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)

Five different carbon sources were examined for their ability to control synthesis of heat-stable enterotoxin (ST) by enterotoxigenic (ENT+) Escherichia coli grown in either a defined medium containing four amino acids or a minimal salts medium. No ST activity was observed when D-glucose, D-gluconate, and L-arabinose were added separately to the defined medium, whereas glycerol and pyruvate decreased toxin levels. Similar results were obtained using a minimal salts medium, except with pyruvate, which did not support growth. Inhibition of ST synthesis by D-glucose was overcome by the addition of 3 X 10(-3) M cyclic adenosine 3',5'-monophosphate. Glucose repression of beta-galactosidase synthesis under conditions optimal for inhibition of ST synthesis was also reversed by exogenous cyclic adenosine 3',5'-monophosphate in the presence of the inducer isopropyl-beta-D-thiogalactopyranoside. The data suggest that control mechanisms for the synthesis of plasmid gene products of bacterial pathogens are similar to those exerted on the host chromosome.
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PMID:Repression of heat-stable enterotoxin synthesis in enterotoxigenic Escherichia coli. 2 Apr 4

Antibodies bound to the surface of Escherichia coli cells stimulate the rate of growth of these bacteria in proportion to their quantity. This "cytostimulation" of the bacteria is confirmed by (1) the increase in optical density, (2) colony counts and (3) increase in the beta-galactosidase activity of a constitutive strain. This action can be amplified by overlaying the antibodies bound to the bacteria, with anti-antibodies. The cytostimulation is accompanied by an increase of the ratio in phosphatidylglycerol to diphosphatidyl-glycerol in the bacteria.
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PMID:[Bacterial cytostimulation by specific antibodies (author's transl)]. 5 Jul 58

Fruiting body formation in the bacterium Myxococcus xanthus consists of a temporal sequence of cellular aggregation and sporulation. During the period of cellular aggregation, a major new development-specific protein that has lectin-like activity is synthesized. This protein, called myxobacterial hemagglutinin (MBHA), was able to agglutinate sheep or guinea pig erythrocytes but not horse, ox, chicken, or human erythrocytes. MBHA was undetectable in extracts of vegetative cells, cells starved in liquid buffer, or in glycerol-induced cells. However, cells starved on a fruiting medium produced large amounts of MBHA (about 5% of protein synthesis), starting at about 6-8 hr of development. The protein accumulated in the soluble fraction of cells, reaching a peak of 1-2% of total protein at about the time when aggregation was completed. At later times the amount of MBHA present in the soluble fraction declined although synthesis continued. The hemagglutinating activity of MBHA could not be inhibited with simple sugars or aminosugars but could be inhibited with fetuin, a fetal calf serum glycoprotein. The O-glycosidically linked trisaccharide glycopeptide of fetuin was shown to be inhibitory by itself. The penultimate galactose of this glycopeptide was directly implicated in the inhibitory activity, because the inhibition by asialofetuin was reduced to 1/60th by periodate oxidation and to 1/15th after beta-galactosidase treatment. MBHA is an abundant biochemical marker of development in M. xanthus. The fact that it is a lectin suggests that it may play a role in cell-cell recognition or agglutination.
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PMID:Myxobacterial hemagglutinin: a development-specific lectin of Myxococcus xanthus. 9 78

Synthesis of beta-galactosidase by Streptomyces violaceus was induced by D-galactose and L-arabinose, and to a lesser extent by lactose, D-arabinose, and methyl-beta-D-galactopyranoside. The synthesis of the enzyme was linear and started to increase 2--3 h after induction by galactose, reaching a maximum after 5--7 h. The highest level of specific activity was observed in 2% galactose, with an increase of 45 times over the basal level in glycerol. Isopropyl-beta-D-thiogalactopyranoside (IPTG) and methyl-beta-D-thiogalactopyranoside (TMG) inhibited induction by D-galactose, but did not influence enzymatic activity. Cellular extracts hydrolyzed O-nitrophenyl-beta-D-galactopyranoside, but did not significantly hydrolyze lactose, melibiose, p-nitrophenyl-alpha-D-galactopyranoside, p-nitrophenyl-beta-D-fucoside, or p-nitrophenyl-beta-D-glucopyranoside. Rifampicin and chloramphenicol inhibited beta-galactosidase synthesis in non-preinduced and in preinduced cells. The inhibition by chloramphenicol was reversible.
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PMID:Induction of beta-galactosidase in Streptomyces violaceus. 11 72

The rates of synthesis of beta-galactosidase (EC 3.2.1.23) and the intracellular levels of cyclic 3',5'-adenosine monophosphate (cAMP) soon after the addition of glucose or glycerol to exponentially growing cultures of Escherichia coli have been determined. Within 10 s of its addition, glucose, but not glycerol, lowered the apparent initiation frequency of lac messenger ribonucleic acid. The glucose-generated reduction in initiations is identified as catabolite repression by its reversibility with cAMP. The intracellular cAMP levels respond virtually identically to glucose and glycerol additions. Thus, no correlation was observed between the rate of messenger ribonucleic acid initiation and the level of cAMP.
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PMID:Kinetics of the onset of catabolite repression in Escherichia coli as determined by lac messenger ribonucleic acid initiations and intracellular cyclic adenosine 3',5'-monophosphate levels. 16 31

The relationship between cyclic adenosine 3',5'-monophosphate (cyclic AMP) metabolism and the induction of tryptophanase and beta-galactosidase was studied in several strains of Escherichia coli grown with succinate, acetate, glycerol, or glucose as the carbon source. No consistent relationship between the intracellular concentration of cyclic AMP in the several strains cultured and the various carbon sources was discerned. In E. coli K-12-1 the induction of tryptophanase was found to vary in the order: succinate greater than acetate greater than glycerol greater than glucose, and that of beta-galactosidase was found in the order: glycerol greater than acetate greater than succinate greater than glucose. Rate of accumulation of cyclic AMP in the culture filtrate was in the order: succinate greater than acetate greater than glycerol greater than glucose. The addition of glycerol to E. coli K-12-1 grown in acetate caused inhibition of tryptophanase and slight inhibition of accumulation of extracellular cyclic AMP. These same conditions caused beta-galactosidase induction to be stimulated. The addition of exogenous cyclic AMP to cultures grown with four different carbon sources had an effect characteristic for each of the two enzymes studied as well as each individual carbon source. The results suggest that there are control elements distinct from cyclic AMP and its receptor protein which respond to the catabolic situation of the cell.
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PMID:Metabolism of cyclic adenosine 3',5'-monophosphate and induction of tryptophanase in Escherichia coli. 17 Feb 48

The synthesis of beta-galactosidase by an E. coli constitutive mutant was examined in a chemostat using glucose-, glycerol-, succinate- or N-limited growth media. Except for glucose-grown bacteria, the steady-state intracellular level of beta-galactosidase was maximal at dilution rates between 0-2 and 0-3 h-1. At higher dilution rates enzyme synthesis was reduced by catabolite repression, which could be relieved by the addition of cyclic AMP. With a catabolite-resistant mutant (UV5c), no decrease in enzyme level at high dilution rates were observed. All mutants examined were constitutive and gave decreased enzyme levels at low dilution rates, with the exception of lac-/F'lac UV5c mutants where the enzyme levels rose at low dilution rates. Hyper-producing mutants were isolated but were unstable. A constitutive mutant growing on glycerol-limited media was considered the most suitable for large-scale production of beta-galactosidase in a chemostat.
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PMID:The synthesis of beta-galactosidase by constitutive and other regulatory mutants of Escherichia coli in chemostat culture. 17 Mar 62

Two mutants are described in which the synthesis of tryptophanase is unusually insensitive to catabolite repression. Neither mutation is linked by transduction to the tryptophane structural gene, neither mutation renders the synthesis of beta-galactosidase insensitive to catabolite repression, and the mutations do not permit tryptophanase to be synthesized in strains deficient in adenyl cyclase. During growth in glucose-minimal medium the mutants maintained a similar intracellular concentration of cyclic AMP to their wild-type parent; but since in the wild type the concentration of cyclic AMP was the same in glycerol-minimal medium as in glucose-minimal medium, it is doubtful whether catabolite repression is mediated by measurable changes in the concentration of this nucleotide.
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PMID:Mutations in Escherichia coli that relieve catabolite repression of tryptophanase synthesis. Mutations distant from the tryptophanase gene. 17 93

Three temperature-sensitive mutant strains for RNA polymerase beta or beta' subunits (carrying mutations tsx, A2R7 and R120) were used in order to investigate the dependence of the induced lac expression on stimulation by cyclic AMP after the shift to non-permissive temperature. High temperature lowered the rate of beta-galactosidase synthesis. However, the low rate of synthesis could be strongly increased by cyclic AMP (30, 2.4 and 5.7-fold increases for tsX, A2R7 and R120 mutants, respectively). At the permissive temperature stimulation by cyclic AMP was less than 1.4-fold (minimal medium supplemented with glycerol). The results suggest that the maximal expression of the lac operon is saturated, that is, a hypothetical increase in RNA polymerase or cAMP-CRP concentration in the cell with not enhance the expression. The concept of saturation explains why it was possible to increase the beta-galactosidase synthesis in conditions of limited promoter binding activity of RNA polymerase through increase in concentration of cyclic AMP-CRP complex in the cell (addition of cyclic AMP) to the values higher than that observed on glycerol.
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PMID:Expression of the lac operon in RNA polymerase mutants of Escherichia coli K12. 22 41

Mutants altered in carbon catabolite regulation have been isolated by selecting for mutants of the areA217 strain capable of using acetamide as the sole nitrogen source in the presence of sucrose. In addition to creA mutants described previously be Arst and Cove, strains with mutations in two new genes, creB and cre C, have been found. The creB and creC mutants grow poorly on some sole carbon sources and have low levels of some enzymes of carbon catabolism e.g. beta-galactosidase and D-quinate dehydrogenase. The creB and creC mutants are hypersensitive to fluoroacetate, fluoroacetamide and allyl alcohol in the presence of glucose or sucrose but not glycerol; and the enzymes, acetamidase and alcohol dehydrogenase, are less sensitive to carbon catabolite repression than the wild-type strain. Extracellular protease and alpha-glucosidase enzyme activities are elevated in creB and creC mutants, while L-proline and L-glutamate uptake capacities are lower in both the presence and absence of glucose. Interactions between creA, B and C mutations have been investigated in double mutants, and the dominance properties of creB and creC mutants determined. The results indicate that the creB and creC genes may have a regulatory role in the control of carbon catabolism.
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PMID:Pleiotropic mutants of Aspergillus nidulans altered in carbon metabolism. 32 Apr 55


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