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 anabolic effect of 17beta-estradiol in osteoblastic MC3T3-E1 cells was investigated. The cells were cultured for 3 days in the medium containing either vehicle or 17beta-estradiol (10(-11)-10(-9) M). 17beta-Estradiol significantly increased alkaline phosphatase activity and protein concentration in the cells. The steroid (10(-9) M) also significantly elevated the cell numbers and the cellular DNA content. The anabolic effect by 17beta-estradiol was blocked by the presence of dipicolinate (10(-3) M), a chelator of zinc ion, suggesting a role of cellular zinc in osteoblastic cell function. The presence of zinc sulfate (10(-5) M) or beta-alanyl-L-histidinato zinc (AHZ) (10(-5) M) significantly enhanced the 17beta-estradiol (10(-10) or 10(-9) M)-induced increase of alkaline phosphatase activity and protein concentration in the cells; the effect of AHZ was greater than that of zinc sulfate. The enhancement by zinc compounds was not based on the augmentation of osteoblastic cell numbers. The co-addition of cycloheximide (10(-6) M), an inhibitor of protein synthesis, completely blocked the zinc compound (10(-5) M)-induced enhancement of 17beta-estradiol's (10(-9) M) effect to increase alkaline phosphatase activity and protein concentration in the cells. Moreover, the anabolic effect of 17beta-estradiol together with or without zinc compounds was abolished by the presence of staurosporine (10(-8) M), an inhibitor of protein kinase C, or of okadaic acid (10(-7) M), an inhibitor of protein phosphatase. The present study demonstrates that the anabolic effect of 17beta-estradiol is enhanced by zinc-chelating dipeptide in osteoblastic MC3T3-E1 cells, and that the enhancing effect may involve protein synthesis and protein kinase activity.
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PMID:Zinc enhancement of 17beta-estradiol's anabolic effect in osteoblastic MC3T3-E1 cells. 916 27

Orthovanadate is a known inhibitor of phosphotyrosyl protein phosphatase and is reported to stimulate osteogenic cell proliferation and differentiation when administered during the logarithmic growth phase and to potentiate the mitogenic effects of several growth factors. There is little information concerning the effects of orthovanadate on bone matrix deposition and mineralization, although there is some evidence that it increases collagen synthesis by osteogenic cells. To test the effects of orthovanadate on bone nodule formation and mineralization, osteogenic cells were exposed to 5-50 microM orthovanadate or 10(-7) M insulin-like growth factor-1 for 3, 7, and 21 days after plating. Exposure to orthovanadate produced differential effects on cellular proliferation and alkaline phosphatase activity following completion of the logarithmic growth phase, and on resultant bone nodule formation and mineralization by these populations. The effects of orthovanadate on osteogenic cultures were concentration dependent: 5 microM concentrations produced by a relatively large quantity of poorly mineralized matrix, while 30-50 microM concentrations produced a smaller quantity of heavily mineralized matrix. Thus, orthovanadate could possibly be used as a growth factor for bone, if administered at the critical dosage at the proper stage of the life cycle of the osteoblast.
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PMID:Enhancement by sodium orthovanadate of the formation and mineralization of bone nodules by chick osteoblasts in vitro. 922 45

Here we show that brain-derived neurotrophic factor (BDNF) stimulates both the phosphorylation of the Ca2+/calmodulin-dependent protein kinase 2 (CaMK2) and its kinase activity in rat hippocampal slices. In addition, we find that: (i) the time course of BDNF action is not accompanied by a change in the spectrum of either alpha- and beta-subunits of CaMK2 detected by immunoblotting; (ii) both treatment of solubilized CaMK2 with alkaline phosphatase and treatment of immunoprecipitated CaMK2 with protein phosphatase 1 reverse phosphorylation and activation of the kinase; (iii) phospholipase C inhibitor D609 and intracellular Ca2+ chelation by 1,2-bis-(o-aminophenoxy)ethane-N,N,N",N',-tetracetic acid tetra(acetoxymethyl)ester or 8-(diethylamino)octyl-3,4,5-trimethoxybenzoate but not omission of Ca2+ or Ca2+ chelation by EGTA, abolish the stimulatory effect of BDNF on phosphorylation and activation of CaMK2. These results strongly suggest that the conversion of CaMK2 into its active, autophosphorylated form, but not its concentration, is increased by BDNF via stimulation of phospholipase C and subsequent intracellular Ca2+ mobilization.
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PMID:Brain-derived neurotrophic factor increases Ca2+/calmodulin-dependent protein kinase 2 activity in hippocampus. 930 59

Annexins are a family of calcium-binding proteins that have been implicated in a wide range of intracellular processes. We have previously reported that stimulation of platelets with agents that increase intracellular [Ca2+] induces the relocation of annexin V to membranes, and that this annexin V may be binding to a 50 kDa protein located within platelet membranes. We report here, using an in vitro reconstitution system, that the relocation of annexin V to membranes is enhanced by ATP. We also demonstrate that when adenosine 5'-[gamma-thio]-triphosphate, which can replace ATP in phosphorylation reactions, is substituted for ATP, the amount of annexin V that binds to membranes is further increased. In separate experiments using intact cells, we show that the protein phosphatase inhibitor okadaic acid mimics the action of the physiological agonist thrombin, in that it induces annexin V to bind to membranes and that the addition of the protein kinase inhibitor staurosporine inhibits A23187-induced relocation of annexin V. In addition, alkaline phosphatase, when added to isolated membranes, was found to remove endogenous annexin V from the membranes. Furthermore, immunoprecipitation of 33P-labelled proteins indicated that annexin V may form a multi-protein complex including phosphoproteins of 25, 50 and 83 kDa. Taken together these observations suggest that, following physiological activation, the phosphorylation of one or more proteins is responsible for the tight association of annexin V with platelet membranes and the subsequent regulation of membrane localized processes.
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PMID:Relocation of annexin V to platelet membranes is a phosphorylation-dependent process. 937

An acid phosphatase from a heavy-metal-accumulating strain of a Citrobacter sp. was resolved into two forms on the basis of their nonbinding (phosphatase I) or binding (phosphatase II) behaviour on the cation-exchange resin SP-Sephadex C50. Both holoenzymes had a molecular mass of 103-108 kDa as determined by Superose Q-6 column chromatography in the presence of 150 mM KCl and a subunit molecular mass of 27 kDa as determined by SDS-PAGE; the enzyme was tetrameric. Both enzymes had a pI approximately 9.0 and were immunologically cross-reactive. There were minor differences in amino acid composition and in peptide maps following tryptic digest. The pH optimum for phosphatases I and II was 5.5 and 6.25, respectively; phosphatase II alone retained activity at pH values up to 9.0. Phosphatase I was more resistant to mechanical shear, gamma-irradiation, high temperature, and toxins (F- and formaldehyde). Glycerol increased the thermostability of both enzymes, particularly the more thermosensitive phosphatase II. Phosphatase II had a lower Km and a lower Vmax for glycerol 2-phosphate hydrolysis. The production of enzyme isoforms is a phenomenon similar to that described previously for the alkaline phosphatase of Escherichia coli, where the isoforms relate to precursive and final processed forms of the enzyme. Acid phosphatase is physiologically distinct, with a role that is still obscure but that may relate to cellular stress responses.
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PMID:Purification and characterization of acid-type phosphatases from a heavy-metal-accumulating Citrobacter sp. 944 88

In this paper, specific PHO13 alkaline phosphatase from Saccharomyces cerevisiae was demonstrated to possess phosphoprotein phosphatase activity on the phosphoseryl proteins histone II-A and casein. The enzyme is a monomeric protein with molecular mass of 60 kDa and hydrolyzes p-nitrophenyl phosphate with maximal activity at pH 8.2 with strong dependence on Mg2+ ions and an apparent Km of 3.6 x 10(-5) M. No other substrates tested except phosphorylated histone II-A and casein were hydrolyzed at any significant rate. These data suggest that the physiological role of the p-nitrophenyl phosphate-specific phosphatase may involve participation in reversible protein phosphorylation. 1988 Federation of European Microbiological Societies.
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PMID:A specific alkaline phosphatase from Saccharomyces cerevisiae with protein phosphatase activity. 956 42

We have found that modification of rat PC12 cells with pertussis toxin resulted in an approximately 50% inhibition of a protein phosphatase 2A-like phosphatase. Protein phosphatase 2A (PP2A) is a major cellular serine/threonine-specific protein phosphatase. Treatment of extracts from pertussis toxin-modified PC12 cells with either immobilized alkaline phosphatase or Ca2+ reversed this inhibition. Reactivation of the PP2A-like phosphatase in Ca2+ appears to result from the dephosphorylation of a protein by the Ca2+/calmodulin-dependent protein phosphatase calcineurin. The PP2A-like phosphatase in extracts from pertussis toxin-modified PC12 cells eluted from a Mono Q column at a higher ionic strength than did the PP2A-like phosphatase in extracts from control cells. After incubation in Ca2+, the PP2A-like phosphatase in extracts from pertussis toxin-modified cells eluted from a Mono Q column at the same ionic strength as did the PP2A-like phosphatase in extracts from control cells. These results indicate that the effect of pertussis toxin on this PP2A-like activity results from the phosphorylation of either one of the subunits of the PP2A-like phosphatase or a protein that when phosphorylated binds to and inhibits this phosphatase. Pertussis toxin modification did not result in the phosphorylation of the catalytic subunit of PP2A. Because phosphorylation regulates the activities of many enzymes and cell surface receptors, a pertussis toxin-induced decrease in PP2A activity could alter signaling pathways and other cellular processes in which G proteins are not directly involved.
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PMID:Pertussis toxin modification of PC12 cells inhibits a protein phosphatase 2A-like phosphatase. 964 72

The purpose of this study was to relate dose-dependent hepatotoxicity stemming from prolonged exposure to sublethal concentrations of the cyclic heptapeptide microcystin-LR (Mcyst) to hepatic Mcyst concentrations and protein phosphatase activity. Mcyst is a potent inhibitor of protein phosphatase types 1 and 2A (PP1 and PP2A). Twenty male Sprague-Dawley rats were infused continuously with 0, 3, 6, or 9 micrograms Mcyst/day for 28 days using intraperitoneal mini-osmotic pumps containing highly purified toxin or saline. At the end of 28 days, dose-dependent increases in several serum biochemical tests including sorbitol dehydrogenase, aspartate aminotransferase, gamma-glutamyl transferase, alkaline phosphatase, and bile acids had occurred. Serum albumin decreased in a dose-dependent fashion. Liver activity of both PP1 and PP2A decreased in a dose-dependent manner, but with a relatively greater effect on PP2A than PP1. Liver cytosol Mcyst concentrations, measured by direct competitive ELISA, also increased in a dose-dependent manner, although at a higher rate than would be predicted from the incremental increase in dose given. This disproportional increase is suggestive of the bioaccumulation of Mcyst with increasing dose. Histopathological abnormalities included hepatocellular apoptosis and cytosolic vacuolation of principally zone 3 hepatocytes. Immunohistochemical stains revealed Mcyst predominantly within pericanalicular regions of zone 3 hepatocytes. It was concluded that prolonged exposure to sublethal concentrations of Mcyst results in multiple dose-dependent hepatotoxic effects that correspond to decreased hepatic serine/threonine protein phosphatase activity and increasing cytosolic Mcyst concentrations. The disproportional increase of hepatic Mcyst concentrations observed may suggest the bioaccumulation of toxin and an increasing relative risk of hepatotoxicity with increasing dose.
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PMID:Prolonged sublethal exposure to the protein phosphatase inhibitor microcystin-LR results in multiple dose-dependent hepatotoxic effects. 972 Jan 45

A low molecular weight mitogen (LMP) from Streptococcus pyogenes strain NY 5 was successively purified by adsorption on phenylsepharose, chromatography on Resource S and Superdex G 30 and finally by affinity chromatography on antiphosphothreonine agarose. The N-terminal protein sequence of the mitogen was determined. The occurrence of phosphoamino acids was investigated by immunoassay using monoclonal antibodies. The LMP is a threonine-phosphorylated protein different of HPR protein of PTS-system, its mitogenic activity was lost after treatment with streptococcal protein phosphatase or alkaline phosphatase. The inactivated LMP was activated by phosphorylation with phosphokinase and ATP. The active LMP was also inactivated in streptococcal cultures secreting acid protein phosphatase during the phase of phosphate limitation.
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PMID:Influence of the phosphorylation state on the biological activity of a low-molecular mitogen from group A streptococci. 972 1

The binding of aldosterone (ALDO) to the mineralocorticoid receptor (MR) induces a conformational change of the protein referred to as 'transformation'. This feature can be evidenced in vivo by the capacity of the MR to interact with chromatin, and in vitro by the ability of the MR to bind to DNA strands or to shift the sedimentation coefficient (S) to lower values. The transformation process allows MR to work as a transcription factor after interacting with specific sequences of DNA. The signal transduction pathway for the MR transformation remains unknown. As a first step towards elucidating the mechanism of steroid-dependent MR transformation, we asked if the MR-signaling pathway is affected by the phosphorylation status of the MR-heterocomplex, and how that pathway may be regulated. Incubation of preformed [3H]ALDO-MR complex with bovine intestinal alkaline phosphatase led to an increase in the rate of MR-transformation (measured as 9.4-5.4S shift). This alkaline phosphatase-dependent MR transformation was inhibited by the specific alkaline phosphatase-type inhibitor levamisole, and was not evident in incubations performed with acid phosphatases. A direct correlation between the DNA-cellulose binding capacity of the [3H]ALDO-MR complex and the percentage of transformed 5.4S MR form was also observed. When rat kidney cytosol was incubated in the absence of both exogenous phosphatase and stabilizing agents (such as molybdate or vanadate), MR transformation also took place, in a time- and temperature-dependent process. In contrast with the inhibitory effect observed upon alkaline phosphatase-promoted transformation, levamisole was unable to inhibit the endogenous transforming activity of MR, suggesting that an endogenous phosphatase other than those which belong to the alkaline-type may be responsible for that transformation. Tautomycin, a polyketide produced by the soil bacteria Streptomyces which inhibits serine/threonine phosphatases of the PP1/PP2A subgroup, was able to inhibit the endogenous phosphatase activity in a concentration-dependent form (Ki(app)=7.35 nM). These results support the idea that the endogenous renal activity involved in the regulation of rat kidney MR transformation may be a protein phosphatase which belongs to the PP1/PP2A subgroup.
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PMID:Tautomycin inhibits phosphatase-dependent transformation of the rat kidney mineralocorticoid receptor. 986 32


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