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)

The alkaline phosphatase signal peptide participates in transport of the enzyme to the periplasmic space of Escherichia coli. The signal sequence, like that of other signal peptides, is composed of a polar amino-terminal segment, a central region rich in hydrophobic residues and a carboxy-terminal region recognized by signal peptidase. We have previously shown that an alkaline phosphatase signal peptide mutant containing a polyleucine core region functions efficiently in transport of the enzyme [D. A. Kendall, S. C. Bock, and E. T. Kaiser (1986) Nature 321, 706-708]. In this study, some of the amino acid changes involved in the polyleucine sequence are examined individually. A Phe to Leu substitution as the sole change results in impaired transport properties in contrast to when it is combined with three other amino acid changes in the polyleucine-containing sequence. A mutant with a Pro to Leu substitution in the hydrophobic core region is comparable to wild type while the same type of substitution (Pro to Leu) in the carboxy-terminal segment results in substantial accumulation of the mutant precursor. Finally, introduction of a basic residue into the hydrophobic segment (Leu to Arg substitution) results in a complete export block. These results exemplify the spectrum of properties produced by individual residue changes and suggest there is some interplay between hydrophobicity and conformation for signal peptide function.
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PMID:A comparative analysis of single- and multiple-residue substitutions in the alkaline phosphatase signal peptide. 218 83

SecY is an Escherichia coli integral membrane protein required for efficient translocation of other proteins across the cytoplasmic membrane; it is embedded in this membrane by the 10 transmembrane segments. Among several SecY-alkaline phosphatase (PhoA) fusion proteins that we constructed previously, SecY-PhoA fusion 3-3, in which PhoA is fused to the third periplasmic region of SecY just after the fifth transmembrane segment, was found to be subject to rapid proteolytic processing in vivo. Both the SecY and PhoA products of this cleavage have been identified immunologically. In contrast, cleavage of SecY-PhoA 3-3 was barely observed in a lep mutant with a temperature-sensitive leader peptidase. The full-length fusion protein accumulated in this mutant was cleaved in vitro by the purified leader peptidase. A sequence Ala-202-Ile-Ala located near the proposed interface between transmembrane segment 5 and periplasmic domain 3 of SecY was found to be responsible for the recognition and cleavage by the leader peptidase, since a mutated fusion protein with Phe-Ile-Phe at this position was no longer cleaved even in the wild-type cells. These results indicate that SecY contains a potential leader peptidase cleavage site that undergoes cleavage if the PhoA sequence is attached carboxy terminally. Thus, transmembrane segment 5 of SecY can fulfill both of the two important functions of the signal peptide, translocation and cleavage, although the latter function is cryptic in the normal SecY protein.
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PMID:SecY, a multispanning integral membrane protein, contains a potential leader peptidase cleavage site. 218 44

We detected in urine by HPLC two enzyme fractions of alkaline phosphatase (AP, EC 3.1.3.1), soluble and particulate, analogous to those in serum. The second fraction was eluted with high-salt-content eluent at the same elution time as high-molecular-mass, or particulate, AP in serum. AP characterization in urine from a patient with acute rejection crisis showed a greater sensitivity of the particulate form to treatment with L-phenylalanine, which suggests a higher content of intestinal-type AP in the particulate form. The soluble fraction showed a more liver-type AP behavior. Changes in the chromatograms after the sample was treated with 1-butanol and Triton X-100 support a membrane origin of the particulate AP. Urinalyses from patients with acute renal disease showed increased activity of soluble and particulate AP, with a relatively greater increase of particulate AP.
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PMID:Particulate (high-molecular-mass) and soluble alkaline phosphatase in urine determined by high-performance liquid chromatography. 224 72

We have investigated the actions of human PTH [hPTH-(1-34)] on the association of 45Ca2+ with two human (SaOS-2 and MG-63) and two rat (ROS 17/2.8 and UMR-106) osteoblast-like cell types. In SaOS-2 cells, hPTH-(1-34) binds to specific membrane receptors to activate adenylate cyclase. Treatment of SaOS-2 cells with hPTH-(1-34) resulted in an increase in 45Ca2+ uptake, in a dose-dependent fashion, up to 2- to 4-fold above control values. The increase was first evident at 10 min and persisted for at least 30 min. Treatment with nimodipine, a calcium channel antagonist, was without effect on the stimulatory action of PTH. A similar enhancement of cell-associated 45Ca2+ was observed when the cells were incubated with vasoactive intestinal peptide, which acts via different receptors to activate adenylate cyclase in SaOS-2 cells. Treatment with (Bu)2cAMP also induced an increase in cell-associated 45Ca2+. Pretreatment of SaOS-2 cells with hPTH-(1-34) for 4 h, which induced homologous desensitization to a second challenge with the same peptide for stimulation of cAMP production, did not attenuate the further enhancement of cell-associated 45Ca2+ by a second treatment with hPTH-(1-34). We then examined a possible relationship between alkaline phosphatase (ALPase) and 45Ca2+ uptake. SaOS-2 cells contained high levels of alkaline phosphatase activity and continuously released the enzyme into the medium. Release was enhanced by treatment with hPTH-(1-34) for 10 min. Incubation of cells with levamisole (an inhibitor of the liver/bone/kidney type of ALPase) resulted in a rapid decrease in basal and PTH-stimulated 45Ca2+ uptake, while treatment with L-Phe-Gly-Gly (an inhibitor of human placental ALPase) was without effect. Treatment of the cells with ALPase (bovine kidney) enhanced 45Ca2+ uptake. In MG-63 cells, a stimulatory effect of hPTH-(1-34) on cell-associated 45Ca2+ was also observed; however, hPTH-(1-34) did not stimulate cAMP production in MG-63 cells. In ROS 17/2.8 cells, neither hPTH-(1-34) nor rat PTH-(1-34) stimulated an increase in cell-associated 45Ca2+, while in UMR-106 cells, rat PTH-(1-34) and (Bu)2cAMP did enhance 45Ca2+ uptake, although hPTH-(1-34) was without effect. We conclude that PTH can stimulate an increase in cell-associated 45Ca2+ in several osteoblast-like cell lines, possibly by modulating local ALPase activity; however, this action of PTH does not appear to be obligatorily dependent on the adenylate cyclase-stimulating action of PTH.
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PMID:Stimulation by parathyroid hormone of 45Ca2+ uptake in osteoblast-like cells: possible involvement of alkaline phosphatase. 231 51

We evaluated plasma amino acid (AA) concentrations associated with a histologically defined lesion caused by bile duct ligation (BDL) in developing rats. Nineteen rats that underwent BDL at 14 days of age had marked bile duct proliferation with bridging fibrosis, multifocal lobular necrosis, and minimal polymorphonuclear periportal infiltrate in their livers at sacrifice (11-31 days after ligation). These were compared to two age-matched control groups: 21 nonoperated rats and 22 sham-operated rats; and eight rats with cirrhosis caused by carbon tetrachloride. Signs of liver damage including jaundice, growth failure, bleeding, and ascites were accompanied by elevated bilirubin, ammonia, aspartate aminotransferase (AST), and alkaline phosphatase levels in BDL rats compared to controls. They had higher concentrations of total AAs, phenylalanine, tyrosine, and cyst(c)ine when compared to controls and to CCl4-treated rats. Micronodular cirrhosis was present in CCL4-treated rats with elevated AST and alkaline phosphatase levels. Glutamine and glutamate levels were higher in them than in BDL rats or controls, and branched chain AA levels were lower. These two chronic lesions, one obstructive and one hepatotoxic, both result in fibrotic change, but their metabolic abnormalities as reflected in plasma AA levels are distinct. We found that BDL is an appropriate model with which to study metabolic changes and growth failure due to chronic biliary stasis during its progression to frank cirrhosis.
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PMID:Plasma amino acids in long-term models for obstructive versus toxic liver injury in developing rats. 232 99

In the midgut tissue of the silkworm, Bombyx mori, alkaline phosphatase isozymes, membrane-bound (m-ALP) and soluble (s-ALP) forms are controlled by non-allelic genes on the same chromosome. We purified and characterized both ALPs to elucidate their possible functions and to compare with mammalian ALPs. Both forms were found to be similar Mr = 68,000 in gel permeation chromatography and as a single subunit as a monomer in SDS-polyacrylamide gel electrophoresis with Mr = 58,000 for m-ALP and Mr = 61,000 for s-ALP. The pH optima of ALPs were 10.9 (m-ALP) and 9.8 (s-ALP), and the former was extremely stable even in pH 10-12 which accords with the physiological milieu in Bombyx midgut lumen. Both ALPs had similar substrate specificities. L-cysteine inhibited strongly both ALPs, but inhibitory effects of L-phenylalanine, L-homoarginine, and L-leucine were undetectable for s-ALP and very weak for m-ALP. The antibody raised against purified m-ALP recognized m-ALP but not purified s-ALP and vice versa. Rocket-immunoassay showed that m-ALP was distributed in similar levels along the length of midgut except for the most anterior portion. Seventy percent of s-ALP activity existed in the last one-third of midgut. Immunohistochemical study revealed that the m-ALP was localized at the brush border of columnar cells in the middle and posterior midgut epithelia. In contrast, the s-ALP was localized at the apical surface of goblet cells through the length of midgut. We detected ATPase activity in the purified s-ALP preparation; Mg2+ was essential for the ATPase activity and the activity also increased with KHCO3 but not with KCl. The solubilization test of m- ALP with various agents was attempted and the relationship between m-ALP and the digestive fluid-ALP was discussed.
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PMID:Genetically defined membrane-bound and soluble alkaline phosphatases of the silkworm: their discrete localization and properties. 239 71

The activity of gamma-glutamyl transpeptidase (GGT) and the proportion of alkaline phosphatase (ALP) activity that remains in cell-free amniotic fluid (AF) after inhibition by amino acids ("residual ALP activity") have been evaluated as possible prenatal diagnostic tests for cystic fibrosis. A total of 1511 AFs were examined. In 1435 "reference" AFs (excluding those from pregnancies with a known fetal abnormality and those with a known one in four risk of cystic fibrosis) at 14-24 weeks' gestation, the mean residual ALP activity in the presence of 2.5 mmol/L L-phenylalanine was 32% (median, 28%) and in 10.0 mmol/L L-homoarginine it was 70% (median, 72%). AFs were arbitrarily considered to be "abnormal" if the residual activity was greater than 50% in L-phenylalanine and less than 50% in L-homoarginine. An abnormal residual ALP activity pattern was found in nine of 27 pregnancies which resulted in a neural tube (or other developmental) defect and in five of the 10 pregnancies with a chromosomal abnormality; a further 23 (1.6%) abnormal patterns occurred in the 1435 reference AFs from pregnancies that were believed to have had a normal outcome. However, of an additional 23 AFs that were sampled at the 25th week of pregnancy or later, 13 had an abnormal residual activity pattern; the outcome at term in each case was normal. The residual activity of ALP in the presence of either inhibitor did not change with increasing gestational age. However, the absolute amount of ALP that was inhibited by L-phenylalanine (the so-called "phe-inhibitable activity") was greatest at 18 weeks. GGT activity decreased with increasing length of gestation. Of the AF samples from 16 pregnancies at one in four risk for cystic fibrosis that were obtained at 18 weeks' gestation, 11 AFs had a normal residual ALP activity pattern, normal GGT and normal phe-inhibitable ALP activity. Of these 11, five have come to term and the infants are not affected by cystic fibrosis. Three of the 16 AFs had an abnormal residual ALP activity pattern, low GGT and low phe-inhibitable ALP activity; these pregnancies were assessed to be affected by cystic fibrosis and termination was chosen in each case. The two remaining AFs had borderline, paradoxical GGT and residual ALP activity, and initially could not be classified clearly into either of the two groups; however, phe-inhibitable ALP activity was low in each. These pregnancies are continuing.
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PMID:Microvillar enzymes in amniotic fluid. Considerations for the prenatal diagnosis of cystic fibrosis. 241 95

Alkaline phosphatase activity in rat hepatoma cells (R-Y121B) cultured in a monolayer at 0.5% serum was enhanced by serum, bovine serum albumin, casein and gamma-globulin, but ovalbumin, polyvinylpyrrolidone, dexamethasone, insulin and dibutyrylcyclic AMP showed little effect on alkaline phosphatase activity. In addition, cycloheximide, actinomycin D, chloroquine, dinitrophenol and potassium cyanide also increased the enzyme activity, although the incorporation of [14C]leucine into cellular proteins was almost completely inhibited in the presence of these cytotoxic substances. When R-Y121B cell homogenates were incubated at 37 degrees C, alkaline phosphatase activity increased in a pH-dependent manner: the maximal increase was observed at pH 7.1. The magnitudes of the increase differed among cell homogenates and a 4- to 10-fold increase was observed. Alkaline phosphatase in R-Y121B cells was apparently heat-stable, but that in the cells obtained from various treatments was heat labile and the latter activity decreased to less than 50% of the initial activity after 15 min of incubation at 56 degrees C. Alkaline phosphatase in the control and also in the treated cells was more sensitive to L-homoarginine than L-phenylalanine. The Lineweaver-Burk plot showed that the increases in the enzyme activity were accompanied by changes not only in V but also in Km for alkaline phosphatase reaction. Finally, it has been suggested that the increases in alkaline phosphatase activity under various conditions are due to the conversion of the molecule with a low enzyme activity to the molecule with a high enzyme activity in R-Y121B cells.
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PMID:Regulation of alkaline phosphatase activity in rat hepatoma cells. Effects of serum proteins, cycloheximide, actinomycin D, chloroquine, dinitrophenol and potassium cyanide. 241 85

Human neoplastic salivary cell line (HSGc) and its subclones express alkaline phosphatase (AP) which is sensitive to L-phenylalanine but insensitive to L-homoarginine. Electrophoretic analysis demonstrates two distinct bands of AP, one (sb-1) is heat-stable and another (sb-2) is rather heat-labile and faster mobility than sb-1. The AP activity, especially sb-2, shows high level in less-differentiated clone (HSGc-C5) with increased growth rate but low level in nontumorigenic and well-differentiated clone (HSGc-E1) as compared to parent HSGc. This may suggest that the AP is a possible marker for identification of undifferentiated state in HSGc. This study also indicates that dibutyryl cAMP produces an increase of heat-labile AP in these clones.
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PMID:Different expression of alkaline phosphatase in subclones of human neoplastic salivary duct cell line. 242 79

The optimum pH of serum alkaline phosphatase (alk. P., EC 3.1.3.1) was investigated in adult male rats, mice and rabbits after fasting or after the induction of cholestasis by a single oral dose of 200 mg/kg alpha-naphthylisothiocyanate (ANIT). The nature of serum alk.P. was also studied with the inhibitory effects of three L-amino acids (L-phenylalanine, L-homoarginine and L-cystine) and by electrophoresis. In the rat, fasting as well as ANIT-treatment shifted the optimum pH of alk.P. from 9.4 to 10.0 due to a decrease in intestinal isoenzymes or due to newly appeared liver isoenzymes, while no shifting occurred in mouse and rabbit.
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PMID:The optimum pH of serum alkaline phosphatase after induced cholestasis in the male rat, mouse and rabbit. 246 92


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