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:3.2.1.23 (beta-galactosidase)
14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The number of gene assignments to human chromosome 20 has increased slowly until recently. Only seven genes and one fragile site were confirmed assignments to chromosome 20 at the Ninth Human Gene Mapping Workshop in September 1987 (HGM9). One fragile site, 13 additional genes, and 10 DNA sequences that identify restriction fragment length polymorphisms (RFLPs), however, were provisionally added to the map at HGM9. Five mutated genes on chromosome 20 have a relation to disease: a mutation in the adenosine deaminase gene results in a deficiency of the enzyme and severe combined immune deficiency; mutations in the gene for the growth hormone releasing factor result in some forms of dwarfism; mutations in the closely linked genes for the hormones arginine vasopressin and oxytocin and their neurophysins are probably responsible for some diabetes insipidus; and mutations in the gene that regulates both alpha-neuraminidase and beta-galactosidase activities determine galactosialidosis. The gene for the prion protein is on chromosome 20; it is related to the infectious agent of kuru, Creutzfeld-Jacob disease, and Gertsmann-Straussler syndrome, although the nature of the relationship is not completely understood. Two genes that code for tyrosine kinases are on the chromosome, SRC1 the proto-oncogene and a gene (HCK) coding for haemopoietic kinase (an src-like kinase), but no direct relation to cancer has been shown for either of these kinases. The significance of non-random loss of chromosome 20 in the malignant diseases non-lymphocytic leukaemia and polycythaemia vera is not understood. Twenty-four additional loci are assigned to the chromosome: five genes that code for binding proteins, one for a light chain of ferritin, genes for three enzymes (inosine triphosphatase, s-adenosylhomocysteine hydrolase, and sterol delta 24-reductase), one for each of a secretory protein and an opiate neuropeptide, a cell surface antigen, two fragile sites, and 10 DNA sequences (one satellite and nine unique) that detect RFLPs.
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PMID:The map of chromosome 20. 307 44

Fumarate reductase catalyzes the terminal step of anaerobic electron transport with fumarate as a terminal electron acceptor. Transcription of the fumarate reductase (frdABCD) operon in Escherichia coli is repressed in the presence of the preferred terminal electron acceptors, oxygen and nitrate. To identify trans-acting genes involved in regulation by nitrate, a number of E. coli mutants were generated in which expression of a frdA'-'lacZ protein fusion was no longer fully repressed by nitrate. One of these mutants, strain LK23R35, exhibited 17-fold higher beta-galactosidase activity than the wild-type strain when grown anaerobically in the presence of nitrate. When grown aerobically in the presence of nitrate, it contained three- to fourfold more beta-galactosidase activity than the wild-type strain did. Oxygen regulation of frd expression, however, was unaffected by the mutation, since the level of beta-galactosidase activity in both strains was nearly identical when they were grown in the absence of nitrate either aerobically or anaerobically. To confirm that the mutation acts in trans to frdABCD, we measured fumarate reductase levels and found them to parallel FrdA'-beta-galactosidase activity under all growth conditions tested. The effect of the mutation is pleiotropic, since the levels of nitrate reductase in LK23R35 were not induced by the addition of nitrate. The frdR mutant was also derepressed for nitrate control of the trimethylamine-N-oxide reductase and alcohol dehydrogenase enzymes. The mutation maps in a region between trp and hemA at 27 min on the E. coli chromosome. This gene, where we call frdR, is involved in both positive and negative regulation of electron transport and fermentation associated genes. A cloned 4.9-kilobase fragment of chromosomal DNA was found to complement the frdR mutation; both repression of fumarate reductase gene expression and activation of nitrate reductase gene expression were restored.
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PMID:The frdR gene of Escherichia coli globally regulates several operons involved in anaerobic growth in response to nitrate. 327 62

In order to relate the biogenesis of the lactose transport system to lipid synthesis, a glycerol-requiring mutant of Escherichia coli K-12 with a specific defect in l-glycerol-3-phosphate synthesis was isolated and characterized. The defective enzyme is the biosynthetic l-glycerol-3-phosphate dehydrogenase [l-glycerol-3-phosphate: NAD (P) oxidoreductase, EC 1.1.1.8] which functions as a dihydroxyacetone phosphate reductase to provide l-glycerol-3-phosphate for lipid synthesis. In this mutant, removal of glycerol from the growth medium results in inhibition of the synthesis of protein, deoxyribonucleic acid, and phospholipid. Inhibition of phospholipid synthesis immediately follows glycerol removal, whereas the inhibition of deoxyribonucleic acid and protein synthesis is preceded by a short lag period. Glycerol starvation does not change the turnover pattern of previously synthesized phospholipids. The blocking of lipid synthesis by glycerol starvation causes a drastic decrease in inducibility of beta-galactoside transport activity relative to beta-galactosidase, indicating that induction of lactose transport requires de novo lipid synthesis.
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PMID:Induction of the lactose transport system in a lipid-synthesis-defective mutant of Escherichia coli. 491 67

We have previously shown that the membrane domain of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase from hamster contains all of the sequences required for both localization to the endoplasmic reticulum and regulated degradation of the enzyme. It has been reported that the enzymatic activity and mRNA levels of HMG-CoA reductase from sea urchin embryos cultured in the presence of regulators were unchanged compared to levels in control embryos (Woodward, H.D., Allen, M.C., and Lennarz, W.J. (1988) J. Biol. Chem. 263, 18411-18418). This observation led us to investigate the possibility that the sea urchin enzyme is not subject to regulated protein turnover. Interestingly, the sea urchin enzyme shares 62% amino acid sequence identity with the hamster enzyme in the membrane domain and shares similar predicted topological features. In the current studies we have compared the degradation phenotypes of the sea urchin HMG-CoA reductase and the hamster HMG-CoA reductase in Chinese hamster ovary cells to further elucidate the role of the membrane domain in enzyme degradation in response to physiological regulators. To accomplish this, we constructed sea urchin HMGal (uHMGal), the structural equivalent of hamster HMGal (httMGal), which has the sea urchin HMG-CoA reductase membrane domain fused to Escherichia coli beta-galactosidase. The uHMGal was stably expressed in CHO cells, and we found that the degradation of uHMGal is not accelerated by sterols, and even in the absence of sterols, it is less stable than hHMGal. We also constructed chimeric hamster/sea urchin HMGal molecules to investigate which amino acid sequences from the hamster enzyme are sufficient to confer sterol-regulated degradation upon the sea urchin enzyme. Our results identify the second membrane-spanning domain of hamster enzyme as important for the regulated degradation of HMG-CoA reductase.
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PMID:Molecular dissection of the role of the membrane domain in the regulated degradation of 3-hydroxy-3-methylglutaryl coenzyme A reductase. 764 76

The rate-limiting enzyme in cholesterol biosynthesis, 3-hydroxy-3-methylglutaryl-coenzyme A (HMG CoA) reductase, is regulated at a number of levels. One important mechanism is regulation of the half-life of the protein by a controlled proteolytic system. This comes about in response to downstream products of the sterol biosynthetic pathway. Little is known about this system, including where in the cell this regulated degradation occurs. HMG CoA reductase resides in the endoplasmic reticulum. To localize the site of regulated degradation of HMG CoA reductase, we used a construct that fuses the N-terminal membrane-anchoring domain of HMG CoA reductase in-frame with beta-galactosidase as a reporter domain (HM-Gal). HM-Gal has previously been shown to reproduce faithfully the degradative properties of native HMG CoA reductase (Chun et al. (1990) J. Biol. Chem. 265, 22004-22010). CHO cells transfected with DNA encoding HM-Gal were exposed to mevalonic acid, which enhances the rate of HMG CoA reductase degradation several fold, and leads to the reduction of the steady state levels of HM-Gal by 80-90%. To accumulate HMG CoA reductase at the site of degradation, cells were simultaneously treated with N-acetyl-leucyl-leucyl-norleucinal (ALLN), which inhibits the protease responsible for reductase degradation. HM-Gal was localized morphologically by immunofluorescence and biochemically by measuring beta-galactosidase activity in Percoll gradients of cellular homogenates. Using either technique HM-Gal localization was indistinguishable from that of ER markers in both control cells and in cells treated to accumulate HMG CoA reductase at the site of degradation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The regulated degradation of a 3-hydroxy-3-methylglutaryl-coenzyme A reductase reporter construct occurs in the endoplasmic reticulum. 784 77

Farnesyl acetate and ethyl farnesyl ether, two analogues of farnesyl pyrophosphate, stimulate post-transcriptional down-regulation of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, the rate-limiting enzyme in the biosynthesis of cholesterol and isoprenoids. Farnesyl acetate and ethyl farnesyl ether reduce translation of HMG-CoA reductase mRNA and enhance degradation of the enzyme, the same regulatory effects attributed to the putative non-sterol regulatory metabolite (Goldstein, J.L., and Brown, M.S. (1990) Nature 343, 425-430). HMGal, a fusion protein consisting of the membrane domain of HMG-CoA reductase linked to Escherichia coli beta-galactosidase, is subject to the same regulated degradation as HMG-CoA reductase (Skalnik, D. G., Narita, H., Kent, C., and Simoni, R. D. (1988) J. Biol. Chem. 263, 6836-6841). At 10 micrograms/ml (37.8 microM), farnesyl acetate and ethyl farnesyl ether trigger a 50-80% reduction in HMGal activity. Farnesyl acetate reduces the synthesis of HMG-CoA reductase and HM-Gal by 60-80%, but neither farnesyl compound affects HMG-CoA reductase mRNA levels. Farnesyl acetate and ethyl farnesyl ether stimulated the degradation of HMG-CoA reductase and HMGal, reducing the half-lives of the enzymes by 40-70%. In addition to their regulatory effects on HMG-CoA reductase, these farnesyl compounds also directly disrupt sterol synthesis.
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PMID:Non-sterol compounds that regulate cholesterogenesis. Analogues of farnesyl pyrophosphate reduce 3-hydroxy-3-methylglutaryl-coenzyme A reductase levels. 812 18

Transgenic mice carrying the 3-hydroxy-3-methylglutarylCoA reductase (HMG) promoter driving the Escherichia coli beta-galactosidase (lacZ) gene did not display the expected ubiquitous and constitutive expression in HMG-lacZ transgenic mice. The same promoter is however able to drive ubiquitous expression of the chloramphenicol acetyltransferase (cat) gene. Two lines of double HMG-lacZ and HMG-cat transgenic mice were obtained in which the two constructs were integrated at the same genomic sites. These mice expressed both reporter genes, but exclusively in the testes. These results suggest that the lacZ sequence might interfere negatively with the expression of the adjacent HMG-cat transgene.
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PMID:Cis effect of lacZ sequences in transgenic mice. 826 80

The Salmonella typhimurium phs chromosomal locus essential for the reduction of thiosulfate to hydrogen sulfide was cloned, and some features of its regulation were examined. The phs locus conferred H2S production on Escherichia coli, suggesting that it contains the structural gene for thiosulfate reductase. H2S production by the E. coli host was, as in S. typhimurium, suppressed by nitrate or glucose in the growth medium. The presence of plasmid-borne phs genes in a S. typhimurium chl+ host containing a chromosomal phs::lacZ operon fusion was found to significantly increase the relative induction efficiency of beta-galactosidase by thiosulfate. These results are consistent with a model for phs regulation in which the true inducer is not thiosulfate per se and in which the action of a phs-encoded molybdoprotein, possibly the reductase itself, converts thiosulfate into a compound that resembles the true inducer more closely than does thiosulfate.
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PMID:Cloning of the phs genetic locus from Salmonella typhimurium and a role for a phs product in its own induction. 840 12

A 3.6-kb EcoRI-SalI fragment of Paracoccus denitrificans DNA hybridized with a DNA probe carrying the poly(3-hydroxyalkanoate) (PHA) synthase gene (phaC) of Alcaligenes eutrophus. Nucleotide sequence analysis of this region showed the presence of a 1,872-bp open reading frame (ORF), which corresponded to a polypeptide with a molecular weight of 69,537. Upstream of the ORF, a promoter-like sequence was found. Escherichia coli carrying the fusion gene between lacZ and the ORF accumulated a level of poly(3-hydroxybutyrate) that was as much as 20 wt% of the cell dry weight in the presence of beta-ketothiolase and acetoacetylcoenzyme A reductase genes of A. eutrophus. The ORF was designated phaCPd. A plasmid vector carrying the phaCPd'-'lacZ fusion gene downstream of the promoter-like sequence expressed beta-galactosidase activity in P. denitrificans. When a multicopy and broad-host-range vector carrying the ORF along with the promoter-like sequence was introduced into P. denitrificans, the PHA content in the cells increased by twofold compared with cells carrying only a vector sequence.
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PMID:Molecular analysis of the poly(3-hydroxyalkanoate) synthase gene from a methylotrophic bacterium, Paracoccus denitrificans. 855 May 12

From Azospirillum lipoferum (Al) FS, a nitrogen-fixing bacterium isolated from the rhizosphere of rice, we cloned and sequenced draT, encoding dinitrogenase reductase ADP-ribosyltransferase, and draG, encoding dinitrogenase reductase-activating glycohydrolase. The nucleotide sequences of draTG showed extensive similarity to the same genes from Azospirillum brasilense, Rhodospirillum rubrum and Rhodobacter capsulatus, and they are assumed to be co-transcribed as a single operon. When this draTG operon was introduced into Klebsiella oxytoca, this organism acquired the ability to respond to extracellular NH(+4) ions with reversible inhibition of nitrogenase activity, similar to that seen in Al FS. We constructed a plasmid containing a draT::lacZ gene fusion and found that beta-galactosidase activity was detected under microaerobic conditions, regardless of NH(+4) concentration, but not under aerobic conditions. This indicates that the transcription of draTG responds to the level of oxygen, but not to that of NH(+4) ions.
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PMID:Cloning, sequencing and transcriptional regulation of the draT and draG genes of Azospirillum lipoferum FS. 862 Oct 68


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