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 rabbit iris smooth muscle has been shown to contain triphosphoinositide phosphomonoesterase (phosphatidyl-myo-inositol-4,5-bisphosphate phosphohydrolase, EC 3.1.3.36) and phosphodiesterase (triphosphoinositide inositoltrisphosphohydrolase, EC 3.1.4.11) activities. Under our experimental conditions about 77% of the phosphomonoesterase and 61% of the phosphodiesterase activities were localized in the particulate fraction. The kinetic properties of the enzymes in the microsomal fraction were examined. The enzyme preparation was specific to polyphosphoinositides; it did not attack phosphatidylinositol under the present assay condition. The effects of Ca2+ and Mg2+ were also studied. Although the microsomal enzymes did not require added divalent cations for their activities, both the phosphomonoesterase and phosphodiesterase were appreciably inhibited by 1 mM EDTA. Phosphodiesterase and phosphomonoesterase were stimulated by Ca2+ and Mg2+, respectively. The demonstration of triphosphoinositide phosphodiesterase in the iris muscle, coupled with the findings that this enzyme is activated by Ca2+ and is not influenced by acetylcholine add further support to our previous conclusion (J. Pharmacol. Exp. Ther. (1978) 204, 655--668; J. Neurochem. (1978) 30, 517--525) that an increased Ca2+ influx, following the interaction between the neurotransmitter and its receptor, could act to stimulate the phosphodiesterase, thus leading to increased triphosphoinositide breakdown and increased phosphatidic acid via increased diacylglycerol.
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PMID:Studies on the properties of triphosphoinositide phosphomonoesterase and phosphodiesterase of rabbit iris smooth muscle. 21 33

Phosphatidylinositol 4-phosphate (PIP) kinase (E.C. 2.7.1.68) has been purified about 1200-fold from rat liver plasma membranes, taking advantage of affinity chromatography on quercetin-Sepharose as a novel step. The purified PIP kinase showed no contamination by the following enzyme activities: phosphatidylinositol (PI) kinase (EC 2.7.1.67), protein kinase C (EC 2.7.1.-), diacylglycerol kinase (EC 2.7.1.-), phospholipase C (EC 3.1.4.11), protein-tyrosine kinase (EC 2.7.1.112), alkaline phosphatase (EC 3.1.3.1), triphosphoinositide phosphomonoesterase (EC 3.1.3.36), adenylate kinase (EC 2.7.4.3) and cAMP-dependent protein kinase (EC 2.7.1.37). The liver membrane enzyme requires high Mg2+ concentrations with a KM value of 10 mM. Ca2+ or Mn2+ could replace Mg2+ to a certain, though small, extent. Apparent KM values with respect to PIP and ATP were 10 and 65 microM, respectively. GTP was slightly utilized by the kinase as phosphate donor while CTP was not. Quercetin inhibited the enzyme with Ki = 34 microM. Extending our previous observations (Urumow, T. and Wieland, O.H. (1986) FEBS Lett. 207, 253-257 and Urumow, T. and Wieland, O.H. (1988) Biochim. Biophys. Acta 972, 232-238) [gamma S]pppG still stimulated the PIP kinase in extracts of solubilized liver membranes. 20-40% (NH4)2SO4 precipitation of the membrane extracts yielded a fraction that contained the bulk of enzyme activity but did not respond to stimulation by [gamma S]pppG any longer. This was restored by recombination with a protein fraction collected at 40-70% (NH4)2SO4 saturation, presumably containing a GTP binding protein and/or some other factor separated from the PIP kinase. In the reconstituted system [gamma S]pppG stimulated PIP kinase in a concentration dependent manner with maximal activation at 5 microM. This effect was not mimicked by [gamma S]pppA and was blocked by [beta S]ppG. These results strongly support our view that in liver membranes PIP kinase is regulated by a G-protein.
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PMID:Purification and partial characterization of phosphatidylinositol-4-phosphate kinase from rat liver plasma membranes. Further evidence for a stimulatory G-protein. 215 97

1. Some properties of the triphosphoinositide phosphomonoesterase from the homogenates of guinea-pig brain were studied. The enzyme has an optimum pH range 6.7-7.3, is stimulated with KCl at a concentration of 0.1m, and under these conditions has K(m)1.43x10(-4)m. 2. A factor from the ;pH5 supernatant' of guinea-pig brain stimulates the enzyme activity over and above the stimulation produced by KCl. Subcellular fractions of guinea-pig brain varied in their response to the ;pH5 supernatant'. Maximum stimulation was observed with the P(1) fraction, containing myelin and nuclei. 3. An assay system for the enzyme was developed that contained optimum concentrations of both KCl and the ;pH5 supernatant'. Acid phosphatases were inhibited by NaF, but, in contrast with previous work, no EDTA was added to the assay system to inhibit the alkaline phosphatases. This reagent inhibited the triphosphoinositide phosphomonoesterase. It was estimated that the remaining fraction of non-specific phosphatases can account for only 14% of the observed triphosphoinositide phosphomonoesterase activity. 4. Subcellular fractions of guinea-pig brain were characterized by electron microscopy and subcellular markers. The triphosphoinositide phosphomonoesterase exhibited a distribution between the fractions similar to that of 5'-nucleotidase, but different from that of alkaline phosphatase.
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PMID:The subcellular distribution of triphosphoinositide phosphomonoesterase in guinea-pig brain. 434 4

Incubation of rat liver nuclear envelopes with [gamma-32P]ATP resulted in the synthesis of phosphatidylinositol-[4-32P]phosphate (PIP). Degradation of endogenously labeled PIP was observed upon the dilution of the labeled ATP with an excess of unlabeled ATP. This degradation was most rapid in the presence of EDTA, and was inhibited by MgCl2 and CaCl2. To further characterize the degradative activity, phosphatidylinositol[4-32P]phosphate and phosphatidylinositol [4,5-32P]bisphosphate (PIP2) were synthesized and isolated from erythrocyte plasma membranes. The 32P-labeled phospholipids were then resuspended in 0.4% Tween 80, a detergent that did not inhibit degradation of endogenously labeled PIP, and mixed with nuclear envelopes. [32P]PIP and [32P]PIP2 were degraded at rates of 2.25 and 0.04 nmol min-1 mg nuclear envelope protein-1, respectively. Only 32P was released from phosphatidyl[2-3H]inositol-[4-32P]phosphate, indicating that hydrolysis of PIP was due to a phosphomonoesterase activity (EC 3.1.3.36) in nuclear envelopes. Similarly, anion-exchange chromatographic analysis of the water-soluble products released from [32P]PIP indicated that inorganic phosphate was the sole 32P-labeled product. Hydrolysis of PIP was most rapid at neutral pH, and was not affected by inhibitors of acid phosphatase or alkaline phosphatase. Hydrolysis of PIP was also not inhibited by nonspecific phosphatase substrates, such as glycerophosphate, p-nitrophenylphosphate, AMP, or glucose 6-phosphate. Hydrolysis was stimulated by putrescine, and was inhibited by inositol 2-phosphate, spermidine, spermine, and neomycin.
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PMID:Characterization of a phosphatidylinositol 4-phosphate-specific phosphomonoesterase in rat liver nuclear envelopes. 609 90