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 presence of Ca2+-ATPase activities with high-affinity sites for Ca2+ in brush border as well as basolateral plasma membranes of rat duodenal epithelium has been reported previously (Ghijsen, W.E.J.M. and van Os, C.H. (1979) Nature 279, 802-803). Since both plasma membranes contain alkaline phosphatase (EC 3.1.3.1), which also can be stimulated by Ca2+, the substrate specificity of Ca2+-induced ATP-hydrolysis has been studied to determine whether or not alkaline phosphatase and Ca2+-ATPase are two distinct enzymes. In basolateral fragments, the rate of Ca2+-dependent ATP-hydrolysis was greater than that of ADP, AMP and p-nitrophenylphosphate at Ca2+ concentrations below 25 muM. At 0.2 mM Ca2+ the rates of ATP, ADO, AMO and p-nitrophenylphosphate hydrolysis were not significantly different. In brush border fragments the rates of ATP, ADP and AMP hydrolysis were identical at low Ca2+, but at 0.2 mM Ca2+, Ca2+-induced hydrolysis of ADO and AMO was greater than either ATP or p-nitrophenylphosphate. Alkaline phsophatase in brush border and basolateral membranes was inhibited by 75% after addition of 2.5 mM theophylline. Ca2+-stimulated ATP hydrolysis at 1 muM Ca2+ was not sensitive to theophylline in basolateral fragments while the same activity in brush border fragments was totally inhibited. At 0.2 mM Ca2+, Ca2+-induced ATP hydrolysis in both basolateral and brush border membranes was sensitive to theophylline. Oligomycin and azide had no effect on Ca2+-stimulated ATP hydrolysis, either at low or at high Ca2+ concentrations. Chlorpromazine fully inhibited Ca2+-stimulated ATP hydrolysis in basolateral fragments at 5 muM Ca2+, while it had no effect in brush border fragments. From these results we conclude that, (i) Ca2+-ATPase and alkaline phosphatase are two distinct enzymes, (ii) high-affinity Ca2+-ATPase is exclusively located in basolateral plasma membranes, (iii) alkaline phosphatase activity, present on both sides of duodenal epithelium is stimulated slightly by low Ca2+ concentrations, but this Ca2+-induced activity is inhibited by theophylline and shows no specificity with respect to ATP, ADP or AMP.
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PMID:Dissociation between Ca2+-ATPase and alkaline phosphatase activities in plasma membranes of rat duodenum. 644 11

Alkaline phosphatase from Streptomyces hygroscopicus strain JA 5999-R 27-158 was purified and characterized. The enzyme was found in the culture filtrate and in the mycelium. The phosphatase was extracted from the mycelium and purified by adsorption to DEAE-cellulose. To separate impurities, the crude enzyme solution was heated and the phosphatase purified by chromatography through CM-Sepharose and Sephadex G 100. The specific activity of the resulting enzyme was 1000 microMol/min/mg at 25 degrees C. The molecular weight determined by SDS gel electrophoresis was found to be 56 000. The Michaelis-Menten constant determined with p-nitrophenylphosphate as substrate was Km = 1.25 X 10(-3) M. Phosphatase activity was dependent on the presence of Ca++ and the maximum activity of enzyme with p-nitrophenylphosphate as substrate was found at pH 9.2. The pI as detected by isoelectric focusing was at pH 5.6. Temperatures from 30 degrees to 75 degrees C did not affect the stability of the enzyme. The alkaline phosphatase exhibited high substrate specificity; of various phosphomonoesters tested, only p-nitrophenylphosphate, methylumbelliferyl-phosphate, phosphoenolpyruvate, ADP, ATP and tyrosine-O-phosphate was hydrolysed. The activity was inhibited by NAF, Na2P2O7 and EDTA. The involvement of the alkaline phosphatase in the regulation of secondary metabolism was discussed.
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PMID:[Metabolism of phosphate-limited Streptomyces cultures. I. Purification and characterization of alkaline phosphatase produced by Streptomyces hygroscopicus]. 653 19

A (2'-5')An synthetase activity was isolated from human placental extracts by affinity chromatography on poly(rI) . poly(rC)-agarose. The oligonucleotide (2'-5')An was identified by (1) chromatography on PEI-cellulose and DEAE-cellulose, (2) inhibition of polypeptide synthesis in lysed rabbit reticulocytes (3) competition of the binding of pppA(pA)3,3'-[32P]pCp to rabbit reticulocyte lysates, and (4) alkaline phosphatase digestion. The synthetase activity in most placental preparations is activated by natural or synthetic dsRNA. However, in a few placental synthetase preparations, dsRNA is only marginally stimulatory and only becomes effective by prior treatment of the enzyme preparations with the calcium-dependent micrococcal nuclease. This suggests that there is an endogenous placental dsRNA contaminant in the enzyme preparations. In some synthetase preparations, a second dsRNA-stimulated product, tentatively identified as the nucleotide 5'-IMP, is also observed. Because the specific AMP deaminase inhibitor coformycin (10 microM) blocks the formation of IMP from ATP and causes a quantitative accumulation of AMP, and because the formation of IMp becomes independent of dsRNA when ADP or AMP is used in place of ATP, the presence of a dsRNA-stimulated ATP phosphohydrolase (ATPase) activity in human placenta is suggested.
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PMID:Double-stranded RNA-stimulated enzyme activities isolated from human placental extracts. 662 76

ADP-ribosyl protein lyase, formerly termed ADP-ribosyl histone-splitting enzyme (Okayama, H., Honda, M., and Hayaishi, O. (1978) Proc. Natl. Acad. Sci. U. S. A. 75, 2254-2257), was purified approximately 4,000-fold from rat liver and characterized. The purified enzyme exhibited a single protein band at the position of Mr = 83,000 upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme split the bond between ADP-ribose and histone H2B or H1, and also acted on ADP-ribosyl pentapeptide (Pro-(ADP-ribosyl)Glu-Pro-Ala-Lys) of H2B but not its deadenylylated derivative, phosphoribosyl pentapeptide. The enzyme cleaved the bond between histone and mono(ADP-ribose), but hardly cleaved the bond with oligo- or poly(ADP-ribose). The enzymatic product was close to, but not identical with, ADP-ribose. The terminal ribose residue, obtained by hydrolysis of the split product by snake venom phosphodiesterase and alkaline phosphatase, was identified as 3-deoxy-D-glycero-pentos-2-ulose by the following gas chromatography-mass spectrometric analyses: 1) the reduced sugar was a mixture of 3-deoxy-threo- and 3-deoxy-erythro-pentitol, and 2) the deuterated reduced sugar was identical with that derived from synthetic 3-deoxy-D-glycero-pentos-2-ulose. This result indicated that the direct product was 5'-ADP-3"-deoxypent-2"-enofuranose, a dehydrated form of ADP-ribose, and that the enzyme is a lyase and not a hydrolase.
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PMID:ADP-ribosyl protein lyase. Purification, properties, and identification of the product. 669 7

The observation that NAD inhibits sodium-dependent phosphate (P) uptake by the luminal brush border membrane (BBM) of the proximal tubule prompted us to examine the specificity and mechanism of this process. Addition of 10(-5) M NAD to the perfusate of isolated perfused rabbit proximal straight tubules inhibited lumen-to-bath P flux by approximately 50%. ADP-ribose had an identical effect, whereas nicotinamide had no effect. ADP and 5'-AMP (10(-5) M) also inhibited P flux. Na-dependent uptake of 32P by rabbit BBM vesicles was inhibited by 0.1-0.3 mM NAD, ADP-ribose, ADP, ATP, 5'-AMP, and GDP, which were preincubated with the vesicles for 30 min. The kinetics of inhibition showed an apparent increase in the Km for P but no change in Vmax. These findings are consistent with "competitive inhibition." The nucleotides inhibited P uptake even when BBM alkaline phosphatase was inhibited by 96% with 10 mM theophylline. Evidence of nonspecific phosphatase activity was present, since incubation of BBM with 0.1 mM solution of nucleotides for 30 min resulted in an elevation of free P in the medium of approximately 0.15-0.22 mM. Correction of 32P specific activity for this change resulted in values for Km and Vmax that were not significantly different from control. The "competitive inhibition" could thus be ascribed to an isotope-dilution effect. There was no evidence to suggest that NAD caused ADP-ribosylation of the luminal membrane. These studies indicate that adenine and guanine nucleotides do not inhibit P transport by a direct action on the luminal membrane of the proximal tubule but do inhibit lumen-to-bath P flux in isolated perfused proximal tubules at concentrations of 10(-5) M. Since there is no direct inhibitory effect of these compounds at the level of the BBM, it is possible that they inhibit P transport by altering some event subsequent to the transfer of P across the luminal membrane.
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PMID:Nucleotide inhibition of phosphate transport in the renal proximal tubule. 688 41

The objective of the present study was to characterize the interaction between human platelets and vaccinia virus and to examine possible impairment of platelet functions. The vaccinia virus was selected for our model system because it lacks detectable neuraminidase activity. Platelets were incubated with purified viral particles labeled with 3H-thymidine and binding parameters were analyzed. Binding reached saturation with an average of 5 particles/platelet. It was not affected by the plasma but was sensitive to temperature and to metabolic inhibitors. 3H-thymidine-labeled vaccinia virus and formaldehyde-fixed platelets were used to measure viral adsorption. The adsorption was temperature-independent but was affected by ionic strength, indicating electrostatic interactions. Treatment of the fixed platelets with neuraminidase or with alkaline phosphatase reduced viral adsorption, indicating that sialate and phosphate residues on the platelet surface may be involved in the adsorption. Platelet activities were markedly affected by vaccinia virus. The virus caused a dramatic 14C-serotonin release with no added inducer. The release was inhibited by aspirin, a known inhibitor of serotonin release related to prostaglandin synthesis. Furthermore, the virus inhibited platelet aggregation, induced by either ADP, collagen, or thrombin. This study demonstrates that although vaccinia virus lacks neuraminidase activity, it does bind to platelets and affects their function.
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PMID:Interaction between vaccinia virus and human blood platelets. 705 66

The action of 3-[4,5-bis-(4-chlorophenyl)-oxazolyl-(2)-thio]-propionic acid (tioxaprofen, EMD 26 644), a non-steroidal antiinflammatory substance, on platelet function has been studied in vitro and ex vitro. Collagen-induced aggregation and the second phase of adrenaline-induced aggregation are inhibited by small concentrations of tioxaprofen, The ADP-induced aggregation being inhibited only by higher concentrations. The generation of malonedialdehyde (MDA) is blocked. The pathological spontaneous aggregation found by the method of Born was reversed after treatment, and the pathologically increased aggregation according to platelet aggregation test (PAT I) of Breddin was normalized. Tioxaprofen blocks the formation of thromboxane most probably by inhibition of cyclo-oxygenase, but an inhibition of thromboxane synthetase cannot be excluded by our results. The in vivo action starts immediately after ingestion of tioxaprofen and is maintained by small doses. By checking the routine parameters of the blood a slight increase of creatinine and blood urea nitrogen (BUN) and a slight reduction of gamma-GT and alkaline phosphatase were found, all values remaining within the reference interval.
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PMID:[Action of tioxaprofen on platelet function (author's transl)]. 720 7

Extracts of A. niger could catalyze sequential hydrolysis of the three phosphate moieties of the ATP molecule optimally at pH 2 and at pH 8. At pH 2 the hydrolysis was effected by an ATPase followed by acid phosphatase while at pH 8 alkaline phosphatase was the only involved enzyme. Separation of these three phosphate-hydrolyzing enzymes was achieved by Sephadex G-100 column chromatography. The A. niger ATPase seems to have two unique features. First, it was easily solubilized in distilled water and second it had optimum activity at pH 2. The activity of this enzyme was not affected on addition of Na+, K+ or Ca2+ to the assay reaction mixture. It was neither inhibited by sodium azide nor by potassium nitrate but inhibited by orthovanadate, DES, DCCD, Mg2+ and Pi. The substrate concentration-activity relationship was of the hyperbolic type. The enzyme had high specificity for ATP, was inert with ADP and its activity with GTP represented about 6% only of that obtained with equimolar amount of ATP.
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PMID:Participation of a proton-translocating plasma membrane ATPase, acid phosphatase and alkaline phosphatase in ATP degradation by Aspergillus niger extracts. 754 49

Adenosine triphosphate metabolism in caudal epididymis bovine spermatozoa was studied. Measurements by HPLC at appropriate time intervals of the spermatozoa content of ATP and its derivatives were carried out under different experimental conditions. In the presence of 2-D-glucose, cellular ATP was transformed almost quantitatively into ADP and AMP at a rate of 2.3 nmol/min per 10(8) cells. At the same time, ADP and AMP accumulated at a rate of 1.52 and 0.58 nmol/min per 10(8) cells, respectively. In the first 4 min, about 50% of total ATP was degraded, the AEC of the cells dropped to non-physiological values while the content of other nucleosides did not vary significantly. Inorganic P(i) content also remained unchanged. Under non-induced conditions up to 240 min, no variations of the adenylic content and of the EC value was observed. Under induced and non-induced conditions, IMP and adenosine were not detected within the spermatozoa. The lack of IMP might be ascribed either to the absence of AMP deaminase, whose activity has never been found in the spermatozoa or to the intracellular environment which down regulates the activity of the enzyme. In order to explain low levels and absence of variations of adenosine, several enzymic investigations were carried out. Adenosine kinase activity was not determined, therefore the transformation of adenosine into AMP had to be excluded. Nevertheless, enzymic activities potentially able to dephosphorylate the formed AMP are present in the spermatozoa. Our findings are indicative of the existence in the spermatozoa of acid and alkaline phosphatase and of 5'-nucleotidase membrane-derived.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Adenosine triphosphate catabolism in bovine spermatozoa. 758 34

The objective of the investigation was to explore the notion that chondrocytes in the growth plate secrete nucleotides and that these compounds are used to regulate cell maturation and matrix mineralization. Chondrocytes were isolated from the cephalic region of chick embryo sterna and maintained in culture until confluent. To promote expression of the mature phenotype, cultures were then treated with retinoic acid. During the culture period, medium was removed and analyzed for nucleotides using a modified reverse-phase high-performance liquid chromatography (HPLC) procedure. We found that culture medium, conditioned by the chondrocytes, contained significant quantities of nucleotides. Moreover, the nucleotide concentrations were similar in magnitude to levels reported for media conditioned by other cell types. In terms of species, adenosine diphosphate (ADP) was the major nucleotide present in the conditioned medium; adenosine monophosphate (AMP) was present, but at a lower concentration than ADP. To examine the possibility that adenosine triphosphate (ATP) was released by the cultured chondrocytes, but was rapidly degraded into ADP and AMP, we examined the kinetics of ATP breakdown by chondrocytes. We found that chondrocytes degraded over 70% of exogenous ATP within 15 minutes. Similar experiments performed with ADP and AMP indicated that these nucleotides were also degraded by the cells, but at a slower rate than ATP. To determine whether the extracellular nucleotides modulate cartilage development, we examined the effect of exogenous ATP on four major determinants of chondrocyte function: alkaline phosphatase activity, cell proliferation rate, anaerobic metabolism, and mineral deposition. We found that ATP caused only minimum alterations in cell number and alkaline phosphatase activity; however, it increased the lactate content of the medium probably by stimulating anaerobic glycolysis. We noted that ATP had a significant effect on the amount and type of mineral deposited into chondrocyte cultures. Compared with untreated controls, ATP stimulated formation of a small amount of poorly crystallized calcium phosphate. The results of the study show for the first time that chondrocytes release nucleotides into the extracellular milieu. Although they are rapidly degraded, they serve to regulate both mineral formation and energy metabolism.
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PMID:Adenine nucleotide metabolism by chondrocytes in vitro: role of ATP in chondrocyte maturation and matrix mineralization. 759 25


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