (18.1 +/- 12.2 pmol/min per mg protein for 30 degrees C-acclimated carp vs. 159.8 +/- 106.6 pmol/min per mg protein for 10 degrees C-acclimated carp) is enhanced 9-fold in the cold environment. This disparity indicates that cold-acclimation results in a massive increase in the capacity for hepatic cholesterol synthesis relative to hepatic cholesterol esterification. At the same time, hepatic compositional analysis reveals identical contents of unesterified cholesterol in either groups of carp but significantly decreased (3-fold) amounts in cholesterol ester (and also in triacylglycerol, 4-fold) in cold-acclimated carp. Moreover, microsomal fractions display lower cholesterol to phospholipid ratios in the cold. In contrast, concentrations of either cholesterol fractions (and of triacylglycerols) in plasma--the mobile compartment for lipoprotein transport--do not differ in cold- and warm-acclimated carp. Based on current concepts of cholesterol metabolism, it is concluded that the cold-enhanced expression of hepatic HMG-CoA reductase activity is a homeostatic response directed against and compensating for a cold-induced but not yet characterized deficiency in hepatic cholesterol availability.
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PMID:Acyl-CoA: cholesterol acyltransferase and 3-hydroxy-3-methylglutaryl-CoA reductase in carp-liver microsomes: effect of cold acclimation on enzyme activities and on hepatic and plasma lipid composition. 145 Feb 16

Placental alkaline phosphatase (PLAP) has been used as a model for studying the biosynthesis of the phosphatidylinositol-glycan (PI-G)-protein linkage in intact cells and in cell-free systems. However, for the study of processing in cell-free systems, a small protein devoid of glycosylation sites is preferable. A PLAP-derived cDNA was engineered that codes for a nascent protein (mini-PLAP) of 28 kDa in which the NH2- and COOH-termini are retained but most of the interior of PLAP is deleted. In vitro translation of mini-PLAP mRNA in the presence of rough microsomal membranes yields mature PI-G-tailed mini-PLAP. Processing of nascent mutant proteins occurs only when a small amino acid is located at the site of cleavage and PI-G attachment (omega site). Mutations adjacent and COOH-terminal to the omega site have revealed that the omega + 1 site is promiscuous in its requirements but that only glycine and alanine are effective at the omega + 2 site. Rough microsomal membranes from T cells deficient in PI-G biosynthesis do not support processing of mini-PLAP; addition of exogenous PI-G restores activity. Translocation of the proprotein, most likely requiring ATP and GTP, precedes COOH-terminal processing.
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PMID:Placental alkaline phosphatase: a model for studying COOH-terminal processing of phosphatidylinositol-glycan-anchored membrane proteins. 145 93


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