Differential inhibition of the products of the human alkaline phosphatase loci

Changes in alkaline-phosphatase isoenzymes of hard tissue origin during facial development in the rat

Non-specific alkaline phosphatase (APase) activity was demonstrated histochemically in the hard-tissue-forming areas of the developing rat face from the 14th embryonic day. Isoenzyme distribution of APase was recorded by isoelectric focusing. Three APase isoenzyme bands with lower isoelectric points than adult forms were recorded. Inhibition studies with levamisole dexamisole, L-p-bromotetramisole, D-p-bromotetramisole, diphosphonates and urea showed the embryonic isoenzymes to have the same sensitivity as the adult forms except to urea. Heated to 56 degrees C, both embryonic and adult APase were rapidly inactivated. The differences between the embryonic and adult forms of APase may represent the expression of different gene loci or a difference in post-translational modification.

Human placental alkaline phosphatase in liver and intestine

Three distinct forms of human alkaline phosphatase, presumably isozymes, are known, each apparently associated with a specific tissue. These are placental, intestinal, and liver (kidney and bone). We have used a specific immunoassay and HPLC to show that placental alkaline phosphatase is also present in extracts of liver and intestine in appreciable amounts.

Biochemical and immunological characterization of mutant L-M cells with altered levels of dibutyryl cyclic AMP-inducible alkaline phosphatase

Phosphotyrosine-Sepharose 4B was synthesized and used to purify L-cell alkaline phosphatase. Antibodies to this enzyme interacted with the alkaline phosphatase of strains A-1-2 and A-3-3, mutants that express the enzyme constitutively. This and thermal stability studies suggest that these mutants contain the same alkaline phosphatase isozyme as their parent strain.

Biochemical and immunological characterization of mutant L-M cells with altered levels of dibutyryl cyclic AMP-inducible alkaline phosphatase

Phosphotyrosine-Sepharose 4B was synthesized and used to purify L-cell alkaline phosphatase. Antibodies to this enzyme interacted with the alkaline phosphatase of strains A-1-2 and A-3-3, mutants that express the enzyme constitutively. This and thermal stability studies suggest that these mutants contain the same alkaline phosphatase isozyme as their parent strain.

Cytogenetic analyses utilizing various clastogens in two sibs with Fanconi anemia, their relatives, and control individuals

Structural chromosome damage, sister chromatid exchange (SCE), and proliferation kinetics were studied on lymphocyte cultures from the peripheral blood of two sibs exhibiting signs of Fanconi anemia, their relatives, and control individuals. While the rate of spontaneous chromosome breakage was at the lower limit of that known for Fanconi anemia in our patients, a distinctly greater increase than in controls of breakage frequency could be induced by isoniazid (INH), 4-nitroquinoline-1-oxide (NQO), and diepoxybutane (DEB) in their lymphocytes. Increased aberration frequencies as compared with controls were also observed in the clastogen-exposed lymphocyte cultures of the parents of both sibs, but in some experiments (NQO, DEB 24 h) only in the cells of the healthy brother. There was an increase in the breakage rate of bromodeoxyuridine (BrdU)-labeled consecutive mitoses under the action of NQO, but a decrease with INH as the test clastogen. No significantly higher SCE frequency was found throughout the study in untreated and clastogen-exposed FA lymphocytes as compared with the respective controls. Proliferation was clearly inhibited by INH and NQO as indicated by a distinct increase of the percentage of BrdU-labeled first and a drastic decrease of third metaphases. The present test clastogens were shown not only to be suitable for ensuring the diagnosis of FA in patients with a low incidence of spontaneous breakage but also for determining clastogen-sensitive heterozygotes. According to these results cross-link repair cannot be the only mechanism affected by the basic defect of Fanconi anemia.

Prenatal diagnosis of cystic fibrosis. I. Prospective study of 51 pregnancies

A prenatal diagnosis was performed in 51 pregnancies with a 1-in-4 risk of having a child with cystic fibrosis. The criteria for determining an affected fetus were based on the results of alkaline phosphatase (ALP) residual activity after inhibition by phenylalanine and by homoarginine, of total ALP activity, and of gamma-glutamyltranspeptidase (GGTP) activity in the amniotic fluid taken between 16 and 19 weeks of pregnancy. The chromosomal analysis of amniotic fluid cells showed trisomy 13 in one case which was excluded from the analysis of biochemical assays. The biochemical assays were in the normal ranges in the amniotic fluid of 35 pregnancies: 26 have reached term and a normal infant has been born, 9 are still in progress. A deficiency of the ALP phenylalanine-inhibitable form, depressed values of total ALP and GGTP were observed in the amniotic fluid of 15 pregnancies: one pregnancy went to term and the infant had CF, in 14 cases the pregnancy was terminated, and meconium ileus was observed in ten of these cases. It was observed that the changes towards abnormal values became more significant with advancing gestational age and that 18 weeks appeared to be the optimum time for diagnostic amniocentesis.

Genetic variability of alkaline phosphatase expression in inbred mouse tissues

Quantitative alkaline phosphatase (ALP; EC 3.1.3.1) expression varies among various tissues and among inbred mouse strains. There is about a 20-fold difference in ALP activity in lungs from CBA/J and C57L/J inbred strains and this difference is inherited additively with a heritability of 0.84. Studies of thermostability at 56 and 65 degrees C and sensitivity toward inhibitors (L-phenylalanine, L-homoarginine, L-phenylalanylglycylglycine, and levamisole) do not demonstrate differences in the ALP from lungs or liver of the CBA/J and C57L/J strains. The ALP activity in intestine expressed by the intestinal locus varies over 100-fold between A/J and DBA/1J strains. Further studies of the mechanisms resulting in this difference in ALP activity should help elucidate the mechanisms for aberrant expression of ALP in malignancy and for manipulation of low ALP activity in hypophosphatasia.

Eutopic expression of placental-like alkaline phosphatase in testicular tumors

Very high levels of placental-like alkaline phosphatases (PLAP-like enzymes) were observed in tissues from 13 typical seminomas. Four tumors with seminoma components contained these enzymes to varying degrees, and other testicular tumors had them in smaller or non-detectable amounts. Analysis using monoclonal antibodies produced against the common placental alkaline phosphatase (PLAP) phenotypes and enzyme inhibition studies with amino acids and peptides showed the PLAP-like enzymes present in seminoma to be similar to those PLAP-like enzymes which are expressed in lower amounts in two embryonal carcinomas and in trace amounts in normal testicular tissue. These similarities suggest that the increased expression of PLAP-like enzymes in seminomas results from enhanced eutopic expression of enzymes found in normal testis.

Purification of monoclonal antibodies to human alkaline phosphatases by antigen-immunoaffinity chromatography: comparisons of their molar binding values

Antigen-immunoaffinity chromatography has been used to purify monoclonal antibodies to human alkaline phosphatases. The binding of the purified antibodies to various alkaline phosphatases was tested utilizing an electrophoretic titration assay. The results indicate that binding differences among the various ALPs seen with several of the antibodies are due to antigenic differences in the molecular structure of the enzymes. We define a molar binding value as the minimum molar concentration of antibody necessary to complex all of the ALP in a standard reaction mixture. These values varied widely, indicating marked differences in the avidities of the different antibodies.

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.

Structural analysis of human adult and fetal alkaline phosphatases by cyanogen bromide peptide mapping

The adult and fetal forms of human intestinal alkaline phosphatase (ALPase; orthophosphoric-monoester phosphohydrolase, EC 3.1.3.1) are indistinguishable by a variety of analytical procedures. However, they differ electrophoretically and can be differentiated by binding studies with monoclonal antibodies. In this report, these two enzymes along with placental and liver ALPases are compared by the technique of CNBr peptide mapping, and the role of carbohydrate in generating these patterns is investigated. NaDodSO4/PAGE of CNBr digests of radiolabeled ALPases from fetal and adult intestine shows that these two isozymes share five of seven common-sized CNBr fragments. Placental ALPase shares only one common-sized fragment with either intestinal enzyme. Liver ALPase has no CNBr fragments in common with any of the others. These data indicate that fetal intestinal ALPase is not a heterodimer of one subunit each of intestinal ALPase and placental ALPase as has been postulated. CNBr digests of neuraminidase-treated enzymes reveal a change of mobility of only one CNBr band in each of fetal intestinal, placental, and liver ALPases, indicating the presence of sialic acid residues in these fragments. Periodic acid/Schiff reagent staining (specific for carbohydrate) of CNBr digests of fetal and adult intestinal ALPases reacts with only one band in each enzyme, which is the same band from the fetal enzyme shown to contain sialic acid. However, fetal and adult intestinal ALPases each contain at least one CNBr fragment of unique size that is apparently nonglycosylated.

Studies of the biochemical and immunological properties of human neutrophil alkaline phosphatase with comparison to the established alkaline phosphatase isoenzymes

A range of affinity column chromatographic procedures and various inhibitors have been used to compare human neutrophil alkaline phosphatase with the three established isoenzymes. The column chromatography studies have clearly distinguished neutrophil alkaline phosphatase from the intestinal isoenzyme. Inhibition studies with L-phenylalanine, L-homoarginine and levamisole have revealed a distinct pattern of inhibition for liver, kidney and neutrophil alkaline phosphatase which is quite different from the pattern shown by placental and intestinal alkaline phosphatase. Immunospecificity experiments with a monoclonal antibody raised to human liver alkaline phosphatase have shown that it cross reacts with alkaline phosphatase from kidney, bone and neutrophil. In all studies, neutrophil alkaline phosphatase has virtually identical properties to that of liver, kidney and bone alkaline phosphatase. This is strong evidence that neutrophil alkaline phosphatase is a product of the same structural gene which codes for the liver/bone/kidney group of human alkaline phosphatases.

5-Bromo-2'-deoxyuridine induces placental alkaline phosphatase biosynthesis in cultured choriocarcinoma cells

5-Bromo-2'-deoxyuridine (BrdUrd) stimulated the biosynthesis and hence increased the activity of placental alkaline phosphatase in choriocarcinoma cells. While BrdUrd had no effect on the rate of degradation or processing of placental alkaline phosphatase, it increased the rate of phosphatase synthesis. The stimulation of enzyme activity could be completely accounted for by the increase in alkaline phosphatase protein. Both control and BrdUrd-induced cells contained polypeptides of 61,500 and 64,500 Da, identified as the precursor and fully processed forms of placental alkaline phosphatase monomer. The half-life of this enzyme monomer in both control and BrdUrd-treated cells was estimated to be 36 h. BrdUrd induced a specific increase in the placental alkaline phosphatase mRNA leading to the observed enhancement of biosynthesis. The continued rise in alkaline phosphatase biosynthesis in BrdUrd-induced cells following BrdUrd removal indicated that this analog acted by incorporation into DNA.

Cytochemical and biochemical studies on neutrophil alkaline phosphatase in parents of trisomy 21 children

A study of karyotypes and neutrophil alkaline phosphatase (NAP) was carried out for 66 parents (33 couples) of trisomy 21 children and for 60 control parents (30 couples). Enzyme activity was determined simultaneously by biochemical and cytochemical techniques. In the mothers of trisomy 21 children we found: (a) by biochemical techniques, a significant increase of NAP activity in polymorphonuclear leukocyte (PMN) homogenates (P less than 0.01) and a lower supernatant/pellet ratio (P less than 0.01); (b) by cytochemical techniques (with or without thermal and urea treatments) NAP activity was significantly higher (P less than 0.001) than in control mothers; in the fathers, the two techniques gave normal NAP activity results.

The placenta in leprosy

Eighty-one placentae from women with leprosy and 17 placentae from healthy controls were subjected to a detailed macroscopic, light microscopic, ultrastructural, immunopathological, microbiological and biochemical study. The placental morphology and immunohistology were normal, and there was no morphological evidence of infection of the placenta due to M. leprae. No acid-fast bacilli or acid-fast bacillary granules were seen on light microscopy of any of the placentae from leprous women, although homogenates from two out of seven placentae from women with very active lepromatous leprosy contained acid-fast bacilli in very small numbers. The small placental size of women with leprosy, most marked in those with lepromatous leprosy, appears to be due to a decrease in placental cell size, rather than to a reduced number of cells in the placenta. It is postulated that the small placenta and reduced fetal birth weight observed in lepromatous leprosy are a consequence of depressed maternal immune reactivity.

Monoclonal antibodies against placental-like and intestinal-like alkaline phosphatases in a malignant human cell line

Monoclonal antibodies were raised against alkaline phosphatase (ALP) from the malignant human cell line Hep2, a derivative of HeLa, which was established from a cervical carcinoma. Two forms of ALP are found in Hep2 cells resembling, but not identical to, the normal placental and intestinal ALPs. Seven monoclonal antibodies were raised against Hep2 ALP. All of these reacted nearly identically with normal placental ALP and the placental-like ALP from Hep2 cells. Three of these antibodies exhibited reduced reactivities for either the common type 2 or 3 allelic variants of placental ALP. From these binding studies, the placental-like ALP from Hep2 cells appears to be a slightly modified form of the normal type 1 placental ALP. One of the seven antibodies bound to the adult and fetal intestinal ALPs, but more strongly to the adult form, suggesting that the Hep2 intestinal-like ALP is a form of the normal adult intestinal ALP.

Purification of human adult and foetal intestinal alkaline phosphatases by monoclonal antibody immunoaffinity chromatography

We have used the technique of monoclonal antibody immunoaffinity chromatography to purify adult and foetal intestinal alkaline phosphatases. Pure adult intestinal enzyme was obtained from a crude tissue extract with a single immunoaffinity chromatographic step in yields exceeding 95%. An additional ion-exchange chromatographic step was necessary for purification of the foetal enzyme, but yields still exceeded 70%. Experiments to optimize the efficiency of the monoclonal antibody immunoaffinity chromatography procedure suggest that the relative strength of binding of an antibody to its antigen is the most important factor to consider when constructing such columns. A column made from an antibody of too low an avidity will not retain the enzyme, while one of too high an avidity will make elution of enzyme in the active state difficult. A scheme is suggested for the application of this technique to a general approach to enzyme purification.

Transplacental genetic and cytogenetic effects of alkylating agents in the mouse. I: Induction of somatic coat color mutations

Induction of somatic coat color mutations by the alkylating agents ENU, MNU, EMS, MMS, DES, DMS, and trenimon and by the tuberculostatic drug INH was investigated in the mammalian spot test. Positive results were obtained with EMS (100 mg/kg), ENU (20-60 mg/kg), and INH (100 mg/kg), while trenimon (100 micrograms/kg), DES (225 mg/kg), and MNU (2 mg/kg) yielded inconclusive data. No mutagenic activity was found for MMS (125 mg/kg) and DMS (50 mg/kg). The mutagenic potency of monofunctional alkylating agents at subtoxic doses decreases as follows ENU greater than EMS greater than DES greater than MMS = DMS. The hypothesis that somatic coat color mutations in the mouse are predominantly due to intragenic changes is discussed. Differences in the RS frequency between offspring of the crosses NMRI X DBA and C57 X T are due to differences in loci available for mutation induction. Mutations that uncover the recessive allele p contribute to a significant extent to the total RS frequency observed in the mammalian spot test.

Two monoclonal antibodies recognizing determinants on human embryonal carcinoma cells react specifically with the liver isozyme of human alkaline phosphatase

From a series of hybridomas that produced monoclonal antibodies reactive with the surface of human embryonal carcinoma cells, two that specifically recognized determinants of the liver/bone/kidney isozyme of alkaline phosphatase were isolated. They did not cross-react with the intestinal or placental isozymes. Phylogenetic studies revealed that both antibodies cross-reacted strongly with liver alkaline phosphatase from higher primates, but exhibited marked differences in their respective cross-reactions with liver alkaline phosphatase from other mammalian species.

Amniotic fluid alkaline phosphatase isoenzymes in early prenatal diagnosis of cystic fibrosis

Second-trimester amniotic fluid contains two major alkaline phosphatase (ALP) isoenzymes, one susceptible to inhibition by phenylalanine and the other to inhibition by homoarginine. The proportions of these isoenzymes are constant between 15 and 21 weeks of gestation. In pregnancies where the fetus has cystic fibrosis there is a profound deficiency of the phenylalanine-inhibitable form which is thought to be derived mainly from mucosal cells of the fetal intestine. When phenylalanine and homoarginine were used to define ALP isoenzymes in stored amniotic fluids, 9 of 10 cases of cystic fibrosis were identified, while only 9 of 831 control fluids were scored as false positives. In pregnancies where there is an a priori risk of 1:3 (one or more previous affected children) a positive test indicates a 28:1 risk of cystic fibrosis in the fetus. This method is likely to prove satisfactory for the early prenatal diagnosis of cystic fibrosis.

Antigenic determinants of human placental and testicular placental-like alkaline phosphatases as mapped by monoclonal antibodies

Placental alkaline phosphatase (PLAP) in humans shows a high degree of genetic polymorphism as disclosed by electrophoretic analysis. Human testes contain trace amounts of a PLAP-like enzyme, that although immunologically cross-reactive with PLAP, shows unique catalytic properties. As an alternative approach to study enzyme polymorphism we have developed monoclonal antibodies to purified allelic variants of PLAP. Five different monoclonal antibodies are described in this report. The antibodies react with different epitopes on the PLAP molecule. Both conformational dependent and independent determinants are detected. Two epitopes are modified when comparing the S and F allelic variants of PLAP. One epitope is common to PLAP and the intestinal isoenzyme of alkaline phosphatase. The five epitopes appear to be mapped on two rather distant antigenic domains. Combinations of any two antibodies binding to different domains give immunoprecipitates with PLAP on Ouchterlony tests and give good response in sandwich enzyme-linked immunosorbent assays. A study of PLAP-like enzyme in 32 individual testis samples indicates differences in four of the epitopes when compared with PLAP. Four types of testicular enzymes can be distinguished based on their reactivities. These results indicate structural differences between the testicular PLAP-like enzyme and PLAP. These differences are compatible with an underlying genetic mechanism.

Leukocyte alkaline phosphatase: another organ-specific alkaline phosphatase

We have used enzyme specific inhibitors and heat inactivation to distinguish Leukocyte alkaline phosphate (LAP) from other organ-specific alkaline phosphatases as well as to compare LAP from normal granulocytes and leukemic cells with elevated LAP. The heat inactivation and inhibition curves of LAP are quite different from those of other organ-specific alkaline phosphatases. The inhibition curves and heat inactivation characteristics of LAP from normal granulocytes and that obtained from chronic granulocytic leukemia (CGL) blast phase cells with elevated LAP are identical. These data suggest that LAP is distinct from other organ-specific alkaline phosphatases, particularly placental alkaline phosphatase. We also conclude that the LAP present in cells with elevated levels is very similar or identical to that of normal granulocytes.

Dibutyryl cAMP-inducible alkaline phosphatase in animal cell plasma membranes: fluorescence detection of mutant clones on polyester cloth

We have developed a rapid screening assay that allows us to estimate the alkaline phosphatase content of mouse L-M cell colonies immobilized on polyester cloth. This permitted the identification and isolation of two mutant clones with increased constitutive alkaline phosphatase activity and six clones that fail to express this activity when treated with dibutyryl cyclic AMP. Both of the strains with increased constitutive activity have basal enzymatic activities that are 6- to 7-fold higher than the activity of the parental strain. The extents to which the cyclic nucleotide further induces alkaline phosphatase in these two strains are different, however, indicating that they represent two classes of mutants. Studies using amino acids and synthetic peptides as alkaline phosphatase inhibitors suggest that only one alkaline phosphatase isoenzyme predominates, in both the parental and the mutant cell lines, with or without induction by cyclic nucleotide. Comparison to mouse tissues indicates that our cell lines express an isozyme resembling that found in kidney and bone. The six clones that fail to express alkaline phosphatase activity when treated with dibutyryl cyclic AMP also have extremely low basal levels of the enzyme. All of these mutant strains continue to synthesize protein when treated with dibutyryl cyclic AMP and undergo growth cessation and morphological changes in the presence of this agent. Thus, the mutations all appear to affect factors specific to the expression of alkaline phosphatase activity rather than factors that affect general cellular responsiveness or permeability to dibutyryl cyclic AMP. The characterization of these strains may help elucidate mechanisms of eukaryotic membrane protein biogenesis, enzyme induction, and regulation of gene expression by cyclic nucleotides.

Characterization of human foetal intestinal alkaline phosphatase. Comparison with the isoenzymes from the adult intestine and human tumour cell lines

The molecular structure of human foetal intestinal alkaline phosphatase was defined by high-resolution two-dimensional polyacrylamide-gel electrophoresis and amino acid inhibition studies. Comparison was made with the adult form of intestinal alkaline phosphatase, as well as with alkaline phosphatases isolated from cultured foetal amnion cells (FL) and a human tumour cell line (KB). Two non-identical subunits were isolated from the foetal intestinal isoenzyme, one having same molecular weight and isoelectric point as placental alkaline phosphatase, and the other corresponding to a glycosylated subunit of the adult intestinal enzyme. The FL-cell and KB-cell alkaline phosphatases were also found to contain two subunits similar to those of the foetal intestinal isoenzyme. Characterization of neuraminidase digests of the non-placental subunit showed it to be indistinguishable from the subunits of the adult intestinal isoenzyme. This implies that no new phosphatase structural gene is involved in the transition from the expression of foetal to adult intestinal alkaline phosphatase, but that the molecular changes involve suppression of the placental subunit and loss of neuraminic acid from the non-placental subunit. Enzyme-inhibition studies demonstrated an intermediate response to the inhibitors tested for the foetal intestinal, FL-cell and KB-cell isoenzymes when compared with the placental, adult intestinal and liver forms. This result is consistent with the mixed-subunit structure observed for the former set of isoenzymes. In summary, this study has defined the molecular subunit structure of the foetal intestinal form of alkaline phosphatase and has demonstrated its expression in a human tumour cell line.

Diagnostic Value of Intestinal Alkaline Phosphatase in Horse Serum

Antiserum directed against equine intestinal Alkaline Phosphatase (ALP) was produced in rabbits and used to develop a sensitive and quantitative assay for the detection of intestinal ALP in equine serum. This assay was then used to measure the half-life of intravenously injected intestinal ALP and to determine if the intestinal ALP was present in normal horse sera, sera from horses presented for lesions not involving the gastrointestinal tract and sera from horses presented with lesions involving the gastrointestinal tract. The results suggest that intestinal ALP is not likely to appear in equine serum even when gastrointestinal disease is present and, therefore, appears to be of no diagnostic value.

Biosynthesis and processing of placental alkaline phosphatase

Polypeptides of 61,500 and 64,500 apparent molecular weights were the precursor and fully processed forms of placental alkaline phosphatase monomer synthesized by choriocarcinoma cells in vivo. [3H] Mannose was incorporated into both polypeptides whereas [3H] glucosamine was incorporated mainly into the 64,500-dalton polypeptide, suggesting processing by the addition of glucosamine moieties. In the absence of microsomal membranes, choriocarcinoma mRNA directed the cell-free synthesis of the preprotein form of alkaline phosphatase monomer of apparent Mr = 60,000. The unglycosylated monomer had an apparent Mr = 58,000. In the presence of microsomal membranes, the 60,000-dalton polypeptide was processed to a polypeptide of apparent Mr = 61,500, comigrating with the precursor form of alkaline phosphatase monomer.

Measurement of biosynthetic rates and intracellular transit times for a cell-surface membrane glycoprotein, alkaline phosphatase in HeLa cells

The techniques for measurement of biosynthetic rates and intracellular transit times of an integral membrane protein isoenzyme have now been validated. Thus, induction of placental alkaline phosphatase in cultured HeLa cells by prednisolone and by butyrate is shown to result in its increased biosynthesis as measured by uptake of [35S]methionine into immunoprecipitated cell-surface placental alkaline phosphatase. The cell-surface placental alkaline phosphatase is liberated from the cells by proteolytic cleavage by bromelain, which results in a decrease of the placental alkaline phosphatase subunit mass from 64,000 to 62,000 daltons. The time of transit of new placental alkaline phosphatase molecules from their ribosomal site of synthesis to their terminal cell-surface, bromelain-sensitive site is approximately 55 min. This system may be useful in studies of regulation of intracellular protein processing and transport to the cell surface of proteins destined to become integral membrane proteins.

Metal binding by pharmaceuticals. Part 3. Copper (II) and zinc (II) interactions with isoniazid

Formation constants for copper(II) and zinc(II) complexes of isonicotinoylhydrazine (isoniazid) and guanosine-5'-monophosphate have been measured potentiometrically at 37 degrees C, I = 150 mmol dm-3 [NaCl]. These constants have been used in computer models to assess the extent of complex formation by the drug in vivo. The simulations indicate that the predominant complexes existing in blood plasma are ternary species formed with histidinate. However, at clinical levels of isoniazid, it seems unlikely that these complexes are physiologically significant. On the other hand, ternary complex formation with nucleosides may be involved in the binding of isoniazid to viral RNA.

The chromatographic and electrophoretic micro-heterogeneity of alkaline phosphatase of rat dental pulp

Alkaline phosphatase of rat dental pulp was separated into two forms by anion-exchange chromatography, gel-filtration and electrophoresis. The minor activity (AP I) was eluted at 0.1 M of NaCl from a DEAE-cellulose column, and the major activity (AP II) in the broad range of approx. 0.15-0.5 M. These two enzyme activities gave rise to distinct peaks on a TSK-GEL Toyopearl (Fractogel TSK) HW 55-S column and showed different electrophoretic behaviours on both sodium dodecyl sulphate (SDS) and non-SDS polyacrylamide gels. The molecular weights of AP I and AP II were estimated by gel-filtration to be 130,000-150,000 and above 500,000, respectively. On SDS gel electrophoresis, the molecular weight of AP II was changed to 130,000, while AP I had a molecular weight of 150,000. Judging from the sensitivities to heat and some inhibitors, AP I and AP II are biochemically indistinguishable from each other.

A comparison of the alkaline phosphatases of rat dental pulp, bone, kidney, liver and intestine

The sensitivity of the dental pulp enzyme to heat was similar to that of enzymes from bone and kidney; alkaline phosphatases from liver and intestine were more stable to heat. L-Homoarginine strongly inhibited the enzyme activities from pulp, bone, kidney and liver but did not affect intestinal enzyme activity. Increasing the molarity of carbonate buffer or glycine buffer in the assay solution decreased intestinal alkaline phosphatase activity more markedly than enzyme activities of other tissues. In 100 mM glycine-NaOH buffer, the effects of Zn2+, Mg2+ and Ca2+ on pulp alkaline phosphatase activity were similar to those on the enzyme activities of bone, kidney and liver. The electrophoretic pattern of the pulp enzyme on sodium dodecyl sulphate-gels was identical with that of bone enzyme and differed from the patterns of enzymes from other tissues. These results suggest that the dental pulp alkaline phosphatase may be the same as bone enzyme.

Production of a monoclonal antibody to human liver alkaline phosphatase

A monoclonal antibody to human liver alkaline phosphatase (ALP) has been produced by the mouse-hybridoma method using a partially purified enzyme preparation as antigen. The particular hybridoma secreting the antibody was detected by a screening procedure based on the retention of enzyme activity by the enzyme/antibody complex. The antibody cross-reacts strongly with human kidney and bone ALPs but not with human placental or intestinal ALPs. It also cross-reacts with liver and kidney ALPs from gorilla, chimpanzee and orangutan. It shows no significant reaction, under the conditions used, with liver or kidney ALPs from several lower primates. An antibody affinity column was prepared and shown to be effective for the final stages of liver ALP purification.

Cutaneous alkaline phosphatase: a biochemical study

A fluorometric microassay of alkaline phosphatase is described; it is based on the hydrolysis of 4-methylumbelliferyl phosphate and is about three orders of magnitude more sensitive than the usual colorimetric procedures. When applied to skin, the addition of fluoride is necessary to avoid interference from the relatively high levels of acid phosphatase present in the epidermis. Kinetic data for cutaneous alkaline phosphatase are reported. Skin appears to contain a single enzyme of the 'bone-liver-kidney' type, which is present both in a soluble and in membrane-bound form. It occurs almost exclusively in the dermis, not more than 1% of the total alkaline phosphatase of human skin being present in the epidermis.

Demonstration using monoclonal antibodies of inter-locus heteromeric isozymes of human alkaline phosphatase

Monoclonal antibodies were used to demonstrate hybrid forms of human alkaline phosphatase (ALP) composed of subunits from both placental and intestinal loci. Four main isozymes with alkaline phosphatase activity appear on polyacrylamide gels of the HeLa cell line, Hep 2/5 after electrophoresis. The mobilities of all 4 isozymes are retarded after incubating cellular extracts with a monoclonal antibody specific for placental ALP, while the mobilities of 2 isozymes are also affected by a monoclonal antibody which reacts specifically with intestinal ALP. These 2 isozymes, therefore represent interlocus heteromers (placental/intestinal ALP).

A search for trace expression of placental-like alkaline phosphatase in non-malignant human tissues: demonstration of its occurrence in lung, cervix, testis and thymus

A search for placental or placental-like human alkaline phosphatase (ALP) was made in human tissues. The tissue extracts were assayed for ALP before and after heating at 65 degrees C for 1 h. Trace amounts of heat-stable ALP activity (greater than 0.01 IU/g) were found in lung, testis, cervix and thymus. The heat-stable ALP in these four tissues gave in Ouchterlony double diffusion plates lines of apparent identity with placental ALP when a rabbit anti-human placental antiserum was used. Inhibition studies with L-phenyl-alanine (Phe), L-homoarginine (Har), L-phenylalanylglycylglycine (Pgg), L-leucine (Leu) and levamisole (Leva), were carried out on the heat-stable ALP and on the total ALP. The heat-stable ALPs from cervix and lung gave [I]50 values with each inhibitor comparable to those of placental ALP. The heat-stable ALPs froM testis and thymus gave [I]50 values for Leu and Pgg which were significantly different from the placental isoenzyme. Electrophoresis of heat-stable lung ALP from different individuals showed polymorphic differences similar to those seen with placental ALPs. Such differences were not seen with heat-stable testis ALP. We conclude that human non-malignant testis, cervix, lung and thymus tissues contain small amounts of placental or placental-like ALPs. The heat-stable ALPs in cervix and lung appear to have the same characteristics as placental ALP and are probably encoded by the same gene locus. The heat stable ALPs in testis and thymus, though immunologically very similar to placental ALP differ from it in inhibition profile and electrophoretically. The significance of the results in relation to the "ectopic' expression of placental and placental-like ALPs in malignancy is discussed.

The in vitro synthesis and secretion of alkaline phosphatase from first trimester human decidua

We studied the in vitro synthesis and secretion of alkaline phosphatase by human first trimester decidual tissue incubated in organ culture. Decidua synthesizes two different alkaline phosphatase isoenzymes; heat stable and heat labile. decidual tissue maintains a constant pool of alkaline phosphatases. The synthesis of alkaline phosphatase may be the driving force for its secretion. The de novo synthesis and secretion rate of alkaline phosphatases were also investigated. The higher specific radioactivities of the secreted enzymes than those found in the tissue may suggest that newly synthesized alkaline phosphatase is preferentially released. The intracellular distribution of the alkaline phosphatase isoenzymes was compared as well. The characteristics of the two isoenzymes are different in human decidua of maternal origin from those previously reported in the human placenta originating from embryonic stem cells.

Evidence that alkaline phosphatase from human neutrophils is the same gene product as the liver/kidney/bone isoenzyme

Neutrophils were isolated in good yield from fresh whole blood and their alkaline phosphatase was solubilized. Inhibitor studies using L-phenylalanylglycylglycine, L-phenylalanine and L-homoarginine revealed a distinct pattern of inhibition for each of the crude or purified preparations of the human isoenzymes of alkaline phosphatase from liver, intestine or placenta. Aqueous solutions from butanol extracts of human neutrophils and a purified preparation of the enzyme from neutrophils displayed a pattern virtually identical to that of the liver alkaline phosphatase. This is consistent with the proposal that it is the product of the same structural gene which codes for the liver/kidney/bone group of human alkaline phosphatases.

Suppression and reexpression of human intestinal-like alkaline phosphatase in intraspecific hybrids

Expression of the gene locus which codes for a form of human intestinal alkaline phosphatase (ALP) has been analyzed in intraspecific somatic cell hybrids. Hybrids were constructed between D98/AH-2, a line of HeLa which ectopically synthesizes high levels of this ALP isozyme, and three different nonintestinal ALP-producing diploid lines. In chromosomally complete hybrids, expression of the ALP isozyme was initially suppressed, but on extended culture, reexpression occurred, as did limited chromosome loss. Results from extensive subcloning experiments showed that events leading to reexpression occurred at high frequency, and this ALP reexpression appeared to confer some selective advantage, direct or indirect, on the cells. In the fibroblast hybrids, reexpression of the intestinal-like ALP was always accompanied by new, high-level expression of liver/bone/kidney ALP, the product of a separate ALP gene locus. Thus expression of the one ALP locus is not excluded and, in fact, appears to be promoted by expression of the other in these cells.

A monoclonal antibody that reacts with nonallelic enzyme glycoproteins

One of six monoclonal antibodies raised against purified human placental alkaline phosphatase cross-reacts with the adult and fetal forms of intestinal alkaline phosphatase. The placental and intestinal enzymes are nonallelic. A new electrophoretic titration procedure was used to assess the relative reactivities of the different enzymes with the antibody. The placental enzyme was the most reactive. However, the adult intestinal enzyme showed greater reactivity than the fetal enzyme. The determinants to which the antibody binds on these three forms of alkaline phosphatase presumably differ in their detailed molecular configurations.

Evolution of alkaline phosphatases in primates

Alkaline phosphatase [orthophosphoric-monoester phosphohydrolase (alkaline optimum), EC 3.1.3.1] in placenta, intestine, liver, kidney, bone, and lung from a variety of primate species has been characterized by quantitative inhibition, thermostability, and immunological studies. Characteristic human placental-type alkaline phosphatase occurs in placentas of great apes (chimpanzee and orangutan) but not in placentas of other primates, including gibbon. It is also present in trace amounts in human lung but not in lung or other tissues of various Old and New World monkeys. However, a distinctive alkaline phosphatase resembling it occurs in substantial amounts in lungs from Old World monkeys but not New World monkeys. It appears that duplication of alkaline phosphatase genes and mutations of genetic elements controlling their tissue expression have occurred relatively recently in mammalian evolution.

Biochemistry of alkaline phosphatase isoenzymes

The review discusses the similarities and differences between the common isoenzymatic forms of ALP. Methods for separating, measuring, and purifying the isoenzymes on the basis of these differing properties are described. The evidence is reviewed for the existence of different genes coding for different isoenzymes, and the current state of knowledge is surveyed concerning the location, development, function, and regulation of the isoenzymes. Finally, some unusual forms of ALP which may appear in the circulation are described.

A possible new locus of alkaline phosphatase expressed in human testis

Human testes contain trace amounts of heat-stable placental-like alkaline phosphatase. Using a recently described allotype-specific monoclonal antibody (F11) toward placental alkaline phosphatase (PLAP), we show that the frequencies of reactivity of the testis enzymes differ greatly from those of the placental phenotypes. By means of the enzyme inhibitors L-Phe, L-Phe-gly-gly, L-Leu, and L-Leu-gly-gly, the testis enzyme can be clearly distinguished in all cases from the placental enzyme. These results argue that the testis enzyme is not a product of the placental gene and suggest the possible existence of a new locus of alkaline phosphatase.

Alkaline phosphatase activity in cultured meningioma cells

The specific activity of alkaline phosphatase in cultured human meningioma cells varies over a relatively wide range. There is no correlation between the levels of activity and the histological type of meningioma from which the cultures were derived. The enzyme is heat-labile and is strongly inhibited by L-homoarginine, levamisole, and 1-bromotetramisole, but unaffected by L-phenylalanine and L-phenylalanyl-glycylglycine. These findings indicate that meningioma cells synthesize the liver/bone/kidney form of alkaline phosphatase. In contrast to cultures derived from pituitary adenomas, glioblastomas, and astrocytomas in which prednisolone and/or sodium butyrate elicit a manifold increase of alkaline phosphatase activity, with meningioma cells the hormone causes only a slight augmentation in specific activity, and the fatty acid is ineffective. As with other cells producing the liver/bone/kidney enzyme form, no increase in activity occurs in meningioma cells growing in hyperosmolar medium.

Partial characterization of two mouse liver alkaline phosphatases that require manganese for activity

Two manganese requiring isozymes of alkaline phosphatase from the liver of the house mouse (Mus musculus)were studied to determine their properties and location within the cell. 2. The two isozymes, referred to as Region I and Region III, were located in the cytosol from liver homogenates. 3. Optimum activity for Region I isozyme at 37 degrees C was obtained at pH 9.1 and a manganese concentration of 0.5 mM. 4. Optimum conditions for Region III isozyme were pH 7.4 and 5.0 mM manganese. 5. Both isozymes were stable at 56 degrees C; Region III isozyme was stable at 65 degrees C, but Region I isozyme was partially deactivated to 35% of its original activity. 6. Both isozymes were completely deactivated at 75 degrees C within 30 min. Region I isozyme was inhibited by 10 mM L-homoarginine (30% of original activity) and 2.5 mM L-phenylalanine (66% of original activity). 7. No inhibition occurred with Region III isozyme in the presence of either chemical.