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)

Three distinct 5'-phosphomonoesterase activities were isolated from soluble fractions of human placenta, cultured human T and B lymphoblasts, and rat liver using 5'-AMP-sepharose 4B affinity chromatography. We define these activities as "low-Km" 5'-nucleotidase, "high-Km" 5'-nucleotidase, and nonspecific phosphatase. High-Km 5'-nucleotidase was eluted with 0.5 M NaCl, low-Km 5'-nucleotidase was eluted with 10 mM ADP, and nonspecific phosphatase was not retained on the column. We have found significant variability in the relative content of high- to low-Km activities in the tissues studied with the ratios ranging from 5.5 to 264. The properties were studied after further purification. The molecular mass of the low-Km enzymes ranged from 72.5 to 209 kDa, optimum pH ranged from 7.4 to 9.0, Km for AMP ranged from 7 to 15 microM, and Km for IMP ranged from 10 to 26 microM. The molecular mass of the high-Km enzymes ranged from 182 to 210 kDa, pH optimum was at 6.5, Km for AMP ranged from 3.0 to 9.4 mM, and the Km for IMP ranged from 0.3 to 0.5 mM. The data indicate that the soluble low- and high-Km 5'-nucleotidase coexist in the mammalian cells and tissues studied. These observations suggest a complex system for the regulation of nucleoside 5'-monophosphate dephosphorylation.
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PMID:AMP and IMP dephosphorylation by soluble high- and low-Km 5'-nucleotidases. 253 71

We report the characterization of human osteoblastic cells that were derived from the surface of trabecular bone fragments. After removal of bone marrow cells, the bone lining osteoblastic cells lining the bone surface were obtained by migration and proliferation from the trabecular surface onto a nylon mesh. The isolated population proliferated in culture and exhibited osteoblastic phenotype. Cultured cells show a regular arrangement in vitro and exhibited multiple interconnecting junctions on scanning electron microscopic examination. Immunocytochemical staining showed that the cells produced almost exclusively type I collagen. Bone-surface-derived cells responded to 1-34 human parathyroid hormone by increasing intracellular cyclic AMP. Cell cultures exhibited high alkaline phosphatase activity, which was unaffected by 1,25 (OH)2 vitamin D. Untreated cells produced high levels of osteocalcin, a bone-specific protein, and they responded to 1,25(OH) vitamin D by increasing osteocalcin synthesis in a dose-dependent manner. Although cells cultured for up to 5 mo. still produced osteocalcin, the response to 1,25(OH)2D decreased after multiple passages. This study shows that the bone cell populations isolated from trabecular bone surfaces are enriched in osteoblast precursors and mature osteoblastic cells.
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PMID:Culture and behavior of osteoblastic cells isolated from normal trabecular bone surfaces. 254 Nov 29

The studies presented in this report describe an initial characterization of cell types derived from explants of human periodontia. Cell cultures were established from human periodontal ligament (PL4, PL7), gingival tissue (GF2), and alveolar bone (BP1) by means of explant techniques and monolayer culture. Cells were studied at passage numbers 2-4 and were characterized on the basis of morphological, biochemical, and proliferative parameters. Subconfluent cells did not have distinct morphologies useful in distinguishing them from one another. At confluence, PL4 and BP1 cells formed multilayered cultures of randomly oriented cells, while PL7 and GF2 cells grew in a monolayer of parallel cells. Biochemically, PL4 and BP1 cells exhibited characteristics consistent with an osteoblast-like phenotype. These included a significant increase in PTH-stimulated cyclic AMP and high basal levels of alkaline phosphatase activity, which were decreased on exposure to PTH and increased after stimulation by 1.25 dihydroxyvitamin D3. In contrast, PL7 and GF2 cells exhibited basal alkaline phosphatase levels that were low, and cyclic AMP levels were not modulated by PTH stimulation. Cell populations PL7 and GF2 did not proliferate in culture medium supplemented with 3% platelet-poor plasma. After the addition of platelet-derived growth factor (PDGF) to this medium, the proliferation of these cell populations was equal to that in media supplemented with 10% fetal bovine serum. In contrast, PL4 and BP1 cells did proliferate in culture medium supplemented with 3% platelet-poor plasma. The addition of PDGF to the medium resulted in only a moderate increase in the proliferation of cell populations PL4 and BP1.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Initial characterization of cells derived from human periodontia. 254 Nov 86

Proximal tubules were prepared from rat kidney cortex by collagenase digestion and purified by Percoll gradient centrifugation. Their enrichment was estimated by comparing the specific activities of various cell-specific enzymes in homogenates of renal cortex and of the isolated tubules. The tubules were cultured in a 50:50 mixture of Dulbecco's modified Eagle's and Ham's F12 media supplemented with insulin, transferrin, epidermal growth factor, hydrocortisone, and prostaglandin E1. After 2 to 3 d an extensive outgrowth of epithelial cells developed from the attached tubules. After 5 to 7 d near confluent monolayers were obtained. Hormonal responsiveness, marker enzyme activities, and transport properties were determined to further characterize the primary cultures. The cultured cells exhibited increased cyclic AMP production in response to parathyroid hormone but not calcitonin or vasopressin, consistent with the absence of cells derived from distal and collecting tubules. The cells also retained significant levels of 25-hydroxyvitamin D3-1 alpha-hydroxylase, alkaline phosphatase, and gamma-glytamyl-transpeptidase, three enzymes that are primarily associated with the proximal tubule. The cultured epithelial cells also exhibit a Na+-dependent phosphate and glucose transport systems. Therefore, the cells retain many functional properties that are characteristic of proximal tubules. Thus, the primary cultures should be suitable for the study of processes that occur specifically within this segment of the rat nephron.
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PMID:Characterization of primary cell cultures derived from rat renal proximal tubules. 254 89

Three clonal cell lines with differences in responsiveness to parathyroid hormone (PTH), alkaline phosphatase activity, and ability to produce an endothelial cell growth inhibitor(s) during more than 3 years, more than 58 passages, in culture were established from growth cartilage (GC) of mouse ribs. In sparse cultures the three clonal cell lines, MGC/T1.4, MGC/T1.17, and MGC/T1.18, all showed fibroblast-like morphology. However, as they became confluent, MGC/T1.4 cells became polygonal and then multilayered. MGC/T1.18 cells also became polygonal, but showed contact inhibition. MGC/T1.17 cells remained fibroblastic in confluent cultures and formed nodules when cultured for more than 7 days after they became confluent. These nodules calcified in the presence of beta-glycerophosphate. Glycosaminoglycan (GAG) synthesis in the parent uncloned line, MGC/T1 cells, at early passages was about 50-75% of that of primary cultures of mouse GC cells. The GAG syntheses in the three clonal lines were much lower than that of primary cultures of GC cells. Moreover, the sizes of proteoglycan monomers synthesized by these cells were not the same as that of cartilage-specific proteoglycan. The three clonal lines mainly synthesized type I collagen. PTH increased the intracellular cyclic AMP level in MGC/T1, MGC/T1.4, T1.17, and T1.18 cells: their maximal levels, observed after 2 minutes, were, respectively, about 160, 150, 70, and 200 times that of controls. The activity of alkaline phosphatase in MGC/T1.17 cells was higher than that in primary cultures of mouse GC cells, whereas those in MGC/T1 and T1.4 cells were comparable with that of GC cells, and that in MGC/T1.18 was lower. The three clonal lines, and especially MGC/T1.4, secreted a heat-stable, nondializable growth inhibitor(s) of endothelial cells into the culture medium. Because of their different properties, these cell lines should be useful for studies on endochondral ossification, the actions of PTH on skeletal cells, and anti-angiogenesis factors.
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PMID:Establishment from mouse growth cartilage of clonal cell lines with responsiveness to parathyroid hormone, alkaline phosphatase activity, and ability to produce an endothelial cell growth inhibitor. 255 26

Short term regulation of hepatic cholesterol ester hydrolase by reversible phosphorylation is described. Two different kinase systems seem to be involved in this regulation. The addition of ATP, cyclic AMP and Mg2+ to rat liver 104,000 X g supernatant (S104) produced a 100-140% increase in cholesterol ester hydrolase activity. This stimulation was abolished when protein kinase inhibitor was added prior to the addition of ATP, cyclic AMP and Mg2+. Cholesterol ester hydrolase activity was also stimulated when calcium ions, phosphatidylserine, and diolein were added to S104 along with ATP and Mg2+. Diolein in this reaction could be substituted by phorbol 12-myristate 13-acetate. Preincubation of S104 with alkaline phosphatase resulted in a deactivation of cholesterol ester hydrolase. The addition of increasing concentrations of Mg2+ to S104 produced increasing inhibition of cholesterol ester hydrolase activity, and this effect was blocked by NaF. It is suggested that rat liver cholesterol ester hydrolase is activated by cyclic AMP dependent protein kinase and protein kinase C. Deactivation is accomplished by dephosphorylation catalyzed by a phosphoprotein phosphatase, dependent on Mg2+.
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PMID:Activation of rat liver cholesterol ester hydrolase by cAMP-dependent protein kinase and protein kinase C. 255 47

The action of carbamoylcholine (Cchol), NaF and other agonists on the generation of inositol phosphates (IPs) was studied in dog thyroid slices prelabelled with myo-[2-3H]inositol. The stimulation by Cchol (0.1 microM-0.1 mM) of IPs accumulation through activation of a muscarinic receptor [Graff, Mockel, Laurent, Erneux & Dumont (1987) FEBS Lett. 210, 204-210] was pertussis- and cholera-toxin insensitive. Ins(1,4,5)P3, Ins(1,3,4)P3 and InsP4 were generated. NaF (5-20 mM) also increased IPs generation (Graff et al., 1987); this effect was potentiated by AlCl3 (10 microM) and unaffected by pertussis toxin. Although phorbol dibutyrate (5 microM) abolished the cholinergic stimulation of IPs generation (Graff et al., 1987), it did not affect the fluoride-induced response. Cchol and NaF did not require extracellular Ca2+ to exert their effect, and neither KCl-induced membrane depolarization nor ionophore A23187 (10 microM) had any influence on basal IPs levels, or on cholinergic stimulation. However, more stringent Ca2+ depletion with EGTA (0.1 or 1 mM) decreased basal IPs levels as well as the amplitude of the stimulation by Cchol without abolishing it. Dibutyryl cyclic AMP, forskolin, cholera toxin and prostaglandin E1 had no effect on basal IPs levels and did not decrease the response to Cchol. Iodide (4 or 40 microM) also strongly decreased the cholinergic action on IPs, this inhibition being relieved by methimazole (1 mM). Our data suggest that Cchol activates a phospholipase C hydrolysing PtdIns(4,5)P2 in the dog thyroid cell in a cyclic AMP-independent manner. This activation requires no extracellular Ca2+ and depends on a GTP-binding protein insensitive to both cholera toxin and requires no extracellular Ca2+ and depends on a GTP-binding protein insensitive to both cholera toxin and pertussis toxin. The data are consistent with a rapid metabolism of Ins(1,4,5)P3 to Ins(1,3,4)P3 via the Ins(1,4,5)P3 3-kinase pathway, followed by dephosphorylation by a 5-phosphomonoesterase. Indeed, a Ca2+-sensitive InsP3 3-kinase activity was demonstrated in tissue homogenate. Stimulation of protein kinase C and an organified form of iodine inhibit the Cchol-induced IPs generation. The negative feedback of activated protein kinase C could be exerted at the level of the receptor or of the receptor-G-protein interaction.
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PMID:Stimulation of generation of inositol phosphates by carbamoylcholine and its inhibition by phorbol esters and iodide in dog thyroid cells. 255 11

Synthesis of tryptophanase, D-serine deaminase and alkaline phosphatase in Escherichia coli C was repressed as the result of infection with the single-stranded DNA bacteriophage phi X174. However, the degree of repression differed, the more catabolite-sensitive the operon was, the more severe was the repression. For the catabolite-sensitive enzymes it was found that cyclic adenosine 3'5' monophosphate (cyclic AMP or cAMP) was unable to release or reduce the phage-induced inhibition. Experiments with amber mutants of phi X174 revealed that A, product of cistron A, was responsible for the inhibition. The cistron A product probably acted at the level of transcription. The possible role of A in the observed modulation of gene expression is discussed.
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PMID:Modulation of gene expression in Escherichia coli infected with single-stranded bacteriophage phi X174. 258 Feb 15

The existence of a metabolic disease in rheumatoid arthritis in distant zones of the active synovitis areas, remains controversial. Indeed, the variations found, by different authors, in PTH, in alkaline phosphatase and in serum and/or in the calcium urinary values, as well as in phosphate and hydroxyproline, have not clarified this problem, despite the demonstration by histomorphometry and by densitometrical methods, of a greater loss of the bone mass in rheumatoid arthritis. At the same time, metabolic changes in sexual hormones, primary or secondary, can modulate the immune response and interfere in the clinic expression of rheumatoid arthritis and also in the bone turnover. Therefore, the purpose of this study was to compare some parameters of the bone metabolism and of the hormonal condition, in women with rheumatoid arthritis, with and without corticotherapy and in an age-related control group. In Group RA (patients), we found relatively higher levels of phosphates, alkaline phosphatase and osteocalcin, just as in the nephrogenic c'AMP and the hydroxyproline/creatinine quotient. The blood levels of calcitonin, PTH, T3, T4, cortisol and estradiol did not show significant differences between the 2 groups, although they were lower in Group RA. On the contrary, the plasma levels of testosterone, of 4-androstenedione and DHEA.S were significantly reduced in patients with rheumatoid arthritis. These results are compatible with the existence of bone metabolic hyperactivity in rheumatoid arthritis, which can be related, directly or indirectly to the reduced androgens plasma levels, since these seem to play a protective role in auto-immune diseases and also on the bone metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Biomarks in secondary osteoporosis. 275 83

Recent techniques have been devised for the culture of bone cells derived from human bone explants. These cells, which are thought to represent several stages in the osteoblast lineage, respond to PTH with an increase in cyclic AMP content, and have high basal alkaline phosphatase activity which is increased on exposure to 1,25-dihydroxyvitamin D3 and decreased by PTH. Such characteristics distinguish these cells from fibroblasts. In this study, we demonstrate that human bone-derived cells also differ from fibroblasts in their growth characteristics. Bone-derived cells proliferated in basal medium supplemented with platelet-poor plasma. The rate of proliferation was enhanced by additional supplementation with platelet-derived growth factor (PDGF), and further increased when a combination of growth factors was added (PDGF, TGF-beta and EGF). In contrast, fibroblasts did not proliferate in basal medium supplemented with platelet-poor plasma and the addition of PDGF alone stimulated fibroblast proliferation to the same extent as 10% fetal bovine serum. Supplementation with other growth factors did not further enhance the response of fibroblasts to PDGF. These results emphasize the differences in proliferative responses between human bone-derived cells and human fibroblasts, and indicate that the factors responsible for osseous regeneration in vivo may differ from those factors which regulate repair of soft tissue wounds.
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PMID:Study of the growth factor requirements of human bone-derived cells: a comparison with human fibroblasts. 278 49


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