Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.3.1 (alkaline phosphatase)
47,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ugp-dependent transport system for sn-glycerol-3-phosphate has been characterized. The system is induced under conditions of phosphate starvation and in mutants that are constitutive for the pho regulon. The system does not operate in membrane vesicles and is highly sensitive toward osmotic shock. The participation of a periplasmic binding protein in the transport process can be deduced from the isolation of transport mutants that lack the binding protein. As with other binding protein-dependent transport systems, this protein appears to be necessary but not sufficient for transport activity. The isolation of mutants has become possible by selection for resistance against the toxic analog 3,4-dihydroxybutyl-1-phosphonate that is transported by the system. sn-Glycerol-3-phosphate transported via ugp cannot be used as the sole carbon source. Strains have been constructed that lack alkaline phosphatase and glycerol kinase. In addition, they are constitutive for the glp regulon and contain high levels of glycerol-3-phosphate dehydrogenase. Despite the fact that these strains exhibit high ugp-dependent transport activity for sn-glycerol-3-phosphate they are unable to grow on it as a sole source of carbon. However, when cells are grown on an alternate carbon source, (14)C label from [(14)C]sn-glycerol-3-phosphate appears in phospholipids as well as in trichloroacetic acid-precipitable material. The incorporation of (14)C label is strongly reduced when sn-glycerol-3-phosphate is the only carbon source. In the presence of an alternate carbon source, this inhibition is relieved, and sn-glycerol-3-phosphate transported by ugp can be used as the sole source of phosphate.
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PMID:Characteristics of a binding protein-dependent transport system for sn-glycerol-3-phosphate in Escherichia coli that is part of the pho regulon. 704 85

A group of male rabbits was starved for 7 days. Their blood samples were collected, before and after the starvation period. Six rabbits were slaughtered for the recovery of livers, while the rest were refed for the next 7 days, at the end of which their blood samples were collected and livers taken out for various analyses. After 7 days of starvation, the total leukocytic count, haemoglobin, bilirubin, proteins and glucose contents, and activities of alkaline phosphatase and glutamate pyruvate transaminase of blood serum decreased significantly, while its lactate dehydrogenase activity and cholesterol, total lipids and urea contents showed a significant increase. In liver, except for the bilirubin and glucose contents, all the biochemical components--RNA, DNA and total proteins included--showed highly elevated values. Refeeding of the starved rabbits tended to normalize most within 7 days. Although RNA, DNA, total proteins, cholesterol and urea contents did not reach the normal level in liver during this period, they were definitely less than those of the starved condition. The hepatic transaminases activities and lipid content in starved + refed livers were considerably decreased during the refeeding period. The histological parameters were slow to recover.
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PMID:Effect of starvation and refeeding on the blood and liver of domesticated rabbits. 717 Sep 91

The yeast S. cerevisiae imports cytosolic components into the vacuole non-selectively by autophagy and degrades them by vacuolar hydrolases under nutrient starvation conditions. We developed a novel system for monitoring autophagy by constructing cells in which modified vacuolar alkaline phosphatase is expressed as an inactive precursor form in the cytosol. Under starvation conditions, the processing of the precursor to the mature form and phosphatase activity appeared gradually, and the mature form was located in the vacuole. Disruption of APG1, an essential gene for autophagy, resulted in no processing or phosphatase activity. These results indicate that the precursor form in the cytosol is transferred to the vacuole by autophagy and converted to the active form by vacuolar proteinases. Thus, autophagy could be determined easily and accurately by measuring the phosphatase activity.
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PMID:Novel system for monitoring autophagy in the yeast Saccharomyces cerevisiae. 774 31

The phoE promoter region in Escherichia coli contains a -10 region, typical of sigma 70-dependent promoters and, instead of a normal -35 region, a so-called pho box, to which the transcriptional activator phospho-PhoB binds under low phosphate conditions. A second pho box is present upstream of the first one and is required for full expression of phoE during phosphate starvation. To determine whether the lack of expression under high phosphate conditions is due solely to the absence of a genuine -35 box, the -10 region was further optimized towards the consensus -10 sequence and promoter activity was measured using alkaline phosphatase as a reporter. The mutations resulted in a drastic increment in the basal level of expression under high phosphate conditions, indicating that the deviations from consensus in the -10 region also play a role in determining the poor expression of the wild-type promoter under these conditions. The expression under high phosphate conditions was partly dependent on the presence of the phoB gene, showing that a small amount of active PhoB must be present under these circumstances. During phosphate starvation, the activity of the mutant promoters was further induced. The upstream pho box was not required for full expression from the mutant promoters under these conditions. Apparently, the wild-type phoE promoter is carefully balanced by deviations from the optimal Pribnow box sequence that reduce expression under high phosphate conditions and by the presence of several copies of the pho box, which enhance expression under phosphate starvation.
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PMID:Effect of mutations in the -10 region of the phoE promoter in Escherichia coli on regulation of gene expression. 781 30

Polyphosphate metabolism in Escherichia coli was studied in order to determine the role of polyphosphates in energy and phosphate metabolism. Phosphate-shift experiments were performed on wild-type E. coli W3110 and on an E. coli strain mutant in the genes encoding the polyphosphate-metabolizing enzymes polyphosphate kinase (PPK) and polyphosphatase (PPX). The levels of polyphosphates were measured by [31P]NMR, and the activities of PPK and PPX were measured using enzymatic assays. During phosphate starvation, the intracellular level of polyphosphate was not detectable in E. coli W3110; the activities of PPX and alkaline phosphatase were high relative to those during exponential growth. During the shift from phosphate starvation to phosphate surplus conditions, PPX activity decreased and PPK activity and intracellular polyphosphate stores increased dramatically. These results imply an important role for polyphosphates in cellular energy and phosphate storage and in adaptation to adverse growth conditions.
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PMID:Polyphosphate metabolism in Escherichia coli. 783 34

The iron starvation-induced, 2,042-amino-acid protein HMWP2 of Yersinia enterocolitica has two internal hydrophobic segments which might promote its export and association with the cytoplasmic membrane. To determine whether part of HMWP2 could be exported beyond the periplasmic face of the cytoplasmic membrane, we used TnphoA mutagenesis to construct 10 hybrid proteins in which periplasmic alkaline phosphatase (PhoA) was fused to the end of C-terminally truncated HMWP1 (at amino acid positions 1751 and 1753 two independent isolates]) had high alkaline phosphate activity (close to that of the native enzyme), both in Escherichia coli and in Y. pseudotuberculosis, indicating that the PhoA segment of the hybrid reached the periplasm. Deletion studies showed that the export signal resides in the second hydrophobic segment of HMWP2. This result would be compatible with the topology of the protein in the cytoplasmic membrane predicted from the distribution of charged amino acids at either end of the two hydrophobic segments. However, two hybrids in which the junction was even further toward the C terminus of HMMWP2 (at positions 1793 and 1999) had only weak alkaline phosphatase activity, suggesting that the predicted topology is incorrect. The location of HMWP2 was therefore determined by subcellular fractionation. The results indicate that HMPW2 is mainly cytoplasmic, consistent with its presumed role in the ATP-dependent, nonribosomal synthesis of an unknown peptide. We propose that the high alkaline phosphatase activity associated with some of the HMWP-2-PhoA hybrids results from the unmasking of the cryptic export signal activity in the second hydrophobic segment of HMPW2.
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PMID:Yersinia spp. HMWP2, a cytosolic protein with a cryptic internal signal sequence which can promote alkaline phosphatase export. 789 1

We have isolated two transposon insertion mutations of the pst-phoU operon which result in the constitutive expression of the phoA gene product, alkaline phosphatase. The two mutations also render Escherichia coli invasive towards cultured HEp-2 cells and define a novel Pho-regulated invasion pathway. The presence of the large 'invasion' plasmid derived from an entero-invasive E. coli (EIEC) clinical isolate in these mutants leads to enhanced invasiveness toward cultured HEp-2 cells, a phenomenon referred to as the 'hyper-invasive' phenotype. Transduction of a pst-phoU insertion mutation into clinical isolates of EIEC and Shigella flexneri results in constitutive PhoA expression and coupled hyper-invasiveness in the former but not the latter. We speculate that the Pho-regulated invasion pathway described here, while silent in bacteria grown in standard laboratory rich media, may become functional in the host when invasive bacteria encounter nutrient starvation and/or other related stress conditions.
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PMID:Hyper-invasive mutants define a novel Pho-regulated invasion pathway in Escherichia coli. 793 62

Bacillus subtilis has an alkaline phosphatase (APase) gene family composed of at least four genes. All members of this gene family are expressed postexponentially, either in response to phosphate starvation or sporulation induction or, in some cases, in response to both. The phoA gene (formerly called phoAIV) and the phoB gene (formerly called phoAIII) products have both been isolated from phosphate-starved cells, and a mutation in either gene decreased the total APase expressed under phosphate starvation conditions. Data presented here show that a phoA phoB double mutant reduced APase production during phosphate starvation by 98%, indicating that these two genes are responsible for most of the APase activity during phosphate-limited growth. The promoter for phoA was cloned and used, with the phoB promoter, to examine phosphate regulation in B. subtilis. phoA-lacZ reporter gene assays showed that the expression of the phoA gene commences as the culture enters stationary phase as a result of limiting phosphate concentrations in the growth medium, thereby mimicking the pattern of total APase expression. Induction persists for approximately 2 h and is then turned off. phoA is transcribed from a single promoter which initiates transcription 19 bp before the translation initiation codon. PhoP and PhoR are members of the two-component signal transduction system believed to regulate gene expression in response to limiting phosphate. The expression of phoA or phoB in response to phosphate starvation was equally dependent on PhoP and PhoR for induction. lacZ-promoter fusions showed that both phoA and phoB were hyperinduced, or failed to turn off induction after 2 h, in a spo0A strain of B. subtilis. Mutations in genes which are required for phosphorylation of Spo0A, spo0B and spo0F, also resulted in phoA and phoB hyperinduction, suggesting that phosphorylation of Spo0A is required for the repression of both APases in wild-type strains. The hyperinduction of either APase gene in a spo0A strain was dependent on PhoP and PhoR. Analysis of a phoP-lacZ promoter fusion showed that the phoPR operon is hyperinduced in a spo0A mutant strain, suggesting that Spo0A approximately P represses APases by repressing phoPR transcription. We propose a model for PHO regulation in B. subtilis whereby the phoPR operon is transcribed in response to limiting phosphate concentration, resulting in activation of the PHO regulon transcription, including transcription of phoA and phoB. When the phosphate response fails to overcome the nutrient deficiency, signals for phosphorylation of Spo0A result in production of Spo0A approximately P, which represses transcription of phoPR, thereby repressing synthesis of the PHO regulon.
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PMID:Sequential action of two-component genetic switches regulates the PHO regulon in Bacillus subtilis. 811 74

Phycobilisomes are the multiprotein complexes predominantly responsible for harvesting light energy in cyanobacteria and some eukaryotic algae. When the cyanobacterium Synechococcus sp. strain PCC 7942 is deprived of an essential nutrient, the phycobilisomes are specifically and rapidly degraded. Degradation may be either partial (after phosphorus deprivation) or complete (after sulfur or nitrogen deprivation). We have developed a visual screen to obtain mutants unable to degrade their phycobilisomes upon nutrient starvation. Complementation of one of these mutants led to the identification of a gene, designated nblA, that encodes a 59 amino acid polypeptide essential for phycobilisome degradation. Transcription of nblA increases dramatically in sulfur- or nitrogen-deprived cells and moderately in phosphorus-deprived cells. Using the phosphorus-regulated alkaline phosphatase (phoA) promoter as a tool, we engineered constructs from which we could control the expression of either sense or antisense nblA. Increased expression of sense nbLA caused complete phycobilisome degradation during phosphorus deprivation, while expression of antisense nblA prevented phycobilisome degradation. Hence, nblA is necessary, and may be sufficient, for the degradation of phycobilisomes under adverse environmental conditions. Further investigation of the mechanism by which nblA causes phycobilisome destruction may reveal general principles that govern the specificity of macromolecular complex degradation.
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PMID:A small polypeptide triggers complete degradation of light-harvesting phycobiliproteins in nutrient-deprived cyanobacteria. 813 38

The effects of short-term starvation on serum and tissue levels of zinc, metallothionein (MT), and the activity of alkaline phosphatase (EC 3.1.3.1, ALP) were investigated with 6-month-old rats. The rats were fed a diet with adequate zinc (92mg/kg of Zn, 1.12% phytic acid) before they were starved for 0h (control), 12h, 24h, and 36h and then killed by decapitation. Fasting was accompanied by typical changes in serum parameters such as reduced glucose and protein concentrations, elevated ketogenesis, and a rapid breakdown of liver glycogen. Fasting did not alter serum zinc levels, but it did lead to a significant elevation in the percent of unsaturated serum-zinc binding capacity. Liver concentrations of zinc and MT, based both on fresh and dry weight, were increased throughout starvation. However, total liver zinc was reduced by up to 23% in response to fasting and total liver MT was slightly elevated. The increased concentrations of liver zinc and MT are, therefore, mainly a consequence of reduced liver weight. A part of the liver zinc, however, was bound to newly synthesized MT to prevent greater zinc loss. Starvation evoked no altered mucosa MT levels. Changes in kidney zinc and kidney medulla MT caused by starvation were small and not significant. In contrast to this observation some variation of kidney cortex MT was apparent. Starvation produced a permanent reduction of the serum and intestinal activity of ALP. In the liver and the medulla of the kidneys no significant differences of ALP activity could be observed. However, kidney cortex ALP was induced after 36h of fasting.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Zinc metabolism in fasted rats. 815 85


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