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)

To study the origin of increased serum placental-like alkaline phosphatase (PLAP-like) activity in smokers, heat stable alkaline phosphatase activity was assayed from serum and bronchoalveolar lavage (BAL) fluid in 83 smoking and non-smoking patients. PLAP-like activity was increased in about 80% of the smokers, independently of the underlying lung disease. Isoenzyme activities in BAL fluid correlated (r = 0.631, p less than 0.001) with serum values. When adjusted for the albumin concentration, mean PLAP-like activity in BAL fluid was almost 1000-fold higher than that in serum, suggesting local synthesis of PLAP-like isoenzymes in the lungs. Although a direct dose-response effect was not observed, the values in serum and in BAL fluid tended to be higher in patients smoking over 10 cigarettes daily as compared to patients smoking less. In ex-smokers the results indicated that PLAP-like activity decreased to the level observed in non-smokers within 5 years after cessation of smoking. PLAP activity was L-leucine sensitive compatible with the Nagao-variant type of PLAP in almost all cases. In three patients the activity was due to the L-leucine resistant (true placental) isoenzyme.
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PMID:Increased serum placental-like alkaline phosphatase activity in smokers originates from the lungs. 367 17

We have used a mouse monoclonal antibody (H7) to placental alkaline phosphatase (PLAP, EC 3.1.3.1) in developing an immunoenzymometric assay for PLAP and PLAP-like enzymes. The antibody is bound to sheep anti-mouse IgG (Ab2) covalently coupled to tosylated shell-and-core light (1.07 g/cm3) monodisperse polymer particles. Adding the H7-Ab2-polymer particle suspension to a PLAP-containing sample gives maximal binding of the antigen within 10 min. PLAP and PLAP-like enzymes remain active and bound to the solid-phase throughout all assay manipulations, and can thus be saved for future testing. In testing the enzymes for inhibition by L-Phe, L-Phe-Gly-Gly, L-Leu, and L-homoarginine, the effect of all the inhibitors is fully reversible. The assay is highly versatile, and its sensitivity (routinely 0.05 micrograms/L) can be increased 1000-fold by adjusting the sample volume and incubation time (sample volume is irrelevant between 50 microL and 5 mL). We have measured the basal activities of PLAP in men and women and, by using enzyme inhibitors, have characterized it as corresponding to the PLAP-like phenotypes described in normal human testis.
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PMID:Highly sensitive solid-phase immunoenzymometric assay for placental and placental-like alkaline phosphatases with a monoclonal antibody and monodisperse polymer particles. 388 Jun 82

Human placental microvillous alkaline phosphatase (M-PLAP) was extracted from microvilli either by butanol extraction or subtilisin proteolysis. The data indicate that subtilisin cleavage of PLAP removes a membrane-binding domain of approximately 2000 molecular weight, leaving the catalytic site intact and the protein in solution. Sequencing studies on the N-terminal 13 amino acids of both the subtilisin-cleaved and uncleaved forms of M-PLAP indicate that the enzyme is anchored to the plasma membranes by its carboxy-terminus. The N-terminal 13 amino acids of A-PLAP were the same as those of M-PLAP. Trypsin solubilization failed to release M-PLAP from these membranes and it appears to cleave a portion of molecular weight of about 9K from the amino terminus, leaving an enzymatically active portion of PLAP associated with the membrane. On SDS gels, subtilisin-cleaved M-PLAP showed an apparent dimeric molecular size larger than that of the original uncleaved enzyme, presumably due to the generation of a less compact conformational state. On starch gels, cleaved M-PLAP showed a single zone of enzyme activity with a mobility sightly greater than that of A-PLAP, which did not require the presence of Triton X-100 to enter the gel. Variations in the apparent molecular sizes of the different allelic forms of PLAP were also observed.
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PMID:Placental alkaline phosphatase integrates via its carboxy-terminus into the microvillous membrane: its allotypes differ in conformation. 390 24

The current information on the cloning and sequencing of four alkaline phosphatase genes (PLAP, GCAP, IAP, TNAP) has been reviewed. It has provided insights into their evolutionary history and the mechanisms of catalysis and of uncompetitive inhibition. The oncodevelopmental biology of the germ cell and its excessive GCAP eutopic expression in neoplasia are noted, and there is reason to suggest that the enzyme may serve to guide migratory cells and to transport specific molecules such as fat and immunoglobulins across membranes. The hyperexpression of all four genes has been observed in various human tumors and in their cell lines, particularly cancers of the testis and ovary. The membrane APs have been investigated as targets for immunolocalization and immunotherapy.
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PMID:Biology of human alkaline phosphatases with special reference to cancer. 774 66

This article is concerned with the increase of alkaline phosphatase of a 32-year old primipara, five to six times higher than the upper basal values, during the last trimenon of pregnancy. The physiological increase of serum total alkaline phosphatase levels during pregnancy were two to three times higher than the basal values (4, 11). Hepatopathies, osteopathies, endocrinological disorders, infections as well as other medical causes were excluded by anamnesis due to close-meshed laboratory chemical and clinical controls relating to differential diagnosis. Thus, only pregnancy could be considered as a trigger mechanism. Differentiating the alkaline phosphatase by laboratory chemical means in the course of this pregnancy, an isolated increase of the alkaline phosphatase placenta isoenzyme (PLAP) was seen. Besides premature labour pains, which led to the admission of the patient to the maternity ward, around a calculated 32nd week of pregnancy, a discreet foetal growth retardation was recognised, which continued to increase constantly up to a minus discrepancy of three weeks. The delivery of a dystrophic girl took place at the beginning of the 37th week of pregnancy. Post partum alkaline phosphatase levels normalised to basal values. The correlation: the increase in PLAP and intra-uterine foetal growth-retardation was evident in the case presented and was also discussed in connection with previous observations by other authors of similar studies.
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PMID:[Excessive rise in plasma alkaline phosphatase in the last trimester of pregnancy]. 808 96

Placental alkaline phosphatase is an inducible enzyme, expressed in HeLaS3 cells, which has been shown to possess protein phosphotyrosine phosphatase activity. Since phosphotyrosine levels are known to increase in actively dividing cells we sought an inverse correlation between PLAP activity and growth rate in HeLaS3 cells. We found that PLAP inducers, Na-butyrate, dexamethasone, bromodeoxyuridine and dibutyryl cAMP caused a dose-dependent reduction in growth rate. Mimosine, an agent that blocks the cell cycle in G1, caused an increase in PLAP activity whilst the mitogen EGF caused a corresponding decrease in PLAP activity. PLAP activity may therefore be related to cell proliferation rate.
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PMID:Placental alkaline phosphatase activity is inversely related to cell growth rate in HeLaS3 cervical cancer cells. 839 40

In humans, alkaline phosphatases are encoded by one tissue-non-specific alkaline phosphatase (TNAP) gene and three tissue-specific alkaline phosphatase genes, intestinal, placental (PLAP), and germ cell-specific alkaline phosphatase (GCAP). Although the presence of alkaline phosphatases in testicular germ cell tumours (TGCTs) of adolescents and adults has been utilized for both detection and patient monitoring, it is not known in detail which isozymes are expressed. Since alkaline phosphatase is detected in carcinoma in situ (CIS), the common precursor of all TGCTs, it might provide a marker for the early diagnosis of TGCTs. Testicular cancers of germ cell and non-germ cell origin along with testicular parenchyma with and without CIS have been analysed for the expression of the different alkaline phosphatase isozymes. Antibodies to TNAP and PLAP/GCAP showed positivity in CIS, seminoma, and embryonal carcinoma. The heterogeneous staining pattern detected in frozen tissue sections was similar to the pattern found in formalin-fixed, paraffin-embedded material, indicating a biological phenomenon and not a handling artefact. Since PLAP and GCAP cannot be distinguished using immunohistochemistry, the expression of these isozymes was studied at the molecular level using a reverse transcriptase-polymerase chain reaction (RT-PCR) approach, in combination with a primer extension assay. The results show that CIS and seminoma predominantly express GCAP, while in embryonal carcinoma the expression of GCAP versus PLAP varies. Due to the presence of alkaline phosphatase transcripts in normal testicular parenchyma, an RT-PCR-based analysis of alkaline phosphatase is not informative for the early detection of TGCTs in biopsy samples.
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PMID:Heterogeneity in alkaline phosphatase isozyme expression in human testicular germ cell tumours: An enzyme-/immunohistochemical and molecular analysis. 1054 81

NE-4C, one-cell derived neuroectodermal stem cells expressing a reporter gene--green fluorescent protein (GFP) or heat-resistant alkaline phosphatase (PLAP)--or prelabeled with bromodeoxyuridine (BrdU) were implanted into the forebrain of adult, new-born and fetal mice and into the mid- and forebrain vesicles of early chick embryos. The fate of implanted cells in the mouse and chick hosts was followed up to 6 and 2 weeks, respectively. Neural differentiation was monitored by detecting the expression of neuron-specific markers and GFAP. NE-4C cells integrated into the early embryonic brain tissue and developed into morphologically differentiated neurons. The same cells produced expanding tumor-like aggregates in the newborn forebrain and were expelled from the adult forebrain parenchyma. In the adult brain, long-term survival and integration of stem cells were revealed only in neurogenic zones. The data suggest that noncommitted, proliferating neuroectodermal progenitors can integrate into the brain tissue at time and site of tissue genesis.
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PMID:Fate of cloned embryonic neuroectodermal cells implanted into the adult, newborn and embryonic forebrain. 1524 25

In mammalian alkaline phosphatase (AP) dimers, the N-terminus of one monomer embraces the other, stretching toward its active site. We have analyzed the role of the N-terminus and its microenvironment in determining the enzyme stability and catalysis using human placental (PLAP) and tissue-nonspecific AP (TNAP) as paradigms. Deletion of nine amino acid (aa) residues in PLAP reduced its AP activity and heat stability, while deletion of 25 aa resulted in an inactive enzyme. In turn, deletion of five and nine N-terminal aa in TNAP reduced and abolished AP activity, respectively. The N-terminal aa deletions in both isozymes affected the rate of substrate catalysis (k(cat)), with an only minor effect on the Michaelis constant (K(m)) explained by decelerated intramolecular transition rates in the active site. Arg370 in PLAP, and the corresponding Arg374 in TNAP, critically control the structure and function of the enzymes, but the Glu6-Arg370 bond predicted by the PLAP crystal structure appeared to be irrelevant with respect to PLAP stability or catalysis. Structural disruption was also noted in [R374A]TNAP, [Delta5]TNAP, [Delta9]TNAP, and [Delta25]TNAP using a panel of 19 anti-TNAP antibodies illustrating the structural role of the N-terminus. Our data reveal that the N-terminal alpha-helical folding is more crucial for the structural stability of the second monomer in TNAP than in PLAP. The correct folding of the N-terminus and of interacting loops in its immediate environment is essential for overall structural integrity and for execution of intramolecular transitions during enzyme catalysis. These findings provide a mechanistic interpretation for loss-of-function mutations of N-terminal TNAP residues in cases of hypophosphatasia.
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PMID:Mammalian alkaline phosphatase catalysis requires active site structure stabilization via the N-terminal amino acid microenvironment. 1689 77

The tissue-nonspecific alkaline phosphatase (TNAP) isozyme is centrally involved in the control of normal skeletal mineralization and pathophysiological abnormalities that lead to disease states such as hypophosphatasia, osteoarthritis, ankylosis and vascular calcification. TNAP acts in concert with the nucleoside triphosphate pyrophosphohydrolase-1 (NPP1) and the Ankylosis protein to regulate the extracellular concentrations of inorganic pyrophosphate (PP(i)), a potent inhibitor of mineralization. In this review we describe the serial development of two miniaturized high-throughput screens (HTS) for TNAP inhibitors that differ in both signal generation and detection formats, but more critically in the concentrations of a terminal alcohol acceptor used. These assay improvements allowed the rescue of the initially unsuccessful screening campaign against a large small molecule chemical library, but moreover enabled the discovery of several unique classes of molecules with distinct mechanisms of action and selectivity against the related placental (PLAP) and intestinal (IAP) alkaline phosphatase isozymes. This illustrates the underappreciated impact of the underlying fundamental assay configuration on screening success, beyond mere signal generation and detection formats.
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PMID:Assay format as a critical success factor for identification of novel inhibitor chemotypes of tissue-nonspecific alkaline phosphatase from high-throughput screening. 2065 62


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