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PubMed1979

Human cell lines expressing intestinal alkaline phosphatase.

At least three loci determine human alkaline phosphatases [orthophosphoric-monoester phosphohydrolase (alkaline optimum), EC 3.1.3.1]: one coding for the placental form of the enzyme, at least one coding for the intestinal forms, and at least one for the liver, bone, and kidney forms. The alkaline phosphatase in cell line D98/AH-2 has been characterized by inhibition, thermostability, and electrophoretic studies. It is intestinal in type and resembles the fetal intestinal form somewhat more closely than the adult intestinal form. Intestinal alkaline phosphatase was found in the related cell lines Detroit 98, D98/S, and D98/AH-R. No placental alkaline phosphatase could be detected in any of these cell lines. This series of cell lines are believed, on the basis of earlier investigations, to be HeLa in origin but other HeLa cell lines show placental alkaline phosphatase. Loss of expression of the placental alkaline phosphatase locus probably occurred prior to the separation of Detroit-98 from the lineage leading to other HeLa cell lines and this has persisted in the Detroit-98 derivatives D98/AH-2, D98/S, and D98/AH-R. Another possibility is that placental alkaline phosphatase expression only appeared in the HeLa lineage subsequent to the separation of Detroit-98.

Alkaline Phosphatase↗
PubMed1977

Synthesis and processing of an Escherichia coli alkaline phosphatase precursor in vitro.

Alkaline phosphatase [orthophosphoric-monoester phosphohydrolase (alkaline optimum), EC 3.1.3.1] of E. coli was synthesized in a cell-free system, and the size of the direct translation product was analyzed. The product has a higher molecular weight than the mature alkaline phosphatase found in the periplasm. The direct translation product can be processed to the mature size by an E. coli membrane fraction; the processing activity copurifies with the outer-membrane fraction. The presumed precursor can dimerize to form active enzyme without being processed, and the resultant enzyme appears to be more hydrophobic than the mature enzyme. These findings are discussed in connection with the "signal hypothesis" proposed for the excretion of proteins across membranes.

Alkaline Phosphatase↗
PubMed1988

Micro-scale two-dimensional electrophoresis of alkaline phosphatase from serum.

Isoenzymes of alkaline phosphatase (EC 3.1.3.1) were separated by micro-scale two-dimensional electrophoresis, with isoelectric focusing in capillary gels in the first dimension and polyacrylamide gradient-gel electrophoresis in the second. The isoenzymes detected were identified by several treatments--e.g., incubation with sialidase, papain, Triton X-100, and wheat-germ agglutinin--and by comparison with alkaline phosphatase from liver microsomes. Liver and bone isoforms in normal sera showed overlapping isoelectric points but differed in molecular mass, estimated as 172 and 185 kDa, respectively. Sera of patients with liver disease showed several additional groups of alkaline phosphatase isoforms, two of which were found to consist of multi-molecular complexes. Others probably correspond to incompletely glycated enzyme proteins. A further isoform with a mass of about 250 kDa does not seem to correspond to any known isoform of alkaline phosphatase in serum. With this technique, we demonstrated intra- and interindividual variations of the placental alkaline phosphatase isoenzyme in pregnancy sera.

Adult↗
PubMed1987

Characterization of a human osteoblastic osteosarcoma cell line (SAOS-2) with high bone alkaline phosphatase activity.

We characterized the alkaline phosphatase activity of the human osteogenic sarcoma cell line, SAOS-2, and studied the regulation of this enzyme and 3',5'-cyclic adenosine monophosphate levels by 1,25-dihydroxyvitamin D3 and triamcinolone acetonide. We report that the basal alkaline phosphatase activity of SAOS-2 cells was 100-1000 times greater than that of other established human osteogenic sarcoma cell lines. The enzymatic activity was thermolabile, could be inhibited by levamisole and L-homoarginine, but not by L-phenylalanine, and was immunoprecipitable with anti-bone/liver/kidney, but not with anti-placental antibody, confirming that it is the tissue-unspecific or bone/liver/kidney isoenzyme. However, in contrast to other established human osteosarcoma cell lines (TE-85, SAOS-1), in which alkaline phosphatase activity is stimulated several-fold by the steroid hormones 1,25-dihydroxyvitamin D3 and hydrocortisone, the alkaline phosphatase activity of SAOS-2 cells was not affected by 1,25-dihydroxyvitamin D3 treatment despite the presence of classical receptors for this hormone. Furthermore, administration of the potent glucocorticoid analogue, triamcinolone acetonide, induced only a modest increase in activity. The SAOS-2 cell line expressed low basal cAMP levels (28 pmol/10(6) cells) which could be increased 25-40 times by pretreatment with parathyroid hormone. However, unlike other osteoblastic models, in which PTH-induced cAMP stimulation is modulated by 1,25-dihydroxyvitamin D3 and glucocorticoids, neither of these hormones had an effect on the PTH-stimulated cAMP levels in SAOS-2 cells. We conclude that the SAOS-2 cell line is an osteoblastic cell model which expresses high levels of tissue-unspecific alkaline phosphatase activity and exhibits limited responsiveness to two steroid hormones.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1986

Multiple form of L-phenylalanine sensitive alkaline phosphatase in rat fecal extracts.

Alkaline phosphatase activity was detected in fecal extracts of male rats. 58% of the total enzyme activity was inhibited by 30 mM L-phenylalanine, which is an inhibitor specific for intestinal alkaline phosphatase. L-Phenylalanine sensitive alkaline phosphatase in the fecal extracts revealed multiple peaks on DEAE-Sephadex A-25 ion exchange column with a linear gradient of NaCl. It is discussed that a part of the fecal alkaline phosphatase might be a set of catabolites of the intestinal enzyme.

Alkaline Phosphatase↗
PubMed1983

Relationship of plasma tartrate resistant acid phosphatase to the bone isoenzyme of serum alkaline phosphatase in hyperparathyroidism.

In 46 patients with primary hyperparathyroidism, in 21 non-dialysed patients with advanced renal failure, and in 52 patients on hemodialysis, a significant positive correlation was found between bone isoenzyme of serum alkaline phosphatase and plasma tartrate resistant acid phosphatase. In primary hyperparathyroidism, a significant positive correlation was found between the radiological degree of osteodystrophy and the biochemical parameters of bone remodelling. After removal of the parathyroid adenoma, only the tartrate-resistant acid phosphatase decreased to normal limits. Plasma tartrate resistant acid phosphatase was most significantly influenced by serum immunoreactive parathyroid hormone levels. In chronic renal failure, bone isoenzyme of serum alkaline phosphatase was most significantly influenced by serum immunoreactive parathyroid hormone levels, by hypocalcemia and by duration of hemodialysis. The results confirm that in hyperparathyroidism the extent of the whole-body rates of bone resorption and formation are approximately equal. The biochemical parameters can be used for serial assessment of the course of the disease but are not specific for diagnosis.

Acid Phosphatase↗
PubMed1981

Evidence for histidyl residues at the Zn2+ binding sites of monomeric and dimeric forms of alkaline phosphatase.

Chemical modification of Escherichia coli alkaline phosphatase using the group-specific reagent, ethoxyformic anhydride, has demonstrated that 3 histidyl residues/subunit are modified with a concomitant loss of enzyme activity. Reaction with [14C]ethoxyformic anhydride indicates that only three ethoxyformyl groups are incorporated per subunit, confirming that no other amino acid residues are modified under these conditions. Zinc ions protect alkaline phosphatase from inactivation as well as from histidine modification, thus implicating all 3 histidyl residues in Zn2+ binding. The ethoxyformylation reaction was also used to characterize Zn2+ binding sites in immobilized dimeric and monomeric alkaline phosphatase derivatives. The immobilized dimeric alkaline phosphatase was inactivated with ethoxyformic anhydride at a rate similar to that of the soluble enzyme, demonstrating that immobilization did not significantly alter the chemical environment of the Zn2+ binding site. The catalytically inactive, immobilized monomer of alkaline phosphatase was modified more rapidly with ethoxyformic anhydride, demonstrated by the loss of its ability to form functionally active enzyme upon titration with nascent soluble subunits. Moreover, Zn2+ protects the immobilized subunit alkaline phosphatase against this modification, indicating that the isolated subunits of alkaline phosphatase bind Zn2+. These results are consistent with a model for renaturation of the dimeric enzyme in which individual subunits refold and bind Zn2+ before which individual subunits refold and bind Zn2+ before establishing subunit interactions to regain catalytic activity.

Alkaline Phosphatase↗
PubMed1980

Synthesis of first trimester placental alkaline phosphatase in cultured human term placental cells.

Alkaline phosphatase activity in human placental cells transformed by a tsA mutant of simian virus 40 (SV40) can be greatly induced by growing these cells at 40 degrees C, the temperature at which the tsA transformants regain their nontransformed phenotype. The induction of alkaline phosphatase in these cells requires the synthesis of both RNA and protein. The induced alkaline phosphatase from a SV40 tsA30 mutant-transformed term placental cell line (TPA30-1) was purified, characterized, and compared with alkaline phosphatase from term placenta and first trimester placenta. The form of alkaline phosphatase found in TPA30-1 cells differs from the phosphatase of term placenta in physiochemical and immunological properties. The TPA30-1 phosphatase is, however, indistinguishable from the alkaline phosphatase of human first trimester placenta by several criteria, including electrophoretic mobility, apparent molecular weight (Mr = 165,000), size of monomeric subunit (Mr = 77,000), heat lability, and sensitivity to inhibition by amino acids and EDTA. In addition, alkaline phosphatase from both TPA30-1 cells and first trimester placenta can be inactivated by antiserum to liver alkaline phosphatase but not by antiserum to term placental alkaline phosphatase. The induction of first trimester phosphatase in cells derived from term placenta provides a system for the study of alkaline phosphatase gene regulation in human placenta.

Alkaline Phosphatase↗