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 treatment of human platelets with the dibutyryl cyclic AMP (dbcAMP) revealed the presence of a 250 kDa protein which enhanced its GTP-binding activity. This protein was purified from platelet membranes by successive chromatographies on DEAE-cellulose, Ultrogel AcA34, Mono Q, HCA-hydroxyapatite, and TSK-3000SW columns. The positive cross-reaction of the 250 kDa protein with the anti-filamin antibody indicated that this protein is filamin or very close to it. The GTP gamma S-binding activity of this protein, when phosphorylated with cyclic AMP-dependent protein kinase (A-kinase), showed an over tenfold increase, with the specific activity being 3.6 nmol/mg protein. Dephosphorylation of the phosphorylated protein with alkaline phosphatase reduced the GTP gamma S-binding activity to the control untreated level.
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PMID:Enhancement of GTP gamma S-binding activity by cAMP-dependent phosphorylation of a filamin-like 250 kDa membrane protein in human platelets. 217 20

Bone cells derived from human trabecular explants display osteoblastic features. We examined the modulation of alkaline phosphatase activity and cAMP production as the result of exposing trabecular explants to physiologic concentrations of dexamethasone for 4 weeks during cellular outgrowth and subculture. Cells treated with dexamethasone were observed to grow generally more slowly than control cells. Cells appeared larger and more polygonal, and staining for alkaline phosphatase was more intense in the dexamethasone-exposed cultures. There was a progressive increase in cellular PTH responsiveness with increasing duration of exposure of cells to dexamethasone. Cells grown for 6 weeks in 3 x 10(-8) M dexamethasone had a 10-fold increase in PTH-stimulated cyclic AMP accumulation. Dexamethasone-treated cells also had a significantly increased alkaline phosphatase activity. 1,25-(OH)2D3-stimulated alkaline phosphatase activity was increased approximately 20-fold. cAMP responses were significantly increased to PTH (21.7-fold), PGE1 (2.67-fold), and forskolin (4.81-fold), but not to cholera toxin. Dexamethasone-treated cells also had a mean decrease in 1,25-(OH)2D3-stimulated osteocalcin production to 26.2% of control values (p less than 0.001). Hydrocortisone treatment gave rise to similar effects but of smaller magnitude than those of dexamethasone. Testosterone did not have a significant effect on alkaline phosphatase activity or cAMP production. Skin fibroblasts showed a significant enhancement of alkaline phosphatase activity in response to dexamethasone, but of a much smaller magnitude than in bone cells. The phenotypic changes induced by long-term culture in dexamethasone are consistent with the promotion of a more differentiated osteoblastic phenotype.
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PMID:Long-term effects of physiologic concentrations of dexamethasone on human bone-derived cells. 217 56

The human osteosarcoma cell line MG-63 has been used to study the production of the bone-specific protein, osteocalcin. In the absence of any stimuli, MG-63 cells secreted very low levels of osteocalcin. The secretion of osteocalcin started after a lag time of 10-12 h upon 1,25-(OH)2D3 treatment. Osteocalcin secretion was measured at doses as low as 0.03 nM (fourfold increase, p less than 0.05), and this activity increased further with higher doses of 1,25-(OH)2D3 to reach a plateau at 50 nM. The secretion increased transiently from very low levels in sparse cell cultures to peak values in subconfluent cultures (+/- 40%), two- to threefold above values obtained for confluent cells. Values for confluent cells average 55.9 +/- 2.0 ng/ml protein per 48 h. A similar behavior is observed for 1,25-(OH)2D3 receptor concentration under similar experimental conditions. Bmax increased transiently from sparse to subconfluent cell cultures (40-60% confluent) and reached values 50% lower in confluent cells. However, the receptor affinity was not affected by cell density. MG-63 cells also possessed an alkaline phosphatase isoenzyme of the bone-liver-kidney type that was stimulated by 1,25-(OH)2D3 treatment (two- to threefold) and inhibited by parathyroid hormone (40 nM, -25%, p less than 0.025). PTH and PGE2 increased cAMP production in a dose-dependent manner, but the cells were irresponsive to salmon calcitonin. Basal and PTH-responsive cyclic AMP production were also modulated by cell density. Dexamethasone pretreatment (100 nM, 48 h) stimulated the PTH-dependent cAMP production but failed to influence the response to PGE2.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Osteocalcin secretion by the human osteosarcoma cell line MG-63. 217 53

1. Activity of "high Km" 5'-nucleotidase was investigated in the soluble fractions from cultured human T- and B-lymphoblasts. 2. Using gel filtration chromatography and 5'-AMP-Sepharose 4B affinity chromatography, it separated high Km 5'-nucleotidases from other two different soluble nucleoside 5'-phosphomonoesterase activities. 3. The molecular mass of the high Km enzymes from T- and B-lymphoblasts were 210 and 200 kDa, respectively. The optimum pH was at 6.5, and the Km values for IMP and AMP were 0.4 and 0.9 mM, respectively. 4. These properties of high Km 5'-nucleotidases were similar to those previously described from different tissues. These data indicate that soluble high Km 5'-nucleotidase coexists with "low Km" enzyme.
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PMID:Soluble "high Km" 5'-nucleotidase activity in human T- and B-lymphoblasts: isolation and some properties. 225 52

Previous results demonstrated that the adenosine that accumulates in human fat cell suspensions is derived from extracellular sources (Kather, H. (1988) J. Biol. Chem. 263, 8803-8809). To get insight into the mechanisms responsible for the lack of adenosine release, extracellular adenine nucleotide catabolism was minimized by 10 mmol/liter beta-glycerophosphate and 10 mumol/liter alpha,beta-methyleneadenosine 5'-diphosphate. Intracellular adenine nucleotide catabolism resulted in a release of inosine and hypoxanthine under these conditions that was increased markedly by isoproterenol. Experiments with inhibitors of adenosine deaminase and adenosine kinase indicated that the production of inosine and hypoxanthine proceeded via AMP deamination. Consistently, IMP levels were increased transiently in the presence of isoproterenol. In addition, the cells possessed a nucleotide phosphomonoesterase that was resistant to the inhibitory actions of ATP and alpha,beta-methyleneadenosine 5'-diphosphate and showed preference for IMP over AMP. Adenosine (approximately 1 nmol/10(6) cells/h) was also produced inside the cells. However, adenosine production was unrelated to ATP turnover via adenylate cyclase, and any adenosine formed was immediately reconverted to adenine nucleotides in the absence and presence of isoproterenol. It was concluded that adenosine is not released by intact human adipocytes, because the alternative routes of intracellular AMP catabolism are compartmentalized (at least in functional terms), and adenosine kinase is not saturated with substrate in the absence and presence of isoproterenol.
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PMID:Pathways of purine metabolism in human adipocytes. Further evidence against a role of adenosine as an endogenous regulator of human fat cell function. 229 25

Lack of adequate data concerning the effect of age on biochemical variables relating to bone and mineral metabolism hampers research on age-related bone loss in women. Furthermore, to detect disease and to monitor therapy, clinical laboratories require reference values derived from an appropriate population sample. Therefore, we determined the age-specific distribution of values for serum concentrations of calcium, inorganic phosphorus, alkaline phosphatase, bone Gla protein, and parathyroid hormone; for creatinine clearance; for fasting urinary calcium:creatinine ratio; and for 24 h urinary excretion of calcium, hydroxyproline, and cyclic AMP in a population-based sample of 301 white women. From this sample, a healthy subgroup of 181 women was identified by medical record review. Age-related effects were seen in all variables except serum calcium and phosphorus. Moreover, substantial differences between the population sample and the healthy subgroup were noted in values for creatinine clearance, serum alkaline phosphatase, and 24 h urinary calcium excretion. These observations may prove useful for assessment of normality in other populations of aging white women.
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PMID:Effect of age on variables relating to calcium and phosphorus metabolism in women. 234 74

The calcium (Ca) metabolism of established human lactation was studied in 40 adult women (mean age 32.4 years) who had been breast-feeding for 6 months (Lac) and in 40 age-matched controls (Con) using fasting urine and blood biochemistry and forearm single-photon bone mineral densitometry (BMD). Serial studies were performed up to 6 months after weaning in Lac women and repeated once in Con women. During lactation the significant findings were (1) a selective reduction (7.1%, P less than 0.03) in BMD at the ultradistal site containing 60% trabecular bone, but not at two more proximal, chiefly cortical bone sites; (2) increased bone turnover affecting bone resorption [fasting hydroxyproline excretion, Lac 2.22 +/- 0.12 mumol/liter GF (mean +/- SEM), Con 1.19 +/- 0.04, P less than 0.001] and affecting bone formation (plasma alkaline phosphatase, Lac 81.9 +/- 2.5 IU/liter, Con 53.5 +/- 2.7, P less than 0.001, and serum osteocalcin, Lac 14.0 +/- 0.7 microgram/liter, Con 7.3 +/- 0.4, P less than 0.001); and (3) renal conservation in the fasting state of both Ca and inorganic phosphate (Pi) with a resultant moderate increase in plasma Pi but not in plasma Ca (total or ionized). There were no differences between the groups in serum parathyroid hormone (PTH, intact and midmolecule assays), 25-hydroxy- and 1,25-dihydroxyvitamin D, nephrogenous cyclic AMP production, or plasma creatinine.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Human lactation: forearm trabecular bone loss, increased bone turnover, and renal conservation of calcium and inorganic phosphate with recovery of bone mass following weaning. 234 75

Alkaline phosphatase activity in rat hepatoma cells (R-Y121B) cultured in a monolayer at 0.5% serum was enhanced by serum, bovine serum albumin, casein and gamma-globulin, but ovalbumin, polyvinylpyrrolidone, dexamethasone, insulin and dibutyrylcyclic AMP showed little effect on alkaline phosphatase activity. In addition, cycloheximide, actinomycin D, chloroquine, dinitrophenol and potassium cyanide also increased the enzyme activity, although the incorporation of [14C]leucine into cellular proteins was almost completely inhibited in the presence of these cytotoxic substances. When R-Y121B cell homogenates were incubated at 37 degrees C, alkaline phosphatase activity increased in a pH-dependent manner: the maximal increase was observed at pH 7.1. The magnitudes of the increase differed among cell homogenates and a 4- to 10-fold increase was observed. Alkaline phosphatase in R-Y121B cells was apparently heat-stable, but that in the cells obtained from various treatments was heat labile and the latter activity decreased to less than 50% of the initial activity after 15 min of incubation at 56 degrees C. Alkaline phosphatase in the control and also in the treated cells was more sensitive to L-homoarginine than L-phenylalanine. The Lineweaver-Burk plot showed that the increases in the enzyme activity were accompanied by changes not only in V but also in Km for alkaline phosphatase reaction. Finally, it has been suggested that the increases in alkaline phosphatase activity under various conditions are due to the conversion of the molecule with a low enzyme activity to the molecule with a high enzyme activity in R-Y121B cells.
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PMID:Regulation of alkaline phosphatase activity in rat hepatoma cells. Effects of serum proteins, cycloheximide, actinomycin D, chloroquine, dinitrophenol and potassium cyanide. 241 85

Micrococcal nuclease treatment of the native adenylylated glutamine synthetase from M. smegmatis yielded adenosine and phosphotyrosyl enzyme. The rate of the deadenosylation reaction was monitored by the appearance of the adenosine in HPLC analysis. The o-phosphotyrosyl enzyme had catalytic activity comparable to that of the adenylylated enzyme suggesting that the adenosine part in AMP was not essential to the regulation of the enzyme activity. Further, upon treatment of the phosphotyrosyl enzyme with alkaline phosphatase, the glutamine synthetase activity was increased. This means that the regulation site of glutamine synthetase by covalent modification simply requires the phosphorylation of the tyrosine residue.
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PMID:The conversion of native adenylylated glutamine synthetase into phosphotyrosine enzyme by micrococcal nuclease. 242 3

In rat osteosarcoma (ROS 17/2.8) cells, which express osteoblastic features in culture, basic fibroblast growth factor (bFGF) reduces the level of alkaline phosphatase, type I collagen, and osteocalcin mRNA and increases osteopontin mRNA, independent of growth stimulation. The fibroblast growth factor (FGF) effects are dose dependent (EC50 about 6 pM) and are detected 24 h after addition of the growth factor. bFGF also reduces parathyroid hormone-stimulatable adenylate cyclase and alkaline phosphatase activity in these cells. Concomitant treatment with pertussis toxin (20 ng/ml) opposes the FGF effects. Although cyclic AMP elevating agents mimic pertussis toxin action on some parameters, they produce opposite effects on others, indicating that antagonism between pertussis toxin and bFGF is not mediated by cyclic AMP. bFGF caused a small reduction in steady state NAD-dependent ADP-ribosylation and had no detectable effects on the steady-state levels of the Gi alpha (alpha subunit of the inhibitory G protein) 1, 2, and 3, visualized with specific antibodies in these cells. Although the site of interaction of pertussis toxin and FGF remains to be determined, the findings presented here suggest separate control of growth and differentiation by bFGF and show that pertussis toxin treatment can modulate differentiation in these cells, presumably via Gi proteins.
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PMID:Opposing effects of fibroblast growth factor and pertussis toxin on alkaline phosphatase, osteopontin, osteocalcin, and type I collagen mRNA levels in ROS 17/2.8 cells. 247 40


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