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)

Tetrathionate reduction can be detected simply by acid production. Some commonly occuring Salmonella serotypes can be subdivided into biotypes by the tetrathionate reductase test. The enzyme beta-glucuronidase can be detected using p-nitro-phenyl-beta-D-glucuronide as substrate. The enzyme was found in 30% of Salmonella strains. Each Salmonella serotype was found homogeneous with respect to presence of (or lack of) beta-glucuronidase. This test can then be useful for the identification of monophasic or non-motile variants of normally diphasic serotypes. A positive ONPG-test does not always indicate the presence of a true beta-galactosidase. In the genus Salmonella, ONPG-positive strains of sub-genus III and strains harboring a lactose-plasmid have a true beta-galactosidase. A late positive ONPG-test - as commonly shown by subgenus II strains - is not due to a true beta-galactosidase. The distinction between beta-galactosidase positive and beta-galactosidase negative strains among ONPG-positive strains may be taxonomically significant.
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PMID:[Tetrathionate reductase, beta-glucuronidase, and ONPG-test in the genus Salmonella (author's transl)]. 45 69

The distribution of acid phosphatase, beta-N-acetylglucosaminidase, beta-glucuronidase, and acid beta-galactosidase was studied in mm. extensor digitorum longus, soleus, and diaphragm of rats. Using the technic of semipermeable membranes activities of these enzymes were demonstrated beside cells of the interstitial tissue in muscle fibers themselves as well. Acid phosphatase displayed the highest activity which appeared in many small dots dispersed in the fiber. The activity of acid phosphatase was about 1.2 X higher in the m. soleus than in the m. extensor digitorum longus. In the latter muscle a somewhat higher activity was often found in muscle fibers displaying a higher staining for NADH tetrazolium reductase. The activity of beta-N-acetylglucosaminidase was slightly lower, that of beta-glucuronidase very weak but still discernible. The activity of acid beta-galactosidase was not ascertained in the majority of fibers. The ratio of activities measured in an area of the same size in cells of the interstitial tissue and in muscle fibers amounted in average to 2.6:1 in the case of acid phosphatase, 2.5:1 in the case of beta-N-acetylglucosaminidase, 5.7:1 in the case of beta-glucuronidase, and 44.3:1 in the case of acid beta-galactosidase. The importance of the histochemical technic in studies concerned with acid hydrolases in striated muscle fibers in normal and pathological conditions is pointed out.
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PMID:Histochemistry of some acid hydrolases in striated muscles of the rat. 99 74

Human gallbladder epithelium was homogenized with a view to maintaining the integrity of subcellular components. In such homogenates, N-acetyl-beta-glucosaminidase, beta-glucuronidase, beta-galactosidase, beta-glucosidase, beta-fucosidase, beta-xylosidase, and acid phosphatase were demonstrated together with phospholipase activity. All the enzymes exhibited structure-linked latency. After discarding cellular debris from the homogenate, remaining subcellular organelles were analytically separated by density gradient centrifugation. After 100,000 g for 1 hour, particles containing acid glycosidases were recovered at a sucrose density of 1.18-1.19, whereas the mitochondrial marker enzyme succinate-reductase accumulated at a density of 1.16. The bulk of sedimentable phospholipase activity was recovered with particles sedimenting at 1.18-1.19. The results are interpreted as indicating that phosphalipase is present in lysosomes of the human gallbladder epithelium. Release of acid hydrolases, in lysosomes of the human gallbladder epithelium. Release of acid hydrolases, in lysosomes of the human gallbladder epithelium. Release of acid hydrolases, particularly phospholipase A, from the gallbladder epithelium is discussed as mediation of an inflammatory reaction in the gallbladder, i.e. cholecystitis.
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PMID:On the mediation inflammatory reaction in the human gallbladder epithelium. 127 7

Gastric mucosal PG E2 receptors are the common antisecretory working point of all prostanoid types and may also be involved in "protective" effects. We investigated the subcellular localization of these receptors, as measured by displaceable 3H-PG E2 binding, and identified different organelles by monitoring the activities of specific marker enzymes. Porcine mucosal homogenates were subdivided by differential centrifugation into fractions P1 (1000 x g), P2 (20,000 x g), P3 (300,000 x g) and the supernatant S1. P3 was further fractionated over a series of sucrose step gradients. Mitochondria and lysosomes were enriched in P2 (maximum specific activities of cytochrome-c-oxidase of beta-glucosidase, beta-glucuronidase, beta-galactosidase, respectively). Plasma membranes (alkaline phosphatase, gamma-glutamyl-transpeptidase, 5-nucleotidase), tubulovesicles (H+/K(+)-ATPase) and rough endoplasmic reticulum (NADPH-cytochrome-c-reductase) were mainly found in P3, which also contained the majority of 3H-PG E2 binding sites. In contrast, prostanoid binding was barely detectable in S1. Density fractionation of P3 revealed that 3H-PG E2 binding sites shared a similar sedimentation profile with plasma membranes and tubulovesicular markers. No or negative correlation was found with lysosomes, rough endoplasmic reticulum and mitochondria. We conclude that mucosal PG E2 receptors are predominantly located at the cell surface. This supports the view that prostanoids inhibit gastric secretion through membrane receptors, but gives no clue for intracellular "protective" working points.
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PMID:Subcellular localization of prostaglandin E2 receptors in the gastric mucosa. 134 83

We have raised two monospecific antibodies against synthetic peptides derived from the membrane domain of the ER glycoprotein 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the rate limiting enzyme in the cholesterol biosynthetic pathway. This domain, which was proposed to span the ER membrane seven times (Liscum, L., J. Finer-Moore, R. M. Stroud, K. L. Luskey, M. S. Brown, and J. L. Goldstein. 1985. J. Biol. Chem. 260:522-538), plays a critical role in the regulated degradation of the enzyme in the ER in response to sterols. The antibodies stain the ER of cells and immunoprecipitate HMG-CoA reductase and HMGal, a chimeric protein composed of the membrane domain of the reductase fused to Escherichia coli beta-galactosidase, the degradation of which is also accelerated by sterols. We show that the sequence Arg224 through Leu242 of HMG-CoA reductase (peptide G) faces the cytoplasm both in cultured cells and in rat liver, whereas the sequence Thr284 through Glu302 (peptide H) faces the lumen of the ER. This indicates that a sequence between peptide G and peptide H spans the membrane of the ER. Moreover, by epitope tagging with peptide H, we show that the loop segment connecting membrane spans 3 and 4 is sequestered in the lumen of the ER. These results demonstrate that the membrane domain of HMG-CoA reductase spans the ER eight times and are inconsistent with the seven membrane spans topological model. The approximate boundaries of the proposed additional transmembrane segment are between Lys248 and Asp276. Replacement of this 7th span in HMGal with the first transmembrane helix of bacteriorhodopsin abolishes the sterol-enhanced degradation of the protein, indicating its role in the regulated turnover of HMG-CoA reductase within the endoplasmic reticulum.
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PMID:Immunological evidence for eight spans in the membrane domain of 3-hydroxy-3-methylglutaryl coenzyme A reductase: implications for enzyme degradation in the endoplasmic reticulum. 137 17

A sensitive umu test system for the detection of mutagenic nitroarenes has been developed using a new tester strain Salmonella typhimurium NM1011 having a high nitroreductase activity. The new strain was constructed by subcloning the bacterial nitroreductase gene into a plasmid pACYC184 and introducing the plasmid into the original strain S. typhimurium TA1535/pSK1002 harboring a fusion gene umuC'-'lacZ (pSK1002). Thus, the tester strain enabled us to monitor the genotoxic activities of various nitroarene compounds by measuring the beta-galactosidase activity in the cells. The sensitivity of strain NM1011 was compared with that of the parent tester strain S. typhimurium TA1535/pSK1002 or a nitroreductase-deficient strain S. typhimurium NM1000 with respect to the induction of umuC gene expression by 17 mutagenic nitroarenes. The newly developed strain with high nitroreductase activity had about 3 times higher nitrofurazone-reductase activity than the parent strain and was highly sensitive to the compounds 2-nitrofluorene, 1-nitronaphthalene, 2-nitronaphthalene, 1-nitropyrene, m-dinitrobenzene, 4,4'-dinitrobiphenyl, 3-nitrofluoranthene, 3,7-dinitrofluoranthene, 3,9-dinitrofluoranthene, 5-nitroacenaphthene and 2,4-dinitrotoluene. By contrast, the enzyme-deficient strain did not show any considerable response to 2-nitrofluorene, m-dinitrobenzene, 1-nitronaphthalene, 2-nitronaphthalene, 1-nitropyrene, 4,4'-dinitrobiphenyl, 3-nitrofluoranthene, 3,7-dinitrofluoranthene, 2,4-dinitrotoluene and 5-nitroacenaphthene. These results suggest that the newly developed tester strain with high nitroreductase activity is very useful for the detection of potent mutagenic nitroarene compounds.
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PMID:A sensitive umu test system for the detection of mutagenic nitroarenes in Salmonella typhimurium NM1011 having a high nitroreductase activity. 138 53

Squalene synthase (farnesyldiphosphate:farnesyldiphosphate farnesyltransferase, EC 2.5.1.21) converts farnesyl pyrophosphate to squalene, the first metabolic step committed solely to the biosynthesis of sterols. Using a fluorescence-activated cell sorting technique designed to screen for cells defective in the regulated degradation of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, we isolated a squalene synthase-deficient mutant of Chinese hamster ovary cells. The mutant cell line, designated SSD, exhibits less than 7% of the squalene synthase activity of the parental cell line, CHO-HMGal. Both the SSD and the parental cells stably express HMGal, a model protein for studying the regulated degradation of HMG-CoA reductase, which consists of the membrane domain of HMG-CoA reductase fused to bacterial beta-galactosidase (Skalnik, D. G., Narita, H., Kent, C., and Simoni, R. D. (1988) J. Biol. Chem. 263, 6836-6841). In this study, the regulatory effects of mevalonate and compactin on the activity levels of HMGal are substantially reduced in SSD cells as compared to the parental cell line. In lipid-poor medium, SSD cell growth is arrested. The rate of [3H]acetate incorporation into cholesterol for the mutant SSD cells is less than 2% of the rate for the parental cells. However, the incorporation of [3H] squalene into sterols is essentially wild type for SSD cells. When the mutant SSD cells are fed [3H]acetate, radioactivity accumulates in farnesol, much of which is secreted into the medium. By growing SSD cells in lipid-poor medium, a revertant cell type, designated SSR, was isolated. In every assay performed the revertant SSR cells exhibited a phenotype that was essentially wild type, demonstrating that the SSD mutant phenotype was the result of a single mutation.
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PMID:Squalene synthase-deficient mutant of Chinese hamster ovary cells. 152 71

The principal iron uptake system of Saccharomyces cerevisiae utilizes a reductase activity that acts on ferric iron chelates external to the cell. The FRE1 gene product is required for this activity. The deduced amino acid sequence of the FRE1 protein exhibits hydrophobic regions compatible with transmembrane domains and has significant similarity to the sequence of the plasma membrane cytochrome b558 (the X-CGD protein), a critical component of a human phagocyte oxidoreductase, suggesting that FRE1 is a structural component of the yeast ferric reductase. FRE1 mRNA levels are repressed by iron. Fusion of 977 base pairs of FRE1 DNA upstream from the translation start site of an Escherichia coli lacZ reporter gene confers iron-dependent regulation on expression of beta-galactosidase in yeast. An 85-base-pair segment of FRE1 5' noncoding sequence contains a RAP1 binding site and a repeated sequence, TTTTTGCTCAYC; this segment is sufficient to confer iron-repressible transcriptional activity on heterologous downstream promoter elements.
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PMID:Ferric reductase of Saccharomyces cerevisiae: molecular characterization, role in iron uptake, and transcriptional control by iron. 157 Mar 6

We have studied the regulated degradation of the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase within the endoplasmic reticulum in cells permeabilized with digitonin. Using Chinese hamster ovary cells transfected with a plasmid encoding HMGal, a chimeric protein containing the membrane domain of HMG-CoA reductase coupled to beta-galactosidase, we have demonstrated mevalonate and sterol-stimulated loss of beta-galactosidase activity. In pulse-chase experiments we have demonstrated mevalonate-stimulated degradation of both HMGal and HMG-CoA reductase. The rate of mevalonate-stimulated degradation observed in permeabilized cells tends to be slightly slower than that observed in intact cells treated with mevalonate and is dependent upon incubation of cells with mevalonate prior to permeabilization. The degradation process measured in this report extends a previous report of HMG-CoA reductase degradation in digitonin-permeabilized cells (Leonard, D. A., and Chen, H. W. (1987) J. Biol. Chem. 262, 7914-7919) by mimicking key physiological features of the in vivo process, including: stimulation by regulatory molecules, specifically mevalonate and sterols; inhibition by cycloheximide; and inhibition by an inhibitor of neutral cysteine proteases.
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PMID:Regulated degradation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase in permeabilized cells. 161 56

We have constructed a series of mutations in the membrane and linker domains of Syrian hamster 3-hydroxy-3-methylglutaryl-(HMG) CoA reductase in order to determine the regions critical for the regulated degradation of the enzyme. In transfected Chinese hamster ovary cells, we have expressed a fusion protein, HMGal, which consists of the membrane and linker domains of the Syrian hamster HMG-CoA reductase fused to beta-galactosidase. Using this fusion protein, we have determined that a deletion of 64 amino acids from the central region of the membrane domain causes the protein to be degraded extremely rapidly. In addition, deletion of PEST sequences has little effect on degradation, but deletion of the linker domain makes the protein's degradation insensitive to sterols and mevalonate. In addition to deletion mutations, we have systematically replaced each hydrophobic, putative membrane spanning region of the membrane domain with the first transmembrane sequence from bacteriorhodopsin. Replacement of span 4 has no effect on degradation. Replacements of spans 5 or 6 result in a protein which has a normal basal rate of degradation, but this rate of degradation is not accelerated by mevalonate, low density lipoprotein, or 25-hydroxycholesterol. Replacement of span 3 results in a protein whose degradation is similarly not accelerated by sterols or mevalonate, but since this protein might be mislocalized, these results are inconclusive. Replacement of span 7 yields a short-lived protein which is degraded more rapidly in response to mevalonate but not in response to exogenous sterols. Replacement of span 8 extends both the basal and mevalonate-accelerated half-life about 5-fold. This work begins to define the critical regions for regulated degradation within the membrane domain of HMG-CoA reductase.
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PMID:The role of the membrane domain in the regulated degradation of 3-hydroxy-3-methylglutaryl coenzyme A reductase. 174 Apr 63


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