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 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

The mechanism of the interference of the antiviral antibiotic distamycin A with the bacterial cell has been investigated. Labelled distamycin A is firmly bound by E. coli cells and the binding process does not require metabolic energy as indicated by the use of inhibitors. The antibiotic does not induce gross alteration in the cell membrane but inhibits cyclic AMP accumulation in the cells exposed to a glucose-free medium. This inhibition is concomitant with that exerted on the synthesis of an inducible enzyme such as beta-galactosidase. By the method of pulse induction it appears that distamycin A exterts its inhibiting effect on inducible synthesis at the level of transcription. This effect is probably related to an interference with the positive control of enzyme synthesis performed via the system represented by cyclic AMP and the CRP protein.
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PMID:On the mechanism of inhibition of enzyme induction in Escherichia coli by distamycin A. 17 69

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

Tyramine oxidase in Klebsiella aerogenes is highly specific for tyramine, dopamine, octopamine, and norepinephrine, and its synthesis is induced specifically by these compounds. The enzyme is present in a membrane-bound form. The Km value for tyramine is 9 X 10(-4) M. Tyramine oxidase synthesis was subjected to catabolite repression by glucose in the presence of ammonium salts. Addition of cyclic adenosine 3',5'-monophosphate (cAMP) overcame the catabolite repression. A mutant strain, K711, which can produce a high level of beta-galactosidase in the presence of glucose and ammonium chloride, can also synthesize tyramine oxidase and histidase in the presence of inducer in glucose ammonium medium. Catabolite repression of tyramine oxidase synthesis was relieved when the cells were grown under conditions of nitrogen limitation, whereas beta-galactosidase was strongly repressed under these conditions. A cAMP-requiring mutant, MK54, synthesized tyramine oxidase rapidly when tyramine was used as the sole source of nitrogen in the absence of cAMP. However, a glutamine synthetase-constitutive mutant, MK94, failed to synthesize tyramine oxidase in the presence of glucose and ammonium chloride, although it synthesized histidase rapidly under these conditions. These results suggest that catabolite repression of tyramine oxidase synthesis in K. aerogenes is regulated by the intracellular level of cAMP and an unknown cytoplasmic factor that acts independently of cAMP and is formed under conditions of nitrogen limitation.
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PMID:Regulation of tyramine oxidase synthesis in Klebsiella aerogenes. 17 74

When Bacillus megaterium cells are grown on D-galactose as the sole carbon source, the cells actively synthesize beta-galactosidase (beta-D-galactoside galactohydrolase, EC 3.2.1.23). However, D-galactose, when added to a glucose-grown culture, did not induce beta-galactosidase, apparently because of the glucose inhibition of the transport of galactose. On the other hand, when glucose was added to a galactose-grown culture, the transport of galactose continued at a reduced but significate rate, whereas further synthesis of beta-galactosidase was halted. Adenosine 3',5'-cyclic monophosphate (camp) or guanosine 3',5'-cyclic monophosphate (Cgmp) did not relieve the glucose inhibition of beta-galactosidase synthesis in the preinduced culture. A method which gave a reproducible assay of c[32P]AMP in Escherichia coli did not detect cAMP or cGMP in a B. megaterium culture undergoing beta-galactosidase induction, but revealed the extracellular accumulation of two unknown phosphorylated compounds. Cell-free extracts prepared from galactose-grown cells did not catalyze the degradation of cAMP or cGMP.
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PMID:Evidence against the involvement of adenosine 3',5'-cyclic monophosphate in glucose inhibition of beta-galactosidase induction in Bacillus megaterium. 18 65

1. The dependence of the rate of accumulation of methyl-alpha-D-glucoside on its extracellular concentration was studied in the tgl mutant of Escherichia coli K12, isolated earlier. It has been shown that the kinetics of methyl-alpha-D-glucoside transport differ sharply from those in wild-type bacteria. 2. The beta-galactosidase synthesis in tgl strain is much less sensitive both to permanent and transient glucose catabolite repression. The level of cyclic AMP in mutant cells under the conditions of glucose catabolite repression is several times higher than in the parent strain. 3. The tgl mutation does not affect the manifestation of catabolite inhibition and inducer exclusion with glucose. 4. The data obtained are discussed in the light of a hypothesis concerning the existence of two sites, binding and pecific enzyme II of the phosphoenolpyruvate-dependent phosphotransferase system. The tgl mutation alters the first site, and the second one is damaged by the pgt mutation. 5. It is suggested that the products of the tgl and gpt genes are necessary for the manifestation of the phenomena of glucose permanent and transient repression. The effects of catabolite inhibition and inducer exclusion are realized irrespective of the existence or absence of the tgl product.
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PMID:Glucose effect in tgl mutant of Escherichia col K12 defective in methyl-alpha-D-glucoside transport. 18 55

The uptake of 4-deoxy-4-fluoro-D-glucose (4FG), without subsequent catabolism, by resting cells of Escherichia coli (ATCC 11775) is 0.06 mg/mg dry weight. In frozen-thawed cells of this organism, 4FG is a substrate for the phosphoenolpyruvate phosphotransferase system with a rate of phosphorylation twice that found for the isomeric 3-deoxy-3-fluoro-D-glucose. 4FG is not a carbon source for growth of this organism and it inhibits the extent of growth of cells in the presence of glucose. The inhibition of growth of E. coli K12 on lactose by 4FG is also observed and this is considered to be consistent with the fact that 4FG is an uncompetitive inhibitor of beta-galactosidase (EC 3.2.1.23) activity and that 4FG or 4-deoxy-4-fluoro-D-glucose-6 phosphate repress beta-galactosidase synthesis. These results support the view that catabolite repression may be produced by compounds which are not necessarily metabolised further than hexose-6-phosphates.
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PMID:Some biochemical effects of 4-deoxy-4-fluoro-D-glucose on Escherichia coli. 19 27

A method has been developed for the isolation of Escherichia coli mutants which are resistant to catabolic repression. The method is based on the fact that a mixture of glucose and gluconate inhibits the development of chemotactic motility in the wild type, but not in the mutants. A motile E. coli strain was mutagenized and grown in glucose and gluconate. Mutants which were able to swim into a tube containing a chemotactic attractant (aspartic acid) were isolated. Most of these mutants were able to produce beta-galactosidase in the presence of glucose and gluconate and were normal in their ability to degrade adenosine 3',5-cyclic monophosphate. Some of these mutants were defective in the glucose phosphotransferase system.
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PMID:Isolation and characterization of catabolite repression-resistant mutants of Escherichia coli. 20 Mar 26

The effects of glucose and glucose-6-phosphate in initiating the repression of beta-galactosidase synthesis were studied using a mutant of Escherichia coli K12 which lacks glucose-specific enzyme II of the phosphoenolpyruvate-sugar phosphotransferase system. It was found that glucose-6-phosphate causes transient repression of beta-galactosidase synthesis but glucose does not cause transient repression in this mutant. Evidence was obtained that both the presence of an active transport system for glucose-6-phosphate in the cells and glucose-6-phosphate in the medium are necessary for the initiation of transient repression. No metabolism of glucose-6-phosphate is required. Upon depletion of glucose-6-phosphate in the medium the transient repression was reversed. After the reversal the rate of enzyme synthesis was high in the cells which had been exposed to a high concentration of glucose-6-phosphate. It was concluded that the translocation of glucose-6-phosphate across the membranes is the primary event which affects both the initiation of and the recovery from the transient repression. During the transient repression the cellular content of cyclic adenosine 3',5'-monophosphate decreased significantly.
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PMID:Transient repression of beta-galactosidase synthesis by glucose-6-phosphate in a mutant of Escherichia coli lacking enzyme II specific for glucose in the phosphoenolpyruvate-sugar phosphotransferase system. 20 84

Exogenous addition of guanosine and adenosine 5'-(mono, di and tri) phosphate 3'-diphosphates (pppGpp, ppGpp, pGpp, pppApp, ppApp and pApp) stimulated the synthesis of tryptophanase and beta-galactosidase in permeabilized cells of Escherichia coli. From the results obtained with ppGpp and pppApp, this effect appeared to be at a transcriptional level and depended greatly on the growth condition; the largest effect was observed in cells under shiftdown or grown on poor enrgy source. ppGpp and pppApp, unlike cyclic AMP, did not act to overcome the inhibition of enzyme induction by glucose, but in combination with cyclic AMP caused a synergistic stimulation effect. In the shiftdown cells, ppGpp and pppApp gave 30% or more stimulation effect on tryptophanase induction while cyclic AMP did not stimulate induction. There was therefore a pronounced difference between cyclic AMP and ppGpp or pppApp in stimulatory function.
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PMID:Effect of guanosine 5'-diphosphate 3'-diphosphate and related nucleoside polyphosphates on induction of tryptophanase and beta-galactosidase in permeabilized cells of Escherichia coli. 21 51


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