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)

A cyclic AMP binding protein has been purified over 100-fold from E. coli extracts. Protein purified from wild-type strains binds cyclic AMP with an apparent dissociation constant of 1-2 x 10(-6)M. Two mutant strains that are unresponsive to exogenous cyclic AMP have altered binding activity; the protein purified from one of these mutants has a decreased affinity for cyclic AMP (apparent dissociation constant = 2 x 10(-5)M). Extracts of this mutant are deficient in their ability to support beta-galactosidase synthesis in vitro. The addition of purified, wild-type binding protein to these extracts restores enzyme synthesis toward normal. Because this binding protein appears to be required for cyclic AMP action, we suggest it be called the cyclic AMP receptor protein (CR protein).
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PMID:Cyclic AMP receptor protein of E. coli: its role in the synthesis of inducible enzymes. 431 18

1. Both permanent and transient catabolite repression of beta-galactosidase synthesis in Escherichia coli are abolished by 5mm-3':5'-cyclic-AMP when elicited by glucose, but not when caused by a mixture of glucose, glucose 6-phosphate, gluconate and casein hydrolysate (casamino acids). 2. Glucose uptake is slightly increased by 3':5'-cyclic-AMP. 3. No significant effects of the nucleotide were found on the synthesis of protein and RNA, either in exponential growth on one substrate, or during a growth shift from glycerol to glycerol plus glucose. 4. Marked changes in the soluble-protein profiles of cells growing in glycerol and glucose were caused by the presence of 3':5'-cyclic-AMP. 5. Measurements of (14)CO(2) release from specifically-labelled glucose showed that 3':5'-cyclic-AMP greatly stimulated glycolytic activity while having a minor depressing effect on the metabolic flow through the pentose phosphate cycle. 6. The concentrations of several metabolic intermediates, particularly fructose 1,6-diphosphate, were greatly affected by the presence of 3':5'-cyclic-AMP. 7. Several metabolites partially relieved glucose repression of beta-galactosidase synthesis in EDTA-treated cells; three out of five of these metabolites reversed the effect more effectively than did 3':5'-cyclic-AMP. 8. The evidence for and against a direct role for 3':5'-cyclic-AMP is discussed. It is concluded that the evidence for indirect action is at least as strong as that for direct action.
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PMID:Adenosine 3':5'-cyclic monophosphate and catabolite repression in Escherichia coli. 431 43

1. 5-Phosphorylribose 1-pyrophosphate, in the presence of beta-mercaptoethanol, protected beta-galactosidase from heat inactivation. Many other substances, including 3':5'-cyclic-AMP, were without effect. 2. The efficiency of complementation in vitro of beta-galactosidase segments was decreased by 5-phosphorylribose 1-pyrophosphate but not by 3':5'-cyclic-AMP. Neither substance affected the activity of the complete enzyme. 3. Some indications as to the possible identity of the catabolite repression effector are presented.
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PMID:Interactions between metabolic intermediates and beta-galactosidase from Escherichia coli. 431 44

When an Escherichia coli mutant lacking the enzyme N-acetyl-glucosamine-6-phosphate (AcGN6P) deacetylase is grown in a succinate-mineral salts medium and exposed to an exogenous source of N-acetylglucosamine, approximately 20 to 30 pmoles of AcGN6P per mug of cell dry weight will accumulate in these cells. This accumulation occurs within 2 to 4 min after the addition of N-acetylglucosamine and is coincident with the production of a severe permanent catabolite repression of beta-galactosidase synthesis. This repression does not occur if adenosine 3',5'-cyclic phosphate (cyclic AMP) is added to the cells before AcGN6P accumulates. An immediate derepression occurs when cyclic AMP is added to cells that have already accumulated a large AcGN6P pool. These findings are consistent with the view that low-molecular-weight carbohydrate metabolites and cyclic AMP play key roles in the catabolite repression phenomenon, and that metabolites such as AcGN6P may participate in the represion mechanism by influencing either the formation or degradation of cyclic AMP in E. coli.
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PMID:Cyclic 3',5'-adenosine monophosphate and N-acetylglucosamine-6-phosphate as regulatory signals in catabolite repression of the lac operon in Escherichia coli. 431 36

Catabolite repression is defined as the inhibition of enzyme induction by glucose or related substances. In the bacterium E. coli, the effect of glucose appears to be due to a lowering of the cyclic AMP level. A DNA-directed cell-free system for beta-galactosidase synthesis has served as a model system for studying the mechanism of action of cyclic AMP. Previously, it was reported that in this system cyclic AMP is required for normal initiation of mRNA synthesis. A protein factor which acts in conjunction with the cyclic AMP has been partially purified. This protein factor has a high affinity for cyclic AMP. These and other results presented herein lead us to the conclusion that cyclic AMP and a protein factor called the catabolite gene activator protein are part of a positive control system for activating catabolite-sensitive genes.
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PMID:Mechanism of activation of catabolite-sensitive genes: a positive control system. 432 Apr 61

When Escherichia coli K-12 Hfr.H was induced to synthesize beta-galactosidase in the presence of glucose, an untranslated lactose-specific mRNA (lac-mRNA), protected from decay, was found to accumulate progressively within the cells. The lac-mRNA accumulation was unaffected by the carbon source on which the cells had been grown before the induction. The amount of the lac-mRNA available for translation was affected by catabolite repression and 3':5'-cyclic AMP, but it remained unclear whether this was a direct effect on the formation of the lac-mRNA or a consequence of the effect on its translation.
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PMID:Accumulation of untranslated lactose-specific messenger ribonucleic acid during catabolite repression in Escherichia coli. 433 Jan 49

Recovery from the inhibitory effect of ultraviolet irradiation on the induced synthesis of beta-galactosidase was studied in Escherichia coli B/r. When irradiated cells (520 ergs/mm(2) at 254 nm) were induced and incubated in minimal medium supplemented with Casamino Acids (conditions of catabolite repression), the ability to form enzyme was greatly reduced for about 100 min and then recovery began. The inhibition observed immediately after ultraviolet irradiation was partially reversed by cyclic 3',5'-adenosine monophosphate (cyclic AMP) or by photoreactivation treatment. Inhibition was reduced if the cells were given cold treatment (5 C) before or during irradiation; the kinetics of induced enzyme formation in each case were similar to those of irradiated cells receiving cyclic AMP. These kinetics suggest that the cold treatments, like cyclic AMP, cause the release of the beta-galactosidase-synthesizing system from catabolite repression. When irradiated cells were incubated for various times before cyclic AMP or photoreactivation treatment, some reversal of the inhibition of induced enzyme formation was obtained, but by 100 min the treatments were ineffective. Because 100 min was also the time at which dark recovery of enzyme formation began, the recovery process was interpreted to be the result of completion of DNA repair, which, in turn, released the beta-galactosidase-synthesizing system from catabolite repression.
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PMID:Release of the -galactosidase-synthesizing system from ultraviolet catabolite repression by cyclic 3',5'-adenosine monophosphate, dark repair, photoreactivation, and cold treatment. 433 80

Caulobacter crescentus goes through a series of morphological changes during its life cycle, including the coincident expression of synthesis of flagella, pili, and receptor sites for DNA bacteriophage. Upon transfer of a mixed population of cells to medium containing lactose as the sole carbon source, these changes were blocked for about 20 hr until beta-galactosidase activity became apparent. The addition of dibutyryl cyclic AMP to the blocked cultures brought about the resumption of cell differentiation, growth, and the appearance of beta-galactosidase activity within 1 hr. Unlike Escherichia coli, the intracellular and extracellular concentrations of cyclic AMP in C. crescentus did not vary under several growth conditions, including catabolite repression. It would appear, therefore, that although there is an effect of cyclic AMP on the induction of beta-galactosidase and differentiation in C. crescentus, regulation of these processes occurs without consistent changes in the cellular level of this nucleotide.
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PMID:Effect of dibutyryladenosine 3':5'-cyclic monophosphate on growth and differentiation in Caulobacter crescentus. 433 85

In a temperature-sensitive mutant of Escherichia coli, beta-galactosidase cannot be induced at the nonpermissive temperature (43 degrees C) without the addition of exogenous 3', 5'-cyclic AMP (cAMP), although the intracellular concentration of this nucleotide is normal. This specific effect of cAMP is probably general in this strain for those operons which are controlled by the cAMP receptor protein and cAMP, but not for other parts of the chromosome. The lac mRNA produced at 43 degrees C in absence of cAMP is transcribed from the correct DNA strand and it directs the synthesis of enzymatically inactive material cross-reacting with beta-galactosidase. Experiments separating transcription from translation by using rifampicin, suggest that cAMP exerts its effect during initiation of transcription or translation of lac mRNA, but does not affect the propagation of either the messenger or of the beta-galactosidase polypeptide chain.
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PMID:A messenger RNA from the lactose operon of Escherichia coli that can not direct the production of functional -galactosidase in absence of exogenous adenosine 3',5-cyclic monophosphate. 433 29

The concentration of cyclic adenosine 3',5'-monophosphate (c-AMP) in Escherichia coli growing on different sources of carbon was studied. Cultures utilizing a source of carbon that supported growth relatively poorly had consistently higher concentrations of c-AMP than did cultures utilizing sugars that supported rapid growth. This relationship was also observed in strains defective in c-AMP phosphodiesterase and simultaneously resistant to catabolite repression; in such strains the c-AMP concentration was slightly higher for several sources of carbon tested. Cultures continued to synthesize c-AMP and secreted it into the medium, under conditions that brought about an inhibition of the intracellular accumulation of the cyclic nucleotide. Transient repression of the synthesis of beta-galactosidase was not associated with an abrupt decrease in the cellular concentration of c-AMP.
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PMID:Cyclic adenosine 3',5'-monophosphate in Escherichia coli. 435 86


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