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)

We have analysed the surface antigen phenotype of a human embryonic stem (hES) cell line (H7) and the changes that occur upon differentiation induced by retinoic acid, hexamethylene bisacetamide and dimethylsulphoxide. The undifferentiated stem cells expressed Stage Specific Embryonic Antigen-3 (SSEA3), SSEA4, TRA-1-60, and TRA-1-8 but not SSEA1. In these characteristics they closely resemble human embryonal carcinoma (EC) cells derived from testicular teratocarcinomas, and are distinct from murine EC and ES cells. The undifferentiated cells also expressed the liver/bone/kidney isozyme of alkaline phosphatase detected by antibody TRA-2-54, the class 1 major histocompatability antigens, HLA-ABC, and the human Thy1 antigen. Differentiation of hES cells was induced by retinoic acid, HMBA and DMSO with the appearance of various cell types including neurons and muscle cells. The surface antigens characteristically expressed by hES cells were down-regulated following induction of differentiation and other antigens appeared, notably several ganglioside glycolipids detected by antibodies VIN-IS-56 (GD3 and GD2), VIN-2PB-22 (GD2), A2B5 (GT3) and ME311 (9-O-acetyl-GD3). Whereas the expression of HLA was slightly down-regulated upon differentiation, its expression was strongly induced by interferon-y in both the undifferentiated and the differentiated cells, although the induction in the differentiated cultures was considerably stronger than in the stem cells. In all of these features the human ES cells, and their pattern of differentiation, resembled the pluripotent human EC cell line NTERA-2 although clearly the range of cells generated by the hES cells was considerably greater.
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PMID:Surface antigens of human embryonic stem cells: changes upon differentiation in culture. 1203 29

Alkaline phosphatases are non-specific phosphomonoesterases that are distributed widely in species ranging from bacteria to man. This study has concentrated on the tissue-nonspecific alkaline phosphatase from arctic shrimps (shrimp alkaline phosphatase, SAP). Originating from a cold-active species, SAP is thermolabile and is used widely in vitro, e.g. to dephosphorylate DNA or dNTPs, since it can be inactivated by a short rise in temperature. Since alkaline phosphatases are zinc-containing enzymes, a multiwavelength anomalous dispersion (MAD) experiment was performed on the zinc K edge, which led to the determination of the structure to a resolution of 1.9 A. Anomalous data clearly showed the presence of a zinc triad in the active site, whereas alkaline phosphatases usually contain two zinc and one magnesium ion per monomer. SAP shares the core, an extended beta-sheet flanked by alpha-helices, and a metal triad with the currently known alkaline phosphatase structures (Escherichia coli structures and a human placental structure). Although SAP lacks some features specific for the mammalian enzyme, their backbones are very similar and may therefore be typical for other higher organisms. Furthermore, SAP possesses a striking feature that the other structures lack: surface potential representations show that the enzyme's net charge of -80 is distributed such that the surface is predominantly negatively charged, except for the positively charged active site. The negatively charged substrate must therefore be directed strongly towards the active site. It is generally accepted that optimization of the electrostatics is one of the characteristics related to cold-adaptation. SAP demonstrates this principle very clearly.
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PMID:The 1.9 A crystal structure of heat-labile shrimp alkaline phosphatase. 1208 16

Hypophosphatasia is a rare inborn error of metabolism characterised by defective bone mineralisation caused by a deficiency of liver-, bone- or kidney-type alkaline phosphatase due to mutations in the tissue-nonspecific alkaline phosphatase (TNSALP) gene. The clinical expression of the disease is highly variable, ranging from stillbirth with a poorly mineralised skeleton to pathologic skeletal fractures which develop in late adulthood only. This clinical heterogeneity is due to the strong allelic heterogeneity in the TNSALP gene. We found that mutation E174K is the most frequent in Caucasian patients, and that it was carried by 31% of our patients with mild hypophosphatasia. Because the mutation was found in patients of various geographic origins, we investigated whether it had a unique origin or rather multiple origins due to recurrence of de novo mutations. Three intragenic polymorphisms, S93S, 472+12delG and V505A, were genotyped in patients carrying E174K and in normal unrelated individuals. Our results show that all the E174K mutations are carried by a common ancestral haplotype, also found at low frequency in normal and hypophosphatasia chromosomes. We conclude that the TNSALP gene E174K mutation is the result of a relatively ancient ancestral mutation that occurred on a single chromosome in the north of Western Europe and spread throughout the rest of Europe and into the New World as a result of human migration.
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PMID:Evidence of a founder effect for the tissue-nonspecific alkaline phosphatase (TNSALP) gene E174K mutation in hypophosphatasia patients. 1235 39

Hypophosphatasia is a rare autosomal recessive inborn error of metabolism characterized by a defective bone mineralisation and deficiency of serum and tissue liver/bone/kidney alkaline phosphatase activity. We report the characterisation of tissue-nonspecific alkaline phosphatase (TNSALP) gene mutation in a patient affected by infantile hypophosphatasia. This boy was the first child of non affected, non related parents. At 1 month of age he presented with palsy of the left upper limb with hypotonia. Length was - 2SD. The anterior fontanel was large. There was a markedly decreased ossification of all bones. All limbs were shortened. Ultrasonographic examination of the kidneys showed nephrocalcinosis. Level of alkaline phosphatases was decreased in the child as well as in the parents. Bone density was decreased. At 2 years of age development was delayed. Weight was - 3,5 SD and OFC - 3SD. The child had craniosynostosis. Molecular studies showed 2 missense mutations, both in exon 6 of the TNSALP gene.
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PMID:Severe hypophosphatasia due to mutations in the tissue-nonspecific alkaline phosphatase (TNSALP) gene. 1241 36

A missense mutation in the gene of tissue-nonspecific alkaline phosphatase, which replaces aspartic acid at position 289 with valine [TNSALP (D289V)], was reported in a lethal hypophosphatasia patient [Taillandier, A. et al. (1999) Hum. Mut. 13, 171-172]. To define the molecular defects of TNSALP (D289V), this mutant protein in transiently transfected COS-1 cells was analyzed biochemically and morphologically. TNSALP (D289V) exhibited no alkaline phosphatase activity and mainly formed a disulfide-linked high molecular mass aggregate. Cell-surface biotinylation, digestion with phosphatidylinositol-specific phospholipase C and an immunofluorescence study showed that the mutant protein failed to appear on the cell surface and was accumulated intracellularly. In agreement with this, pulse/chase experiments demonstrated that TNSALP (D289V) remained endo-beta-N-acetyl- glucosaminidase H-sensitive throughout the chase and was eventually degraded, indicating that the mutant protein is unable to reach the medial-Golgi. Proteasome inhibitors strongly blocked the degradation of TNSALP (D289V), and furthermore the mutant protein was found to be ubiquitinated. Besides, another naturally occurring TNSALP with a Glu(218)-->Gly mutation was also found to be polyubiquitinated and degraded in the proteasome. Since the acidic amino acids at positions 218 and 289 of TNSALP are thought to be directly involved in the Ca(2+) coordination, these results suggest the critical importance of calcium binding in post-translational folding and assembly of the TNSALP molecule.
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PMID:Tissue-nonspecific alkaline phosphatase with an Asp(289)-->Val mutation fails to reach the cell surface and undergoes proteasome-mediated degradation. 1294 72

In the majority of hypophosphatasia patients, reductions in the serum levels of alkaline phosphatase activity are caused by various missense mutations in the tissue-nonspecific alkaline phosphatase (TNSALP) gene. A unique frame-shift mutation due to a deletion of T at cDNA number 1559 [TNSALP (1559delT)] has been reported only in Japanese patients with high allele frequency. In this study, we examined the molecular phenotype of TNSALP (1559delT) using in vitro translation/translocation system and COS-1 cells transiently expressing this mutant protein. We showed that the mutant protein not only has a larger molecular size than the wild type enzyme by approximately 12 kDa, reflecting an 80 amino acid-long extension at its C-terminus, but that it also lacks a glycosylphosphatidylinositol anchor. In support of this, alkaline phosphatase activity of the cells expressing TNSALP (1559delT) was localized at the juxtanucleus position, but not on the cell surface. However, only a limited amount of the newly synthesized protein was released into the medium and the rest was polyubiquitinated, followed by degradation in the proteasome. SDS/PAGE and analysis by sucrose-density-gradient analysis indicated that TNSALP (1559delT) forms a disulfide-bonded high-molecular-mass aggregate. Interestingly, the aggregate form of TNSALP (1559delT) exhibited a significant enzyme activity. When all three cysteines at positions of 506, 521 and 577 of TNSALP (1559delT) were replaced with serines, the aggregation disappeared and instead this modified mutant protein formed a noncovalently associated dimer, strongly indicating that these cysteine residues in the C-terminal region are solely responsible for aggregate formation by cross-linking the catalytically active dimers. Thus, complete absence of TNSALP on cell surfaces provides a plausible explanation for a severe lethal phenotype of a homozygote hypophosphatasia patient carrying TNSALP (1559delT).
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PMID:Novel aggregate formation of a frame-shift mutant protein of tissue-nonspecific alkaline phosphatase is ascribed to three cysteine residues in the C-terminal extension. Retarded secretion and proteasomal degradation. 1579 57

Hypophosphatasia is a rare genetic disease characterized by deficiency of tissue-nonspecific alkaline phosphatase (TNSALP) activity, excessive urinary excretion of phosphoethanolamine, poor bone mineralization and skeletal anomalies. The shortage of alkaline phosphatase (ALP) alters the process of mineralization of skeleton causing a reduced transformation of phosphoethanolamine into phosphatidylethanolamine (cerebral phospholipid) with consequent high serum and urinary levels of phosphoethanolamine, a sensitive and highly specific marker for the disease. Four clinical forms have been described based on the age of onset with different courses and prognoses. An unusual case of lethal perinatal hypophosphatasia associated with seizures observed in a newborn admitted to Neonatal Intensive Care Unit of the University of Catania is described.
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PMID:Neonatal hypophosphatasia and seizures. A case report. 1620 18

We studied the effects of phosphates on the expression of the human tissue-nonspecific alkaline phosphatase (TNSALP) gene and phosphate-regulating genes in short-term cultures of human osteoblastic osteosarcoma cell lines. When human osteosarcoma cell lines, SaOS-2, MG-63, and U(2)OS were cultured with 10 mM inorganic sodium dihydrogenphosphate, 10 mM beta-glycerophosphate, 250 microM pyridoxal phosphate, or 100 microM inorganic pyrophosphate, enzymatic activity of alkaline phosphatase began to increase at 72 h after addition of sodium dihydrogenphosphate and beta-glycerophosphate in SaOS-2 cells. Pyridoxal phosphate and pyrophosphate did not induce alkaline phosphatase activity. U(2)OS cells slightly reacted to beta-glycerophosphate, but MG-63 cells did not react on exposure to phosphates. In SaOS-2 cells, TNSALP mRNA measured by real-time RT-PCR reached a peak level at 72 h after the addition of beta-glycerophosphate. PHEX and MEPE mRNAs were also induced by beta-glycerophosphate. These results suggest that TNSALP, PHEX and MEPE were concordantly induced by beta-glycerophosphate on mineralisation.
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PMID:Effects of phosphates on the expression of tissue-nonspecific alkaline phosphatase gene and phosphate-regulating genes in short-term cultures of human osteosarcoma cell lines. 1631 17

Zinc transporters play important roles in a wide range of biochemical processes. Here we report an important function of ZnT5/ZnT6 hetero-oligomeric complexes in the secretory pathway. The activity of human tissue-nonspecific alkaline phosphatase (ALP) expressed in ZnT5(-)ZnT7(-/-) cells was significantly reduced compared with that expressed in wild-type cells as in the case of endogenous chicken tissue-nonspecific ALP activity. The inactive human tissue-nonspecific ALP in ZnT5(-)ZnT7(-/-) cells was degraded by proteasome-mediated degradation without being trafficked to the plasma membrane. ZnT5(-)ZnT7(-/-) cells showed exacerbation of the unfolded protein response as did the wild-type cells cultured under a zinc-deficient condition, revealing that both complexes play a role in homeostatic maintenance of secretory pathway function. Furthermore, we showed that expression of ZnT5 mRNA was up-regulated by the endoplasmic reticulum stress in various cell lines. The up-regulation of the hZnT5 transcript was mediated by transcription factor XBP1 through the TGACGTGG sequence in the hZnT5 promoter, and this sequence was highly conserved in the ZnT5 genes of mouse and chicken. These results suggest that zinc transport into the secretory pathway is strictly regulated for the homeostatic maintenance of secretory pathway function in vertebrate cells.
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PMID:Zinc transport complexes contribute to the homeostatic maintenance of secretory pathway function in vertebrate cells. 1663 52

Strontium is used in the treatment of osteoporosis as a ranelate compound, and in the treatment of painful scattered bone metastases as isotope. At very high doses and in certain conditions, it can lead to osteomalacia characterized by impairment of bone mineralization. The osteomalacia symptoms resemble those of hypophosphatasia, a rare inherited disorder associated with mutations in the gene encoding for tissue-nonspecific alkaline phosphatase (TNAP). Human alkaline phosphatases have four metal binding sites--two for zinc, one for magnesium, and one for calcium ion--that can be substituted by strontium. Here we present the crystal structure of strontium-substituted human placental alkaline phosphatase (PLAP), a related isozyme of TNAP, in which such replacement can have important physiological implications. The structure shows that strontium substitutes the calcium ion with concomitant modification of the metal coordination. The use of the flexible and polarizable force-field TCPEp (topological and classical polarization effects for proteins) predicts that calcium or strontium has similar interaction energies at the calcium-binding site of PLAP. Since calcium helps stabilize a large area that includes loops 210-228 and 250-297, its substitution by strontium could affect the stability of this region. Energy calculations suggest that only at high doses of strontium, comparable to those found for calcium, can strontium substitute for calcium. Since osteomalacia is observed after ingestion of high doses of strontium, alkaline phosphatase is likely to be one of the targets of strontium, and thus this enzyme might be involved in this disease.
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PMID:Structural studies of human alkaline phosphatase in complex with strontium: implication for its secondary effect in bones. 1681 19


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