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

---

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

cAMP acts as a primary signal and is regulated by a secreted cyclic nucleotide phosphodiesterase (PDE) throughout development in Dictyostelium discoideum. Expression of the PDE gene (pde) is controlled by promoters specific to vegetative growth (prV), aggregation (prA), or late development (prL). Promoter-containing regions were individually fused to the pde coding sequence. After transformation multiple copies of each construct led to overexpression of PDE mRNA and enzyme activity with the temporal profile expected of each promoter. Overexpression of PDE from prV and prA altered the timing of aggregation compared to control transformants, but the final morphology was normal. Control transformants showed delayed aggregation compared to nontransformed cells. Cells that overexpressed PDE from prL aggregated like the control transformants, but no fruiting bodies were formed. Individual promoter regions were fused to the beta-galactosidase gene (lacZ). Cells that expressed prA-lacZ were dispersed throughout aggregation fields and mounds. Cells that expressed prL-lacZ were first seen distributed homogeneously throughout tight and tipped mounds. In slugs most of these cells are localized in the anterior region. During culmination, cells that expressed the prL-lacZ construct became incorporated into the stalk and were seen in the upper and lower cups surrounding the spore mass.
...
PMID:The role of the cyclic nucleotide phosphodiesterase of Dictyostelium discoideum during growth, aggregation, and morphogenesis: overexpression and localization studies with the separate promoters of the pde. 838 36

Actinomyces viscosus T14V, a Gram-positive bacterium found in the oral cavity, was found to be insensitive to glucose-mediated catabolite repression. Basal levels of beta-galactosidase (18-26 U) were observed at all phases of growth regardless of the culture conditions. Further, beta-galactosidase could not be induced with lactose, or with a known inducer of the enzyme, isopropyl-beta-D-thiogalactoside, or with dibutyryl cAMP. Glucose, on the other hand, stimulated cAMP accumulation in a concentration-dependent manner. Fructose and sucrose mimicked the effects of glucose on cAMP accumulation, whereas galactose, mannose and maltose had lesser stimulatory effects. Other carbon sources, i.e., lactose, alpha-methylglucoside, ribose, xylose and succinate were without effect. Glucose and alpha-methylglucoside were found to stimulate cAMP accumulation in toluene-permeabilized cells, in the presence of the phosphodiesterase inhibitor, theophylline. Glucose did not stimulate cAMP levels in other Gram-positive bacteria including Streptococcus mutans, S. sanguis and S. salivarius but did cause cAMP accumulation in other strains of A. viscosus. The results suggest that glucose effects on cAMP metabolism are independent of the induction of beta-galactosidase as presently defined for Escherichia coli, and that the effects appear to be selective to the A. viscosus bacteria. The results also suggest that glucose stimulates cAMP accumulation via activation of adenylate cyclase.
...
PMID:Glucose stimulates cAMP accumulation in the oral bacterium Actinomyces viscosus. 839 89

Signal transduction via a family of cAMP receptor subtypes (cARs) is critical for proper development in the cellular slime mold Dictyostelium. Genes encoding four related subtypes have been cloned and their expression, based on RNA accumulation, has been previously reported. Here we report the differential spatial and temporal distribution of cAR2 and cAR3 proteins, based on indirect double immunofluorescence. Cells were transformed with a carB::lacZ construct, and an antibody against beta-galactosidase was used to visualize cAR2 expression. Simultaneously, a cAR3-specific antibody was used to identify cAR3-expressing cells. Results indicate that by the time of tip formation (12-14 hr) both receptors are expressed and distribute in a virtually nonoverlapping pattern, with cAR2 being expressed on anterior, prestalk cells and cAR3 present in the rest of the organism. Differential distribution of these two receptor subtypes may result in distinct cAMP signaling mechanisms in the two major regions of the organism.
...
PMID:Differential distribution of cAMP receptors cAR2 and cAR3 during Dictyostelium development. 857 36

Thermotoga neapolitana is a hyperthermophilic bacterium whose phylogenetic lineage includes the most primitive of the bacterial heterotrophs. It is not known whether Thermotoga exhibits preferences for growth substrates or regulates the synthesis of degradative enzymes. We have found that T. neapolitana exhibits diauxic growth in medium containing 300 microM glucose and 1 mM lactose. We measured the activity of beta-galactosidase and beta-glucosidase in extracts prepared from cells grown on defined media and found that cells grown on 0.5% lactose, galactose or cellobiose contained beta-galactosidase specific activities of 1.19, 1.78 and 1.34 U (mg protein)-1, respectively. Cells grown on 0.5% glucose, maltose, fructose, sucrose, xylose, ribose or starch had no measurable beta-galactosidase activity. beta-Glucosidase activity was found only in cells grown on cellobiose. Cells grown on the combination of 0.5% lactose or galactose and 0.05% glucose had no detectable beta-galactosidase activity, whereas up to 0.5% glucose did not prevent expression of beta-galactosidase or beta-glucosidase activity in cells induced with 0.5% cellobiose. These activities are catalysed by separate enzymes as determined by resolution of their activities on 6% native polyacrylamide gels. Therefore, only beta-galactosidase synthesis induced by lactose is subject to catabolite repression. To determine the mechanism of catabolite repression, the levels of cAMP were measured in T. neapolitana cells grown on various defined media using an enzyme-immunoassay. The cAMP levels ranged from 44 to 280 fmol (mg protein)-1 irrespective of the carbon source used. By comparison, Escherichia coli grown on lactose contained 5.1 pmol (mg protein)-1. Like Gram-positive bacteria, T. neapolitana displays a cAMP-independent mechanism for catabolite repression and this may represent the more ancient mode of regulation.
...
PMID:Catabolite repression in the hyperthermophilic bacterium Thermotoga neapolitana is independent of cAMP. 858 Nov 60

Dictyostelium discoidium cells express a family of cell surface cAMP receptors, and these G-protein-coupled receptors are each expressed with unique spatial and temporal patterns. One of these receptors, cAR2, is present during the postaggregative stages of development and our previous work suggests that it is preferentially expressed in prestalk cells. We report here the isolation of the promoter for carB, the gene which encodes cAR2. Using this fragment to generate a carB::lacZ, gene fusion construct, we investigated carB expression in detail. Expression is first detected at the tight aggregate stage and subsequently in a pattern reminiscent of the prestalk-specific gene ecmA. There are subtle differences, however, with, ecmA being expressed significantly in the anterior-like cells of the migrating pseudoplasmodium and in the basal disc and lower cup supporting the sorus during terminal development. carB is not expressed in any of these places. The presence of these different prestalk cell subtypes was confirmed by double indirect immunofluorescence using anti-cAR2 and anti-beta-galactosidase antibodies. While virtually all cAR2-expressing cells also express ecmA::lacZ, a substantial fraction of ecmA::lacZ-positive cells do not express cAR2. We also found the regulation of carB gene expression to differ from that of ecmA. carB expression is induced in vitro by extracellular cAMP, but surprisingly, not by DIF-1, a soluble molecule thought to be essential for the initiation of prestalk differentiation. Thus, cAR2 appears to be a cAMP receptor present on a restricted subset of prestalk cells and whose expression does not respond typically to the prestalk inducer DIF-1. DIF-1 sensitivity may, therefore, not be characteristic of all early prestalk differentiation.
...
PMID:The cAMP receptor subtype cAR2 is restricted to a subset of prestalk cells during Dictyostelium development and displays unexpected DIF-1 responsiveness. 863 93

Adrenergic responses of rat hepatocytes were studied by measuring Ins(1,4,5)P3(for the response via alpha 1-subtype receptors) and cAMP (for beta-subtype response) generation during brief incubation of cells with respective agonists. Hepatocytes from young rats with an age of 1 week displayed a very high beta response without a significant alpha 1 response. The beta response decreased and the alpha 1 response increased progressively as the age increased; the response was almost exclusively via alpha 1 receptors in hepatocytes of adult rats 9 weeks or more old. The beta response developed, again at the expense of the alpha 1 response, in hepatocytes from adult rats during the primary culture at low cell densities [(1-2.5) x 10(4) cells/cm2]. Such "alpha 1 to beta subtype switching' of adrenergic responses in vitro was totally inhibited by adding plasma membranes prepared from adult rat liver into the low-cell-density culture, but not inhibited at all by membranes from young rat liver. The inhibitory effect of adult rat liver membranes was lost when the membranes had been exposed to endoglycosidase F or beta-galactosidase but was not affected by prior treatment with sialidase. On the contrary, young rat liver membranes became inhibitory to "alpha 1 to beta subtype switching' after prior treatment with sialidase. Thus glycoproteins with unsialylated galactosyl termini on the surface of adult rat hepatocytes are likely to function as a determinant of the relative development of alpha 1/beta subtypes of adrenergic responses; the beta response is predominant in hepatocytes in the juvenile, presumably as a result of sialylation of the galactosyl termini of the functional glycoproteins.
...
PMID:A role of asialoglycoproteins for plasma-membrane-induced inhibition of the switching from alpha 1 to beta subtypes in adrenergic response during primary culture of rat hepatocytes. 867 Jan 47

Escherichia coli shifted from external pH (pH(O)) 7.0 to pH(O) 8.5-9.5 rapidly becomes tolerant to pH(O) 10.0-11.5, induction of tolerance (alkali habituation) being dependent on periplasmic or external alkalinization with either NaOH or KOH. Induction needs protein synthesis and makes organisms resistant to DNA damage by alkali and better able to repair any damage that occurs. Induction of tolerance was reduced by glucose (not reversed by cAMP) and by amiloride, was dependent on DNA gyrase and was abolished by fur and himA lesions (the latter suggests IHF involvement). Tolerance induction was not prevented by L-leucine, FeCl3 or FeSO4 nor by hns or relA mutations. Habituation probably involves attachment of IHF upstream of the promoter leading to DNA bending which switches on transcription. Habituation is aberrant in nhaA mutants, so ability to resist alkali damage may only arise if NhaA is induced, with extrusion of Na+ by this antiporter during alkali challenge. In accord with one tolerance component involving NhaA induction, beta-galactosidase formation from nhaA-lacZ fusions at pH(O) 9.0 was inhibited by glucose and amiloride.
...
PMID:Regulatory aspects of alkali tolerance induction in Escherichia coli. 869 68

Transcriptional regulation of the rhaT gene, one of the operons forming the rhamnose regulon in Escherichia coli, was studied by fusing its complete or deleted promoter to the reporter gene lacZ. Analysis of beta-galactosidase activities induced in these constructions grown under different conditions predicted the presence of two putative control elements: one for the RhaS regulatory protein and activating the gene not only by L-rhamnose but also by L-lyxose or L-mannose, the other for cAMP-catabolite repression protein and activating this gene in the absence of glucose. Anaerobiosis increased the promoter function two- to threefold with respect to the aerobic condition. Experiments involving complementation of strains containing the rhaT-promoter fusion and carrying a deletion in the rhaS and/or rhaR genes with plasmids bearing the rhamnose regulatory genes showed that rhaT is controlled by a regulatory cascade, in which RhaR induces rhaSR and the accumulated RhaS directly activates rhaT.
...
PMID:Transcriptional regulation of the Escherichia coli rhaT gene. 875 46

We have identified a gene, cpdA, located at 66.2 min of the chromosome of Escherichia coli that encodes cyclic 3',5'-adenosine monophosphate phosphodiesterase (cAMP phosphodiesterase, EC). The expression of beta-galactosidase, which is a product of the lacZ gene, was repressed in cells that harbored multiple copies of the plasmid carrying the cpdA gene. Northern blotting showed that the transcription of the lacZ gene was inhibited in these cells. Multiple copies of the cpdA gene decreased the intracellular concentration of cAMP, which is a positive regulator for transcription of the lacZ gene. We found that the purified CpdA protein repressed in vitro transcription from the lacP1 promoter by decreasing cAMP. In addition, we showed that the CpdA protein hydrolyzed cAMP to 5'-adenosine monophosphate and that its activity was activated by iron. Our results suggested that regulation of intracellular concentration of cAMP is dependent not only on synthesis of cAMP but also on hydrolysis of cAMP by cAMP phosphodiesterase.
...
PMID:Identification of the cpdA gene encoding cyclic 3',5'-adenosine monophosphate phosphodiesterase in Escherichia coli. 881 Mar 11

The fibronectin (FN) gene is under complex regulatory control in vitro and in vivo. Sequences from the rat FN gene directed efficient expression of a lacZ reporter gene product, beta-galactosidase, in NIH/3T3 mouse fibroblasts. Stable transfectants were generated to facilitate studies of gene regulation by cell growth state. The expression of FN-lacZ constructs increased approximately twofold when cultures attained confluence, relative to total protein. The magnitude of this increase correlates well with that observed for FN mRNA levels and protein synthesis rate. Fragments containing 4.9, 0.9, or 0.3 kbp upstream of the transcription start site are equally responsive to cell density and/or cell contact. Deletion of a cAMP-responsive element enhanced the response, suggesting a negative role for this sequence motif and demonstrating that the FN gene is regulated by cell density at the transcriptional level. The effect of high cell density is apparently different from decreased growth rate, as incubation with low serum did not result in increased expression of the lacZ reporter. Finally, conditioned medium from dense cells did not enhance reporter gene expression in sparse cells, suggesting that the density signal is not transmitted via a soluble factor.
...
PMID:Modulation of transcription of the rat fibronectin gene by cell density. 889 5


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---