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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 enzyme inorganic pyrophosphatase (PPiase, EC 3.6.1.1) from the odontoblastic layer of rat incisors has been studied by means of a radiochemical micromethod. The enzyme was incubated with 32P-pyrophosphate in tris-HCl buffer at 37 degrees C. The reaction was linear with time for at least 45 min, and the pH optimum was found to be 8.8, independent of the amount of pyrophosphate present. Heating the enzyme at 56 degrees C inhibited the enzyme activity rapidly, Mg2+ ions activated the enzyme by 15% at an ion concentration of 4 mM, while higher concentrations were inhibitory. Ca2+ ions and PO43-ions inhibited the enzyme at all concentrations. F- ions did not affect the PPiase at concentrations below 8 mM, whereas higher concentrations had an inhibiting effect. Urea was found to inhibit the enzyme at concentrations above 1.5 M, while EDTA was a strong inhibitor at very low concentrations. The characteristics of PPiase agree well with the properties of the enzyme nonspecific alkaline phosphatase (EC 3.1.3.1.) studied earlier.
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PMID:Determination of inorganic pyrophosphatase in rat odontoblast layer by a radiochemical method. 0 Jul 84

A purine nucleoside triphosphate phosphohydrolase (unspecified diphosphate phosphohydrolase, EC 3.6.1.15) was chromatographically separated from the bulk of alkaline phosphatase activity by gel filtration chromatography of butanol and EDTA extracts of fracture callus and bovine epiphyseal cartilage. The callus enzyme differed from alkaline phosphatase in a variety of characteristics. The purine nucleoside triphosphate phosphatase hydrolyzed a more specific group of substrates, required Ca2+ and Mg2+ for optimal activity, remained unaffected by a potent alkaline phosphatase inhibitor, and demonstrated a narrower range of optimal pH for catalytic activity. The enzyme was localized in the microsomal pellet following subcellular fractionation of callus chondrocytes. These characteristics indicate a role for the enzyme in Ca2+ transport.
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PMID:Identification, characterization and localization of a (Ca2+ + Mg2+)-activated purine nucleoside triphosphate phosphohydrolase from calcifying cartilage. 3 14

Purified chondrocytic alkaline phosphatase (orthophosphoric-monoester phosphohydrolase (alkaline optimum), EC 3.1.3.1) from bovine fetal epiphyseal cartilage hydrolyzes a variety of phosphate esters as well as ATP and inorganic pyrophosphate. Optimal activities for p-nitrophenyl phosphate, ATP and inorganic pyrophosphate are found at pH 10.5, 10.0 and 8.5, respectively. The latter two substrates exhibit substrate inhibition at high concentrations. p-Nitrophenyl phosphate demonstrates decreasing pH optima with decreasng substrate concentration. Heat inactivation studies indicate that both phosphorolytic and pyrophosphorolytic cleavage occur at the same site on the enzyme. Mg2+ (0.1-10.0 mM) and Mn2+ (0.01-0.1 mM) show a small stimulation of p-nitrophenyl phosphate-splitting activity at pH 10.5. Levamisole, Pi, CN-, Zn2+ and L-phenylalanine are all reversible inhibitors of the phosphomonoesterase activity. Pi is a competitive inhibitor with a Ki of 10.0 mM. Levamisole and Zn2+ are potent non-competitive inhibitors with inhibition constants of 0.05 and 0.04 mM, respectively. The chondrocytic alkaline phosphatase is inhibited irreversibly by Be2+, EDTA, EGTA, ethane-1-hydroxydiphosphonate, dichloromethane diphosphonate, L-cysteine, phenyl-methylsulfonyl fluoride, N-ethylmaleimide and iodoacetamide. NaCL, KCL and Na2SO4 at 0.5-1.0 M inhibit the enzyme. At pH 8.5, the cleavage of inorganic pyrophosphate (pyrophosphate phosphohydrolase, EC 3.6.1.1) by the chondrocytic enzyme is slightly enhanced by low levels of Mg2+ and depressed by concentrations higher than 1mM. Ca2+ show only inhibition. Similar effects of Mg2+ and Ca2+ on the associated ATPase (ATP phosphohydrolase, EC 3.1.6.3) activity were observed. Arrhenius studies using p-nitrophenyl phosphate and AMP as substrates have accounted for the ten-fold difference in V in terms of small differences in both the enthalpies and entropies of activation which are 700 cal/mol and 2.3 cal/degree per mol, respectively.
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PMID:Enzymatic characterization of the chondrocytic alkaline phosphatase isolated from bovine fetal epiphyseal cartilage. 4 Jun 3

A survey of the hydrolytic activity of alkaline phosphatase (EC 3.1.3.1) reveals that PP1, like phosphomonoesters, can serve as substrate in vitro. This pp1-phosphohydrolytic activity can be distinguished from PP1-phosphohydrolytic activities of inorganic pyrophosphatases (EC 3.6.1.1) and glucose-6-phosphatase (EC 3.1.3.9) by several criteria. Discrimination among these hydrolytic enzymes is possible by their dependence on variation of pH and of magnesium to PP1 ratios in the assay solutions. The true substrates and modifiers are not simply PP1 and magnesium, but the equilibrium species in mixtures of these two. The physiological significance of each of the three enzymes is not predictable from their differential efficiency as catalysts of PP1-hydrolysis in vitro.
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PMID:Enzyme catalyzed hydrolysis of inorganic pyrophosphate. Current view of problems in characterization of PP1-phosphohydrolytic activity associated with alkaline phosphatases (EC 3.1.3.1). 23 7

Fractions composed primarily of cells (Fraction I), membrane fragments (Fraction II) and matrix vesicles (Fraction III) were isolated from chick epiphyseal cartilage. The characteristics of the alkaline phosphatase (EC 3.1.3.1), pyrophosphatase (EC 3.6.1.1) and ATPase (EC 3.6.1.3) activities in the matrix vesicle fraction were studied in detail. Mg-2-+ was not absolutely essential to any of the activities, but at low levels was stimulatory in all cases. Higher concentrations inhibited both pyrophosphatase and ATPase activities. Both the stimulatory and inhibitory effects were pH-dependent. Ca-2-+ stimulated all activities weakly in the absence of Mg-2-+. However, when Mg-2-+ was present, Ca-2-+ was slightly inhibitory. Thus, none of the activities appear to have a requirement for Ca-2-+, and hence would not seem to be involved with active Ca-2-+ transport in the typical manner. The distribution of alkaline phosphatase, pyrophosphatase, and Mg-2-+ ATPase activities among the various cartilage fractions was identical, and concentrated primarily in the matrix vesicles. Conversely, the highest level of (Na-+ + K-+)-ATPase activity was found in the cell fraction. All activites showed nearly identical sensitivities to levamisole (4 - 10-3 M) which caused nearly complete inhibition of alkaline phosphatase and pyrophosphatase. About 10-15% of the ATPase activity was levamisole-insensitive. The data are consistent with the concept that the Mg-2-+-ATPase and pyrophosphatase activities of matrix vesicles stem from one enzyme, namely, alkaline phosphatase.
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PMID:Studies on matrix vesicles isolated from chick epiphyseal cartilage. Association of pyrophosphatase and ATPase activities with alkaline phosphatase. 23 58

The properties of a highly purified inorganic pyrophosphatase (pyrophosphate phosphohydrolase; EC 3.6.1.1) from pig scapula cartilage were studied. The enzyme had a molecular weight of 66 000 and a pH optimum of 7-8. It was markedly activated by magnesium, but not, or only to a much smaller degree, by other metal ions. PP1 was the only substrate found and had a Km value of 11 muM. The enzyme was not inhibited by phosphate and other inhibitors of alkaline phosphatase such as CN- minus, amino acids and theophylline; it was slightly inhibited by tartrate, formaldehyde and ammonium molybdate and strongly inhibited by F- minus, Ca2+ and other metal ions. The properties of the enzyme in the presence of concentrations of PP1 present in plasma (3.5 muM) were similar to those found at higher (2 mM) concentrations of PP1. The diphosphonates ethane-1-hydroxy-1,1-diphosphonate and dichloromethylenediphosphonate inhibited the enzyme in the presence of low PP1 concentrations. The characteristics of this enzyme are therefore similar to pyrophosphatases from other sources, such as from yeast and erythrocytes, and do not support a specific role of this enzyme in the calcification process.
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PMID:Properties of inorganic pyrophosphatase of pig scapula cartilage. 23 96

1. The adoption of a meal-eating pattern of feeding by rats altered the alkaline phosphatase (EC 3.1.3.1) activity in serum and liver. It was therefore necessary to regulate the feeding pattern of both magnesium-deficient rats and control animals receiving a Mg-adequate diet in order to study the effect of the deficiency. 2. Mg deficiency decreased the activities of alkaline phosphatase and inorganic pyrophosphatase (EC 3.6.1.1) in serum, kidney and tibia, but increased them in spleen. 3. Addition of a standard concentration of exogenous Mg to tissue extracts usually increased the activity of corresponding enzymes from Mg-deficient and control rats by the same proportion, indicating that the main effect of the deficiency was on the amount of enzyme present rather than on the efficiency of its operation. 4. Certain quantitative differences in the response to exogenous Mg and the activity ratio, alkaline phosphatase:inorganic pyrophosphatase were found between tissues from Mg-deficient and control rats. The significance of these are discussed in relation to the association of the two enzymic activities with the same protein molecule, and the possible occurrence of isoenzymes.
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PMID:Changes in the alkaline phosphatase (EC 3.1.3.1) and inorganic pyrophosphatase (EC 3.6.1.1) activities of rat tissues during magnesium deficiency. The importance of controlling feeding pattern. 100 75

The characteristics of nonspecific alkaline phosphatase, (APase, EC 3.1.3.1.) measured as beta-glycerophosphatase (GPase, EC 3.1.3.1.), inorganic pyrophosphatase (PPiase, EC 3.6.1.1.) and adenosine triphosphatase (ATPase, EC 3.6.1.3.) were studied in detail of butanol extracts prepared from rat molar cementum. Mg2+ was not absolutely essential to any of the activities, but at low levels was stimulatory in all cases. Higher concentrations were inhibitory. Ca2+ stimulated ATPase activity weakly at low levels, but was slightly inhibitory to the other enzyme activities. All enzyme activities showed nearly identical sensitivities to heat inactivation and to L-p-bromotetramisole and levamisole, which caused nearly complete inhibition. About 10-15% of the ATPase activity was insensitive to L-p-bromotetramisole and levamisole. The data are consistent with the concept that GPase, PPiase and ATPase activities of cementum to a major part stem from one enzyme, namely nonspecific alkaline phosphatase.
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PMID:Properties of alkaline phosphatases from cellular cementum of rat molars. 612 76

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

The effects of fluoride on the activities of acid phosphatase (EC 3.1.3.2) from potato and alkaline phosphatase (EC 3.1.3.1) from E. coli during pyrophosphate and p-nitrophenylphosphate hydrolysis and on the activities of inorganic pyrophosphatase (EC 3.6.1.1) from baker's yeast during pyrophosphate hydrolysis were compared. For both phosphatases the type of interaction was found to be independent on the nature of substrate. For acid phosphatase and inorganic pyrophosphatase the inhibition was of non-competitive and uncompetitive types, respectively. In the case of alkaline phosphatase fluoride increased the rate of p-nitrophenol release during p-nitrophenylphosphate hydrolysis at pH greater than or equal to 7.9 without affecting the rate of phosphate release, which is indicative of fluorophosphate formation in the course of the transphosphorylation reaction. The data obtained suggest the existence of essential differences in the mechanisms of fluoride effects on the three enzymes under study.
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PMID:[Comparative effects of fluoride on three enzymes, hydrolyzing pyrophosphate - acid and alkaline phosphatases and inorganic pyrophosphatase]. 612 20


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