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)

1. Acute transient catabolite repression of beta-galactosidase synthesis, observed when glucose is added to glycerol-grown cells of Escherichia coli (Moses & Prevost, 1966), requires the presence of a functional operator gene (o) in the lactose operon. Total deletion of the operator gene abolished acute transient repression, even in the presence of a functional regulator gene (i). 2. Regulator constitutives (i(-)) also show transient repression provided that the operator gene is functional. Regulator deletion mutants (i(del)), with which to test specifically the role of the i gene, have not so far been available. 3. The above mutants, showing various changes in the lactose operon, show no alteration in the effect of glucose on induced tryptophanase synthesis. Glucose metabolism, as measured in terms of the release of (14)CO(2) from [1-(14)C]glucose and [6-(14)C]glucose, also showed no differences between strains exhibiting or not exhibiting transient repression. This suggests no change in the operation of the pentose phosphate cycle, a metabolic activity known to be of paramount importance for glucose repression of beta-galactosidase synthesis (Prevost & Moses, 1967). 4. Chronic permanent repression by glucose of beta-galactosidase synthesis (less severe in degree than acute transient repression) persists in strains in which transient repression has been genetically abolished. Constitutive alkaline-phosphatase synthesis, which shows no transient repression, also demonstrates chronic permanent repression by glucose. 5. Chloramphenicol repression also persists in mutants with no transient repression, and also affects alkaline phosphatase. It is suggested that chronic permanent repression and chloramphenicol repression are non-specific, and that they do not influence beta-galactosidase synthesis via the regulatory system of the lactose operon.
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PMID:Involvement of the lac regulatory genes in catabolite repression in Escherichia coli. 534 Mar 65

Tryptophan oxygenase (tryptophan 2,3-dioxygenase) activity increases immediately before the initiation of actinomycin D production by Streptomyces parvullus. We have attempted to discern whether this increase is due to a release from catabolite repression or to the synthesis of an inducer substance. The standard culture medium (glutamic acid-histidine-fructose medium) used in antibiotic production studies with S. parvullus contains l-glutamate as a major constituent. l-Glutamate is almost totally consumed before the onset of actinomycin D synthesis. The addition of 10 mM l-glutamate at this stage completely abolished actinomycin D production as well as tryptophan oxygenase synthesis. Fourteen amino acids were tested for a similar effect. Of these, l-glutamate and l-aspartate had the most dramatic effect on tryptophan oxygenase and beta-galactosidase (beta-d-galactosidase), another inducible enzyme. Standard glutamic acid-histidine-fructose medium, preincubated for 23 h to remove l-glutamate, allowed the synthesis of actinomycin D and tryptophan oxygenase by cells at a stage of growth normally considered too early for antibiotic production. A chemically defined medium lacking l-glutamate and adjusted to pH 8.0 was designed to simulate the preincubation medium. The transfer of cells to this artificial preincubation medium resulted in the appearance of tryptophan oxygenase as early as 19 h before normal synthesis occurred, eliminating the possibility that an inducer molecule is synthesized and excreted during the preincubation period. The results of these studies suggest that the increase in tryptophan oxygenase activity before the onset of actinomycin D synthesis, as well as the synthesis of actinomycin D itself, is due to a release from l-glutamate catabolite repression.
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PMID:Control of actinomycin D biosynthesis in Streptomyces parvullus: regulation of tryptophan oxygenase activity. 611 49

When inducing simultaneously beta-galactosidase and tryptophanase in a batch culture either the synthesis of tryptophanase or of both enzymes is decreased due to an insufficient cAMP concentration. The addition of this nucleotide can overcome this decrease. In a continuous culture both enzymes are synthesized at the maximum rate, as the amount of cAMP produced during carbon limitation of growth is probably sufficient for the simultaneous synthesis of both enzymes. In the beta-galactosidase hyperproduction mutant cultivated continuously the level of beta-galactosidase markedly decreases when tryptophanase is simultaneously induced. Also this decrease is caused by cAMP insufficiency and can be overcome by increasing its concentration. cAMP is thus an important regulatory factor of both enzymes and becomes a limiting factor in their simultaneous synthesis; a competition for this regulatory compound apparently occurs and probably also a different mutual affinity of the regulatory complex with the promoter site of the enzyme operons is involved.
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PMID:Effect of cyclic adenosine-3',5'-monophosphate on the simultaneous synthesis of beta-galactosidase and tryptophanase in Escherichia coli. 624 99

During a simultaneous induction of three enzymes which are subject to catabolite repression (beta-galactosidase, tryptophanase and amylomaltase, or beta-galactosidase, tryptophanase and D-serine deaminase) in a batch culture, the rates of synthesis of beta-galactosidase and tryptophanase decreases, while the rates of synthesis of amylomaltase and D-serine deaminase remain unaffected. The addition of cAMP brings about a considerable increase of the rate of synthesis of D-serine deaminase and a partial synthesis rate increase of beta-galactosidase whihle the synthesis rate of tryptophanase remains lowered and the synthesis rate of amylomaltase remains unaffected. In a continuous culture beta-galactosidase, tryptophanase and D-serine deaminase are synthesized simultaneously at a maximum rate without mutual influence. The addition of cAMP increases the rate of synthesis of all three enzymes.
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PMID:Simultaneous induction of three catabolic enzymes in Escherichia coli. 624 3

Strain MM6-13 (ptsI suc lacI sup) of Escherichia coli contains a suppressor of the succinate-negative phenotype. In MM6-13, sup caused enhanced growth in glycerol, maltose, melibiose, and succinate media and increased activity of beta-galactosidase and tryptophanase relative to an isogenic strain without sup. In strain A61 (cya sup), sup partially suppressed cya. Cyclic guanosine monophosphate increased beta-galactosidase activity sevenfold in A61 and enabled this strain to grow on maltose, galactose, succinate, and arabinose. Strain A61 responded to much lower concentrations of cyclic adenosine monophosphate than cyclic guanosine monophosphate. It appears that sup is located in the crp locus. These results suggest that sup mutants have an altered cyclic adenosine monophosphate receptor protein which is activated by cyclic guanosine monophosphate and has an increased affinity for cyclic adenosine monophosphate.
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PMID:Suppression of defects in cyclic adenosine 3',5'-monophosphate metabolism in Escherichia coli. 625 91

Pleiotropic carbohydrate-positive pseudorevertants have been isolated from a specific class of rho-crp double mutants of Escherichia coli carrying both defective transcription termination protein, rho, and cyclic AMP receptor protein. The modulation of catabolite repression of beta-galactosidase, amylomaltase, and tryptophanase has been studied in the pseudorevertants. It has been found that these mutants exhibit catabolite repression. Because catabolite-sensitive operons can be expressed in the absence of functional cyclic AMP receptor protein, this would suggest on the one hand that the cyclic AMP-receptor protein complex is not the exclusive mediator of catabolite repression and on the other hand that rho might be involved in the regulation of catabolite-sensitive operons.
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PMID:Catabolite repression in Escherichia coli mutants lacking cyclic AMP receptor protein. 625 66

Intracellular concentration of cAMP regulates the synthesis of enzymes sensitive to catabolite repression. The relationship between the single and multiple induction of beta-galactosidase (EC 3.2.1.23), L-tryptophanase (EC 4.1.99.1), D-serine deaminase (EC 4.2.1.14), L-asparaginase (EC 3.5.1.1) and L-malate dehydrogenase (EC 1.1.1.37) was studied and the effect of cAMP level on the induction in Escherichia coli Crookes (ATCC 8739) was investigated. A varying degree of catabolite repression was observed during induction of individual enzymes induced separately on different energy sources. The synthesis of l-tryptophanase was most sensitive, whereas l-asparaginase was not influenced at all. Exogenous cAMP was found to overcome partially the catabolite repression of beta-galactosidase and D-serine deaminase, both during single induction. The synthesis of l-malate dehydrogenase was negatively influenced by the multiple induction even in the presence of cAMP; on the other hand, the synthesis of l-tryptophanase was stimulated, independently of the level of the exogenous cAMP. Similarly, the activity of L-asparaginase slightly but significantly increased during the multiple induction of all five enzymes; here too the activity increase did not depend on exogenous cAMP.
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PMID:Catabolite repression during single and multiple induction in Escherichia coli. 625 31

Mutations in top, the structural gene for Escherichia coli DNA topoisomerase I, have been identified and mapped at 28 min on the chromosome, near cysB. Strains carrying deletions of the top gene are viable. The top mutations, however, do exert pleiotropic effects on transcription and transposition. Mutants lacking DNA topoisomerase I have a more rapid rate of induction and a higher level of catabolite-sensitive enzymes including tryptophanase and beta-galactosidase. This general activation of transcription by top mutations can be attributed to an increase in the negative superhelicity of the DNA in vivo when the topoisomerase activity is abolished. The frequency of transposition of Tn5, a transposon carrying kanamycin resistance, is decreased by a factor of 40 or more in top mutants. A direct or indirect role of the topoisomerase in transposition is discussed. The transposition frequency of Tn3, however, is not dependent on top. Based on the studies of the E. coli top mutants, it appears that the supX gene, which was originally studied in Salmonella typhimurium [Dubnau, E. & Margolin, P. (1972) Mol. Gen. Genet. 117, 91-112] is likely to be the structural gene for DNA topoisomerase I.
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PMID:Mutations in the gene coding for Escherichia coli DNA topoisomerase I affect transcription and transposition. 626 7

When a wild-type strain of Escherichia coli B was cultured on a medium containing L-aspartic acid as the sole carbon source (Asp-C medium), aspartase formation was higher than that observed in minimal medium. Addition of glucose to Asp-C medium decreased aspartase formation. When also cultured in a medium containing L-aspartic acid as the sole nitrogen source (Asp-N medium), E. coli B showed a low level of aspartase formation and an elongated doubling time. To obtain aspartase-hyperproducing strains, we enriched cells growing faster than cells of the wild-type strain in Asp-N medium by continuous cultivation of mutagenized cells. After plate selection, the doubling times of these mutants were measured. Thereafter, fast-growing mutants were tested for aspartase formation. One of these mutants, strain EAPc7, had a higher level of aspartase formation than did the wild-type strain in medium containing L-aspartic acid as the carbon source, however; addition of glucose to this medium decreased aspartase formation. The other mutant, strain EAPc244, had a higher level of aspartase activity than did the wild-type strain in both media. Therefore, aspartase formation in mutant EAPc244 was released from catabolite repression. In strain EAPc244 the other catabolite-repressible enzymes, beta-galactosidase, tryptophanase, and the three tricarboxylic acid cycle enzymes, were also released from catabolite repression. Both mutants had sevenfold the aspartase formation of the wild-type strain in a medium which contained fumaric acid as the main carbon source and which has been used for industrial production of E. coli B aspartase. However, strain EAPc244 had 2.5-fold the fumarase activity of strain EAPc7.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Aspartase-hyperproducing mutants of Escherichia coli B. 639 73

Low concentrations of urea specifically inhibit the expression of catabolite sensitive genes (the lactose, galactose and maltose operons and the tryptophanase gene). This inhibition depends upon growth conditions, i.e. carbon source and temperature. The main effect of urea is exerted at the level of transcription initiation. However an additional inhibitory effect is observed on the decay and expression of the beta-galactosidase messenger. In a strain harboring the UV5 mutation in the lactose promoter, the effect at the level of transcription is relieved while the effect on the decay and the expression of the beta-galactosidase messenger remains the same. Just like the extreme physiological catabolite repression, the urea effect occurs even in a cya delta strain and is not antagonized by addition of adenosine 3'-5' cyclic monophosphate.
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PMID:The effect of urea on catabolite sensitive operons in Escherichia coli K 12. 699 57


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