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PubMed1988

Biosynthesis of placental alkaline phosphatase and its post-translational modification by glycophospholipid for membrane-anchoring.

The biosynthesis and post-translational modification of placental alkaline phosphatase were studied in human choriocarcinoma cells, JEG-3. Pulse-chase experiments with [35S]methionine demonstrated that placental alkaline phosphatase was synthesized as a major precursor form with Mr 63,000, which was then converted to a mature form with Mr 66,000, by processing of its N-linked oligosaccharides from the high-mannose type to the complex type. In addition, the two forms of the protein were found to be modified by a glycophospholipid, components of which were characterized by metabolic incorporation into placental alkaline phosphatase of 3H-labeled compounds such as myo-inositol, palmitic acid, stearic acid, mannose, glucosamine, and ethanolamine. When placental alkaline phosphatase labeled with these compounds was treated with phosphatidylinositol-specific phospholipase C or papain, the phospholipase C removed only the 3H-labeled fatty acids, whereas papain, that is known to cleave the C-terminal region, released all the radioactive glycolipid components including [3H]ethanolamine. More detailed analysis with shorter pulse-chase experiments demonstrated that placental alkaline phosphatase was primarily synthesized as a form with Mr 64,500 which was not yet labeled with [3H]palmitic acid. This form was converted by papain digestion to the above-mentioned major precursor with Mr 63,000. Taken together, these results suggest that placental alkaline phosphatase is initially synthesized as the precursor with Mr 64,500, which is immediately converted to the intermediate form with Mr 63,000 by simultaneously occurring proteolysis of the C terminus and replacement by the glycophospholipid, and finally to the mature form with Mr 66,000 by terminal glycosylation of its N-linked oligosaccharides. The glycophospholipid thus attached is considered to function as the membrane-anchoring domain of placental alkaline phosphatase.

Alkaline Phosphatase↗
PubMed1997

Stage-specific expression patterns of alkaline phosphatase during development of the first arch skeleton in inbred C57BL/6 mouse embryos.

Timing and pattern of expression of alkaline phosphatase was examined during early differentiation of the 1st arch skeleton in inbred C57BL/6 mice. Embryos were recovered between 10 and 18 d of gestation and staged using a detailed staging table of craniofacial development prior to histochemical examination. Expression of alkaline phosphatase is initiated at stage 20.2 in the plasma membrane of mesenchymal cells in the distal region of the first arch. Expression is strongest in osteoid (unmineralised bone matrix) and presumptive periosteum at stage 21.32. Mineralisation begins at stage E23. Expression is present in the mineralised bone matrix. Secondary cartilages form in the condylar and angular processes by stage M24. The cartilaginous cells and surrounding cells in the processes are all alkaline phosphatase-positive and surrounded by the common periosteum, suggesting that progenitor cells of the processes, dentary ramus and secondary cartilages all originate from a common pool. Nonhypertrophied chondrocytes of Meckel's cartilage express alkaline phosphatase at stage M23. Expression in these chondrocytes is preceded by the expression in their adjacent perichondrium. This is true of chondrocytes in all other cranial cartilages examined. 3-D reconstruction of expression in Meckel's cartilage also revealed that the chondrocytes of Meckel's cartilage which express alkaline phosphatase and the matrix of which undergoes mineralisation are those surrounded by the alkaline phosphatase-positive dentary ramus. By stage 25, coincident with mineralisation in the distal section of Meckel's cartilage, most chondrocytes are strongly positive. The perichondria of malleus and incus cartilages express alkaline phosphatase at stage M24. Nonhypertrophied chondrocytes along these perichondria also express alkaline phosphatase. Superficial and deep cells in the dental laminae of incisor and 1st molar teeth become alkaline phosphatase-positive at the bud stage, stages 21.16 and 21.32, respectively. Dental papillae are negative until stage M24 when alkaline phosphatase expression begins in the dental papillae and follicles of the incisor teeth and the dental follicles of the 1st molar teeth. The dental papillae of the 1st molar teeth express alkaline phosphatase at stage 25. Expression in the dental papillae and follicles appears to coincide with cellular differentiation of follicle from papilla. The presumptive squamosal, ectotympanic and gonial membrane bones, lingual oral epithelial cells connected to the dental laminae of the incisor teeth, hair follicle papillae and sheath and surrounding dermis all express alkaline phosphatase in a stage-specific manner.

Alkaline Phosphatase↗
PubMed1979

Demonstration of placental alkaline phosphatase in human breast cancer.

The screening of a series of 11 metastatic breast tumors for the presence of the placental isoenzyme of alkaline phosphatase (EC3.1.3.1) by RIA revealed one strong producer. The alkaline phosphatase of this tumor was characterized with respect to its immunochemical cross-reactivity, inhibition by L-phenylalanine and levamisole, subunit molecular weight (Mr) and isoelectric point (pl) in two-dimensional electrophoresis, and one-dimensional peptide map. In all parameters of the characterization, the tumor alkaline phosphatase, except for subunit molecular weight which was slightly lower (60,000 versus 64,000 for the placental isoenzyme). No strong placental alkaline phosphatase producers were found among 16 primary tumors examined by RIA. The screening of patients' sera for the placental alkaline phosphatase using RIA indicated elevated levels over post-menopausal controls in 20% of the metastatic patients. Only 3% of the primary patients had elevated serum levels. These results suggest that the placental isoenzyme of alkaline phosphatase may be a useful tumor marker for recurrent breast cancer.

Alkaline Phosphatase↗
PubMedDate not supplied

[Characterization of clofibrate-stimulated alkaline phosphatase in rat liver].

Hypolipidemic agent clofibrate induced the alkaline phosphatase activity in rat liver but did not affect this activity in kidney, brain, heart and intestine. In liver cells the clofibrate induced alkaline phosphatase was localized in plasma membrane and cytosol and was similar to the enzyme found in normal hepatocytes by its main properties (pH optimum, inactivation temperature, substrate specificity, Km, effect of inhibitors and inducers). The putative mechanism of the alkaline phosphatase induction in liver tissue by means of clofibrate is discussed.

Alkaline Phosphatase↗
PubMed1990

Further characterization of a heat-stable alkaline phosphatase with low sensitivity to L-phenylalanine.

A heat-stable alkaline phosphatase, hitherto found in two families with inherited hyperphosphatasemia, was further characterized. The enzyme was similar to serum placental alkaline phosphatase from pregnant women concerning its apparent affinity constant (Km) for 4-nitrophenyl phosphate and its reactivity with H7 monoclonal anti-placental alkaline phosphatase (PLAP) antibodies, but different in the following respects: it exhibited greater heat stability, a higher pH optimum, lower sensitivity to inhibition by L-phenylalanine, and no reactivity with C2 monoclonal anti-PLAP antibodies. The low sensitivity to L-phenylalanine suggests that the enzyme might correspond to a rare phenotype of placental alkaline phosphatase found in human term placenta.

Alkaline Phosphatase↗
PubMed1980

Histochemical mapping of alkaline phosphatase in the digestive system of a few teleost fishes.

The alkaline phosphatase activity is mapped in all the parts of the digestive system of Colisa fasciatus, Macrognathus aculeatus, Notopterus notopterus and Nandus nandus. In the posterior region of the alimentary canal of all the 4 fishes the activity is poorer as compared to other parts. In Colisa fasciatus and Macrognathus aculeatus, the activity at the distal end of pyloric caeca is poorer as compared to the proximal part. In Notopterus notopterus and Nandus nandus however, it is practically of the same intensity at both the parts. Mucosal and submucosal layers have been found to have intense alkaline phosphatase activity as compared to muscularis and serosal layers. Except Nandus nandus, gastric glands of all the remaining fishes show partial activity of this enzyme. However, gastric epithelium of all the four fishes shows good activity. Hepatic cells are rich in alkaline phosphatase activity. The cytoplasm of the hepatic cells and pancreatic acinar cells have intense reaction. Presence of alkaline phosphatase is in relation with the secretory and absorption activity of tissue or cells.

Alkaline Phosphatase↗
PubMed1978

Some pitfalls in the quality control of alkaline phosphatase activity.

A study of the pH optimum of alkaline phosphatase activity in calibration and control serum preparations reveals a wide variation in pH optima. It is shown that as small an error of +/- 0.05 pH units in preparation of the buffered substrate results in an error in the order of +/- 5% in the response between the calibrating serum and patient specimens. It is recommended that a calibration serum should closely parallel the pH optimum of alkaline phosphatase in human sera and that a quality control serum containing alkaline phosphatase of alternative source to that present in the calibration serum be included with patient samples as a sensitive means of monitoring pH changes in the buffered substrate.

Alkaline Phosphatase↗
PubMed1976

Transient bile duct obstruction. Response of serum bilirubin and alkaline phosphatase levels in the rat.

The immediate evolution of changes in serum bilirubin and alkaline phosphatase levels during and after brief temporary occlusion (12 hours or less) of the main bile duct was studied in the rat. Transient obstruction of the main bile duct of more than one hour was characterized by a simultaneous increase in serum levels of both bilirubin and alkaline phosphatase. The time required for return to normal values was less for bilirubin than the duration of a brief obstruction and was more prolonged for alkaline phosphatase than the duration of obstruction. In obstruction of four or more hours, it was rare to find an isolated elevation of serum bilirubin; this occurred when the control value for alkaline phosphatase levels was low and their relative increase was obscured. Thus, an isolated increase in the serum bilirubin level is infrequently compatible with obstruction of the bile duct, even when transient and of brief duration. Conversely, isolated elevation of serum alkaline phosphatase levels in an acute abdominal syndrome may indicate relieved biliary obstruction.

Alkaline Phosphatase↗
PubMed1985

Ultracytochemical demonstration of alkaline phosphatase activity in astrocytes and subependymal cells in the rat brain.

Ultrastructural localization of alkaline phosphatase activity was studied in astrocytes of the cerebral cortex and corpus callosum, and in the ependymal and subependymal cells of the lateral ventricle of normal rat brain by means of electron microscopic histochemistry employing the lead citrate method. Astrocytes exhibited alkaline phosphatase activity on the plasma membrane of the endfeet facing the vascular basement membrane and at the gap junctions, but not on other parts of the plasma membrane or in the cytoplasm. Immature astrocytes containing small bundles of filaments, a few glycogen granules and other cell organelles, exhibited alkaline phosphatase activity on the inner and outer nuclear membranes, the outer mitochondrial membrane and on portions of the plasma membrane. Thus, it was concluded that the distribution of alkaline phosphatase in astrocytes shifts from the cytoplasm and plasma membrane to the endfeet and gap junctions with cell maturation. Alkaline phosphatase activity was detected on the plasma membrane of the subependymal cells and surrounding processes, but not on the ependymal cells.

Alkaline Phosphatase↗
PubMed1976

[Distribution pattern of isoenzymes of alkaline phosphatase in patients with various forms of hepatitis (author's transl)].

The isoenzymes of alkaline phosphatase were measured on admission to hospital, and then weekly over a 2 to 3 month period, in 40 patients presenting with uncomplicated acute hepatitis, 12 patients with cholestatic hepatitis, and 10 patients with histologically confirmed chronic persistent hepatitis. In acute uncomplicated hepatitis the increase in total alkaline phosphatase is not due to a cholestatic reaction of the damaged liver, but reflects the impaired catabolic capacity of the liver cells to degrade alkaline phosphatases from intestine and bone, as well as that of hepato-biliary origin. The isoenzyme distribution pattern is the same as found in normal healthy subjects. The increase in total alkaline phosphatase in patients with cholestatic hepatitis results from this impaired catabolic capacity for degradation of all isoenzymes, together with an increase in cholestatic reflux of hepato-biliary enzymes. In patients with chronic persistent hepatitis the raised total alkaline phosphatase activity at each point during the illness is due to this catabolic impairment of degradation of all isoenzymes. A cholestasis is not seen. The isoenzyme distribution pattern remains normal; only the enzyme activity due to the intestinal fraction, when compared with the acute hepatitis, is slightly, but significantly, raised.

Acute Disease↗
PubMed1978

Ultrastructural localization of alkaline phosphatase in the hypertrophic chondrocyte of the frog.

The ultrastructural localization of alkaline phosphatase was studied in the hypertrophic chondrocyte of the frog (Rana temporaria) by incubating sections of glutaraldehyde fixed tissue in a medium containing sodium beta glycerophosphate and calcium chloride. Control specimens were incubated in substrate free medium. Alkaline phosphatase (orthophosphoric monoester phosphohydrolase) is a high molecular weight glycoprotein that hydrolyses phosphorylated metabolites much as acid phosphatase does except that its action is optimal at an alkaline pH. The results of this investigation showed that alkaline phosphatase activity was present within the cytoplasm and around the plasma membrane of frog hypertrophic chondrocytes. Although only a small proportion of frog hypertrophic chondrocytes demonstrated enzyme activity, there was evidence that this was concentrated within Golgi lamellae and vesicles leaving other organelles unreactive. The finding of alkaline phosphatase activity within Golgi lamellae of hypertrophic chondrocytes is regarded as unusual although postitive reactions within chondrocyte lysosomes have previously been reported (Doty and Schofield, 1976).

Alkaline Phosphatase↗
PubMed1998

Normal alkaline phosphatase levels in patients with bone metastases due to renal cell carcinoma.

OBJECTIVES: To determine the correlation between alkaline phosphatase levels and bone metastases in renal cell carcinoma. METHODS: The records of two cohorts, including 539 and 184 patients, with metastatic renal cell carcinoma were reviewed. In both groups, metastases were shown on magnetic resonance imaging (MRI), computed tomography (CT), or bone scan. In addition, the second cohort included data concerning pain on presentation. None of the patients in either cohort had any systemic therapy (chemotherapy or immunotherapy); many patients had undergone radical nephrectomy as the primary treatment of the cancer. All radiographic and laboratory information was obtained within a 6-week enrollment period. Normal alkaline phosphatase levels were referenced according to age and sex, resulting in an upper limit of normal of 111 to 141 U/L. RESULTS: In the first cohort bone metastases were documented by MRI, CT, and/or bone scans in 164 patients. Alkaline phosphatase levels were less than or equal to 141 U/L in 118 patients (72%) and less than or equal to 111 U/L in 87 patients (53%). There were 123 patients with bone metastases who had previously undergone a nephrectomy for presumed local disease. Alkaline phosphatase levels were less than or equal to 141 U/L in 91 patients (74%) and less than or equal to 111 U/L in 70 patients (57%). In the second cohort 22 of 37 patients (59%) had little to no pain on presentation, and 19 (86%) of that group had normal alkaline phosphatase levels. CONCLUSIONS: Alkaline phosphatase is an insensitive indicator of bone metastases.

Adult↗
PubMed1979

Experimentally induced autoantibody to heat-stable alkaline phosphatase in the baboon.

Experimental evidence has been collected which signifies that autoantibody has been induced against lung heat-stable alkaline phosphatase which represented 60% of the total alkaline phosphatase of that tissue. Immunization of a male baboon with highly purified human placental alkaline phosphatase (heat-stable and cross-reactive with the baboon heat-stable enzyme) resulted in production of a precipitating factor in the immune serum which reacted with the heat-stable enzyme of both the human and baboon but not the heat-labile form of alkaline phosphatase of either species. This precipitating factor is a baboon autoantibody because 1) it had a gamma mobility on immunoelectrophoresis and retarded the electrophoretic mobility of the heat-stable enzyme from both normal and immunized baboons; 2) its titer increased as more booster injections were administered; 3) it formed a well-defined precipitin rocket with the baboon heat-stable enzyme in the Lurell's antigen-antibody crossed electrophoresis; 4) in immunodiffusion it formed a discrete precipitin line with the baboon heat-stable enzyme, which fused partially with the precipitin line of human placental alkaline phosphatase (immunogen).

Alkaline Phosphatase↗
PubMed1978

Alkaline phosphatase in developing teeth and bone of man and macaque monkey.

The activity of nonspecific alkaline phosphatase (E.C. 3.1.3.1) in developing teeth and bone of human fetuses and young macaque monkeys has been studied by means of histochemistry. The incubations for alkaline phosphatase were performed at pH 8.2 using naphthol-AS-MX-phosphate as substrate and Fast Blue RR salt or Fast Red Violet LB salt as couplers. By means of pretreatment with heat (56 degrees C), or addition of sodium metavanadate, ortho- or pyrophosphate, two alkaline phosphatases were demonstrated in the developing teeth. Prior to hard tissue formation all alkaline phosphatase activity was inhibited by the addition of vanadate, phosphate, or by pretreatment with heat. Pretreatment with heat or addition of vanadate or phosphate also inhibited alkaline phosphatase activity in the odontoblasts and in the pulpal connective tissue, whereas the activity in the subodontoblastic cell layer, stratum intermedium, outer enamel epithelium, and the the outer cells of the reduced enamel epithelium were much less affected. A week resistant activity was also noted in odontoblasts and pulpal connective tissue.

Alkaline Phosphatase↗
PubMed1975

The diagnostic value of certain alkaline phosphatase isoenzyme patterns in human serum, fractions obtained by polyacrylamide disc electrophoresis.

Over 2500 pathological sera were analysed to determine alkaline phosphatase (EC 3.1.3.1) isoenzyme levels. 3% of these sera showed two or more narrow isoenzyme bands with a lower electrophoretic mobility on polyacrylamide than that of the intestine type of alkaline phosphatase and higher than that of the bile type of alkaline phosphatase (the extra-bands group). This latter group showed significantly more intestine-tupe alkaline phosphatase than a control group of 240 sera lacking extra serum bands. Significantly more of the individuals in the extra-bands group belonged to blood group O or B than did individuals of the control group. This relationship with blood groups suggests that the presence of the extra bands is genetically determined. It is concluded that the presence of these extra bands is not a specific indication for a particular disease or malignant process. The serum of seven patients showed an unusually strong alkaline phosphatase band with a relative mobility amounting to about one-third of that of the liver-type band (2nd fraction group). Specificity for a particular disease could not be established in this group either. In four patients the serum showed an alkaline phosphatase band with an electrophoretic mobility greater than that of the liver-tupe band (6th fraction group). All of these patients had liver metastases of a primary adenocarcinoma localized in the pancreas or stomach. After the demonstration of this fraction in ther serum, the course became progessively worse.

ABO Blood-Group System↗
PubMed1986

Affinity electrophoresis of human serum alkaline phosphatase isoenzymes in agarose gel containing lectin.

Separation of alkaline phosphatase isoenzymes using affinity electrophoresis in agarose gel containing lectin is described. The bone and biliary isoenzymes precipitate during electrophoresis and are clearly separated from the liver isoenzyme. The liver, intestinal and placental alkaline phosphatases are essentially not affected by the lectin. The migration distances of the precipitating bone and biliary fractions vary with their alkaline phosphatase activity. The bone isoenzyme is more heterogeneous than the biliary isoenzyme with respect to interaction with lectin forming both insoluble and soluble complexes. Affinity electrophoresis in agarose gel containing lectin can be used for quantitation by densitometry of liver and bone isoenzymes in sera containing only these two fractions but must be combined with conventional electrophoresis, preferably in agar gel, if biliary, intestinal, or placental isoenzymes are also present.

Alkaline Phosphatase↗
PubMed1985

Glucocorticoid regulation of alkaline phosphatase in the osteoblastic osteosarcoma cell line ROS 17/2.8.

Dexamethasone increased alkaline phosphatase levels up to 7-fold in the osteoblast-like rat osteosarcoma cell line ROS 17/2.8. This effect was associated with reduced cell growth and took place over several days in culture. The increase in enzyme activity was dose dependent, (half-maximum near 1 nM, with a hormone specificity suggesting glucocorticoid receptor mediation). Dexamethasone also increased enzyme activity in ROS 2/3 cells, but not in two nonosteoblastic osteosarcoma cell lines, indicating that among these cell lines, the effect is specific for osteoblast-like cells. Moreover, enzyme activity in both control and dexamethasone-treated cells correlated directly with levels of radioimmunoassayable bone-type isoenzyme. Increases in alkaline phosphatase activity in response to dexamethasone were detectable after about 5 h and were inhibited by both actinomycin D and cycloheximide. Thus glucocorticoids appear to increase de novo enzyme synthesis in ROS 17/2.8 cells. Finally, the cAMP-elevating agents PTH, isoproterenol, and 8-bromo-cAMP, which were previously shown to reduce alkaline phosphatase activity in osteoblast-like cells, antagonized the effects of dexamethasone. Moreover, in the presence of dexamethasone, lower concentrations of these agents were required for inhibitory effects on alkaline phosphatase.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1984

Size and stability to sodium dodecyl sulfate of alkaline phosphatases from their three established human genes.

Subunit molecular weights of human alkaline phosphatases (orthophosphoric-monoester phosphohydrolases (alkaline optimum), EC 3.1.3.1) determined by polyacrylamide gel electrophoresis in sodium dodecyl sulfate (SDS) were dependent upon acrylamide concentration, a reflection of their glycoprotein nature. Molecular weights at a concentration of 7% (w/w) or greater were 68300, 80800 and 79400 for the enzymes from placenta, liver and mucosa of small intestine, respectively. All enzymes were dimers, the respective native Mr values determined by gradient gel electrophoresis being 138000, 186000 and 180000. None of the molecular weights was altered by desialylation. Stability of the catalytic activity of the purified enzymes to SDS varied and was very dependent on pH. SDS at 1% (w/v) rapidly denatured both native and desialylated alkaline phosphatase from placenta at pH 7.5 but had little effect on these at pH 10.3. Compared with placenta, the native enzyme from liver had greater stability at pH 7.5 and both native and desialylated forms had lower stability at pH 10.3. The enzyme from intestinal mucosa was sharply different from the other two isoenzymes: SDS had little effect at pH 7.5 but very rapidly denatured the enzyme at pH 10.3. The size of alkaline phosphatases and their stability to SDS can be used to identify gene products and to recognize heterodimers formed between products of more than one gene.

Alkaline Phosphatase↗