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PubMed1975

Catabolite repression in Escherichia coli K12 mutants defective in glucose transport.

The phenomenon of glucose catabolite repression was studied in Escherichia coli mutants unable to transport this carbohydrate. The pts I,H mutant P34 was much less sensitive to permanent and transient repressive effect of glucose on beta-galactosidase synthesis than parental type. The 1103 mutant with lack of enzyme 1 of the phosphoenolpyruvate-dependent phosphotransferase system (ptsI) behaves as well as P34 mutant after addition of glucose to casamino acids mineral medium. But in minimal medium with succinate as the sole source of carbon cells of the 1103 mutant (in accordance with the data of Perlman and Pastan, 1969) show hightened sensibility to transient glucose repression. The effect of hypersensibility disappears when the lacI mutation rendering the beta-galactosidase synthesis to costitutivity is introduced in 1103 mutant. It is shown that the hightened sensibility of beta-galactosidase synthesis to glucose transient repression in 1103 mutant is not an effect of the pts mutation and most probably is due to "inducer exclusion" of the lac operon. It is also shown that if one introduces the P34 mutation in strain devoided of one of the enzymes II for glucose (gptA) (and due to this resistant to glucose catabolite repression) then the level of resistance in double mutant does not increase in spite of considerable supression of 14C glucose accumulation. It is discussed the role of separate components of Escherichia coli K12 glucose transport system in realization of the phenomenon of catabolite repression.

Biological Transport↗
PubMed1999

Catabolite repression of the xylanase gene (xynA) expression in Bacillus stearothermophilus no. 236 and B. subtilis.

Catabolite repression of the Bacillus stearothermophilus No. 236 xynA gene, encoding an extracellular xylanase, was investigated in this work. Expression of the xynA gene in the B. stearothermophilus strain was found to be subject to glucose catabolite repression, and the level of repression was about 50-fold when the relative amounts of xynA transcript synthesized on different carbon sources were analyzed. The experiments with the B. subtilis MW15 strains carrying plasmids containing the xynA::aprA fusion gene showed that the cloned xynA gene did not require any specific carbon source for its induction. Nevertheless, the expression of the cloned gene was repressed by the presence of glucose. From the nucleotide sequence of the cloned xynA gene, we found two potential catabolite responsive elements (cre) within its reading frame region (cre-1: nucleotides +160 to +173 and cre-2: +173 to +186). Furthermore, by using various deletion derivatives of the xynA::aprA fusion plasmid (pMGW23), we suggested that only the cre-2 element might play a role in the glucose catabolite repression. Repression level of the xynA gene expression in the recombinant B. subtilis strain was estimated to be about 3-fold by analysis of the amounts of xynA transcript.

Bacillus subtilis↗
PubMed1985

Barotolerant variant of Streptococcus faecalis with reduced sensitivity to glucose catabolite repression.

Physiological characterization of the APR-11 variant of Streptococcus faecalis ATCC 9790 revealed that the variant has reduced sensitivity to glucose catabolite repression. This reduced sensitivity was indicated by the synthesis of enzymes for catabolism of lactose or arginine in cultures growing at 0.1, 40, or 70 MPa in media with levels of glucose highly repressive for the parent strain. Reduced catabolite repression appeared to be due to reduced activity of the glucose-specific, phosphotransferase system in APR-11 cells. Conversion of pyruvate to lactate or to acetate and ethanol did not appear to be altered in the variant. The APR-11 variant produced a greater final yield of biomass than the parent at all pressures tested, and its barotolerance was especially marked in media with low levels of glucose and high levels of lactose in which derepression of the lactose catabolic system was necessary for full growth. Overall, the greater barotolerance of the APR-11 strain appeared to be due to its enhanced capacity for catabolism related to its reduced sensitivity to catabolite repression by glucose.

Acetates↗
PubMed1999

The PalkBFGHJKL promoter is under carbon catabolite repression control in Pseudomonas oleovorans but not in Escherichia coli alk+ recombinants.

The alk genes are located on the OCT plasmid of Pseudomonas oleovorans and encode an inducible pathway for the utilization of n-alkanes as carbon and energy sources. We have investigated the influence of alternative carbon sources on the induction of this pathway in P. oleovorans and Escherichia coli alk+ recombinants. In doing so, we confirmed earlier reports that induction of alkane hydroxylase activity in pseudomonads is subject to carbon catabolite repression. Specifically, synthesis of the monooxygenase component AlkB is repressed at the transcriptional level. The alk genes have been cloned into plasmid pGEc47, which has a copy number of about 5 to 10 per cell in both E. coli and pseudomonads. Pseudomonas putida GPo12 is a P. oleovorans derivative cured of the OCT plasmid. Upon introduction of pGEc47 in this strain, carbon catabolite repression of alkane hydroxylase activity was reduced significantly. In cultures of recombinant E. coli HB101 and W3110 carrying pGEc47, induction of AlkB and transcription of the alkB gene were no longer subject to carbon catabolite repression. This suggests that carbon catabolite repression of alkane degradation is regulated differently in Pseudomonas and in E. coli strains. These results also indicate that PalkBFGHJKL, the Palk promoter, might be useful in attaining high expression levels of heterologous genes in E. coli grown on inexpensive carbon sources which normally trigger carbon catabolite repression of native expression systems in this host.

Alkanes↗
PubMed1991

A yeast protein with homology to the beta-subunit of G proteins is involved in control of heme-regulated and catabolite-repressed genes.

The product of the Saccharomyces cerevisiae AER2 gene is responsible for maintaining repression of at least two distinct regulatory pathways: heme activation/repression and catabolite repression. Mutations in the gene caused an eightfold increase in the expression of the heme-activated CYC1 gene in the absence of heme, a substantial increase in the expression of the heme-repressed ANB1 gene in the presence of heme, and a 13-fold increase in the expression of the catabolite-repressed GAL1 gene in the presence of glucose. Lesser or no increases in the expression of these genes were observed under derepressed or activation conditions. The aer2 mutations also caused a large increase in CYC7 gene expression under all conditions; this gene is subject to heme activation/repression, as well as catabolite repression. The AER2 gene was cloned and the sequence determined. The large open reading frame contiguous with the transcript from the complementing region encoded a 713-amino acid polypeptide chain with extensive homology to the beta-subunit of G proteins. The sequence revealed that AER2 is the TUP1 gene. A deletion mutation was constructed and the null phenotype was the same as the original mutants. The aer2 null mutant was shown to have increased aerobic and anaerobic levels of RNA encoding the ROX1 repressor, normally expressed only aerobically and responsible for the aerobic repression of ANB1 expression. The increase in both ROX1 and ANB1 RNAs aerobically in this mutant suggests that the repressor is nonfunctional in the mutant.

Amino Acid Sequence↗
PubMed1969

Relaxation of catabolite repression in streptomycin-dependent Escherichia coli.

Acetohydroxy acid synthetase, which is sensitive to catabolite repression in wild-type Escherichia coli B, was relatively resistant to this control in a streptomycin-dependent mutant. The streptomycin-dependent mutant was found to be inducible for beta-galactosidase in the presence of glucose, although repression of beta-galactosidase by glucose occurred under experimental conditions where growth of the streptomycin-dependent mutant was limited. Additional glucose-sensitive enzymes of wild-type E. coli B (citrate synthase, fumarase, aconitase and isocitrate dehydrogenase) were found to be insensitive to the carbon source in streptomycin-dependent mutants: these enzymes were formed by streptomycin-dependent E. coli B in equivalent quantities when either glucose or glycerol was the carbon source. Two enzymes, glucokinase and glucose 6-phosphate dehydrogenase, that are glucose-insensitive in wild-type E. coli B were formed in equivalent quantity on glucose or glycerol in both streptomycin-sensitive and streptomycin-dependent E. coli B. The results indicate a general decrease or relaxation of catabolite repression in the streptomycin-dependent mutant. The yield of streptomycin-dependent cells from glucose was one-third less than that of the streptomycin-sensitive strain. We conclude that the decreased efficiency of glucose utilization in streptomycin-dependent E. coli B is responsible for the relaxation of catabolite repression in this mutant.

Carbonic Anhydrases↗
PubMed1989

Bacillus licheniformis alpha-amylase gene, amyL, is subject to promoter-independent catabolite repression in Bacillus subtilis.

Expression of the Bacillus licheniformis alpha-amylase gene, amyL, was temporally activated and subject to catabolite repression both in its natural host and when cloned on a 3.55-kilobase fragment in Bacillus subtilis. A subclone from which the promoter region of amyL and sequences upstream from the promoter were deleted had a low level of amylase activity. Expression of the promoterless gene was still subject to repression by glucose when the gene was present either on a multicopy plasmid or integrated into the B. subtilis chromosome. Catabolite repression occurred independently of the amylase promoter and irrespective of the distance of the promoterless amyL gene from the promoter which transcribed it. The transcriptional start sites of amyL activated by its own promoter and by a vector sequence promoter were determined by S1 mapping. alpha-Amylase-specific mRNA levels were measured in repressing and nonrepressing media, and catabolite repression was found to act at the level of transcription.

Bacillus↗
PubMed1999

Structure-function analysis of yeast hexokinase: structural requirements for triggering cAMP signalling and catabolite repression.

In baker's yeast (Saccharomyces cerevisiae) the hexokinases PI (Hxk1) and PII (Hxk2) are required for triggering of the activation of the Ras-cAMP pathway and catabolite repression. Specifically, Hxk2 is essential for the establishment of glucose repression, whereas either Hxk1 or Hxk2 can sustain fructose repression. Previous studies have suggested that the extent of glucose repression is inversely correlated with hexokinase catalytic activity and hence with an adequate elevation of intracellular sugar phosphate levels. However, several lines of evidence indicate that glucose 6-phosphate is not the trigger of catabolite repression in yeast. In the present study we employed site-directed mutagenesis of amino acids important for the binding of sugar and ATP, for efficient phosphoryl transfer and for the closure of the substrate-binding cleft, to obtain an insight into the structural requirements of Hxk2 for sugar-induced signalling. We show that the ATP-binding Lys-111 is not essential for catalysis in vivo or for signal triggering. Substitution of the catalytic-centre Asp-211 caused loss of catalytic activity, but high-affinity sugar binding was retained. However, this was not sufficient to cause cAMP activation nor catabolite repression. Mutation of Ser-158 abrogated glucose-induced, but not fructose-induced, repression. Moreover, 2-deoxyglucose sustained repression despite an extremely low catalytic activity. We conclude that the establishment of catabolite repression is dependent on the onset of the phosphoryl transfer reaction on hexokinase and is probably related to the stable formation of a transition intermediate and concomitant conformational changes within the enzyme. In contrast, the role of Hxk2 in Ras-cAMP activation seems to be directly connected to its catalytic function. The implications of this model are discussed.

Amino Acid Sequence↗
PubMed1968

Effect of amino sugars on catabolite repression in Escherichia coli.

N-acetylglucosamine was found to be a good repressor source for catabolite repression of the beta-galactosidase system in Escherichia coli. It was found capable of increasing the severity of repression by glucose or gluconate when included in the medium with either of these substrates. N-acetylglucosamine was shown to be assimilated under these conditions, but had no effect on culture growth rates. Its influence on catabolite repression was not altered by growth in the presence of inhibiting levels of penicillin. These findings indicated that catabolite repression may be associated with certain reactions of amino sugar metabolism. A working model has been formulated along these lines and will be used to explore this possible relationship further.

Carbon Isotopes↗
PubMed1992

Catabolite repression of the xyl operon in Bacillus megaterium.

We characterized catabolite repression of the genes encoding xylose utilization in Bacillus megaterium. A transcriptional fusion of xylA encoding xylose isomerase to the spoVG-lacZ indicator gene on a plasmid with a temperature-sensitive origin of replication was constructed and efficiently used for single-copy replacement cloning in the B. megaterium chromosome starting from a single transformant. In the resulting strain, beta-galactosidase expression is 150-fold inducible by xylose and 14-fold repressed by glucose, showing that both regulatory effects occur at the level of transcription. Insertion of a kanamycin resistance gene into xylR encoding the xylose-dependent repressor leads to the loss of xylose-dependent regulation and to a small drop in the efficiency of glucose repression to eightfold. Deletion of 184 bp from the 5' part of the xylA reading frame reduces glucose repression to only twofold. A potential glucose-responsive element in this region is discussed on the basis of sequence similarities to other glucose-repressed genes in Bacillus subtilis. The sequence including the glucose-responsive element is also necessary for repression exerted by the carbon sources fructose and mannitol. Their efficiencies of repression correlate to the growth rate of B. megaterium, as is typical for catabolite repression. Glycerol, ribose, and arabinose exert only a basal twofold repression of the xyl operon, which is independent of the presence of the cis-active glucose-responsive element within the xylA reading frame.

Aldose-Ketose Isomerases↗
PubMed2002

Carbon catabolite repression in bacteria: choice of the carbon source and autoregulatory limitation of sugar utilization.

Carbon catabolite repression (CCR) in bacteria is generally regarded as a regulatory mechanism to ensure sequential utilization of carbohydrates. Selection of the carbon sources is mainly made at the level of carbohydrate-specific induction. Since virtually all carbohydrate catabolic genes or operons are regulated by specific control proteins and require inducers for high level expression, direct control of the activity of regulators or control of inducer formation is an efficient measure to keep them silent. By these mechanisms, bacteria are able to establish a hierarchy of sugar utilization. In addition to the control of induction processes by CCR, bacteria have developed global transcriptional regulation circuits, in which pleiotropic regulators are activated. These global control proteins, the catabolite gene activator protein (CAP), also known as cAMP receptor protein, in Escherichia coli or the catabolite control protein (CcpA) in Gram-positive bacteria with low GC content, act upon a large number of catabolic genes/operons. Since practically any carbon source is able to trigger global transcriptional control, expression of sugar utilization genes is restricted even in the sole presence of their cognate substrates. Consequently, CAP- or CcpA-dependent catabolite repression serves as an autoregulatory device to keep sugar utilization at a certain level rather than to establish preferential utilization of certain carbon sources. Together with other autoregulatory mechanisms that are not acting at the gene expression level, CCR helps bacteria to adjust sugar utilization to their metabolic capacities. Therefore, catabolic/metabolic balance would perhaps better describe the physiological role of this regulatory network than the term catabolite repression.

Bacteria↗
PubMed1982

Genetic evidence for a role of hexokinase isozyme PII in carbon catabolite repression in Saccharomyces cerevisiae.

A mutant of Saccharomyces cerevisiae that was selected for resistance to carbon catabolite repression also had reduced hexokinase activity. Hexokinase isoenzymes were purified from mutant and wild type cells. The specific glucokinase and hexokinase isozyme PI were present at normal levels in mutant and wild type, but no hexokinase isozyme PII activity was detected in the mutant. Staining for enzyme activity after electrophoresis of crude extracts also indicated that hexokinase PII was absent in the mutant. Mutant and wild type segregants gained by tetrad analysis were investigated electrophoretically. Staining for enzyme activity confirmed that catalytically inactive hexokinase PII and the defect in carbon catabolite repression always co-segregated. The results support the hypothesis that hexokinase PII might mediate carbon catabolite repression.

Enzyme Repression↗
PubMed1968

N-acetylglucosamine assimilation in Escherichia coli and its relation to catabolite repression.

The ability of N-acetylglucosamine to enhance catabolite repression by glucose was studied by using cultures grown on a combination of these substrates. Under these conditions, it was shown that two-thirds of the N-acetylglucosamine utilized was routed into dissimilatory pathways, whereas the remaining one-third was channeled into biosynthesis. It was established that over 50% of the N-acetylglucosamine assimilated was incorporated directly into amino sugar polymers. It was also shown that this exogenous supply of N-acetylglucosamine was in fact used preferentially over glucose as the precursor for amino sugar polymer biosynthesis. These findings provided support for the prediction that catabolite repression in Escherichia coli may be interrelated with certain reactions involved in amino sugar biosynthesis.

Carbon Dioxide↗
PubMed1971

Induction specificity and catabolite repression of the early enzymes in camphor degradation by Pseudomonas putida.

The ability of bornane and substituted bornanes to induce the early enzymes for d(+)-camphor degradation and control of these enzymes by catabolite repression were studied in a strain of a Pseudomonas putida. Bornane and 20 substituted bornane compounds showed induction. Of these 21 compounds, bornane and 8 of the substituted bornanes provided induction without supporting growth. Oxygen, but not nitrogen, enhanced the inductive potency of the unsubstituted bornane ring. All bornanedione isomers caused induction, and those with substituents on each of the three consecutive carbon atoms, including the methyl group at the bridgehead carbon, showed induction without supporting growth. Although it was not possible to obtain experimental data for a case of absolute gratuitous induction by compounds not supporting growth, indirect evidence in support of gratuitous induction is presented. It is proposed that the ability of P. putida to tolerate the unusually high degree of possible gratuitous induction observed for camphor catabolism may be related to the infrequent occurrence of bicyclic ring structures in nature. Survival of an organism with a broad specificity for gratuitous induction is discussed. Glucose and succinate, but not glutamate, produced catabolite repression of the early camphor-degrading enzymes. Pathway enzymes differ in their degree of sensitivity to succinate-provoked catabolite repression. The ability of a compound to produce catabolite repression is not, however, directly related to the duration of the lag period (diauxic lag) between growth on camphor and growth on the repressing compound.

Alcohol Oxidoreductases↗
PubMed1983

Effect of growth conditions on catabolite repression and cyclic AMP synthesis in Escherichia coli 3000A1.

Catabolite repression of beta-galactosidase synthesis in E. coli 3000A1 (adenine-) was studied under a variety of growth conditions. The differential rate of induced beta-galactosidase synthesis was maximal at the growth rate of 0.75 division per h, irrespective of whether growth conditions were aerobic or anaerobic. The addition of cyclic AMP (cAMP) to the medium partly restored the repressed synthesis of beta-galactosidase under some growth conditions, but showed little or no effect on the enzyme synthesis under other conditions. Although growth rate and profile of beta-galactosidase synthesis in glucose-grown cells were similar to those in arabinose-grown cells, the acceleration of beta-galactosidase synthesis upon the addition of cAMP was found only in glucose-grown cells. The cells aerobically grown in the presence of glycerol, xylose, or arabinose showed a high synthetic rate of cAMP and were insensitive to exogenously supplied cAMP as regards beta-galactosidase synthesis. Although the cells grown with glucose showed similar rates of cAMP synthesis under aerobic and anaerobic conditions, the differential rate of beta-galactosidase synthesis was much higher in the anaerobic state than in the aerobic state. These findings support the idea that catabolite repression found in the strain is caused through two mechanisms, i.e., cAMP-mediated and cAMP-independent ones.

Bacterial Proteins↗
PubMed1975

Penicillinamidohydrolase in Escherichia coli. III. Catabolite repression, diauxie, effect of cAMP and nature of the enzyme induction.

Synthesis of penicillinamidohydrolase (penicillin acylase, EC 3.5.1.11) in Escherichia coli is subjected to the absolute catabolite repression by glucose and partial repression by acetate. Both types of catabolite repression of synthesis of the enzyme in Escherichia coli are substantially influenced by cyclic 3',5'-adenosinemonophosphate (cAMP). Growth diauxie in a mixed medium containing glucose and phenylacetic acid serving as carbon and energy sources is overcome by cAMP. cAMP does not influence the basal rate of the enzyme synthesis (without the inducer). Derepression of synthesis of penicillinamidohydrolase by cAMP in a medium with glucose and inducer (phenylacetic acid) is associated with utilization of the inducer, due probably to derepression of other enzymes responsible for degradation of phenylacetic acid. Lactate can serve as a "catabolically neutral" source of carbon suitable for the maximum production of penicillinamidohydrolase. The gratuitous induction of the enzyme synthesis in a medium with lactate as the carbon and energy source and with phenylacetic acid is not influenced by cAMP; however, cAMP overcomes completely the absolute catabolite repression of the enzyme synthesis by glucose.

Acetates↗
PubMed1994

Glucose kinase has a regulatory role in carbon catabolite repression in Streptomyces coelicolor.

A glucose kinase (glkA) mutant of Streptomyces coelicolor A3(2) M145 was selected by the ability to grow in the presence of the nonmetabolizable glucose analog 2-deoxyglucose. In this glkA mutant, carbon catabolite repression of glycerol kinase and agarase was relieved on several carbon sources tested, even though most of these carbon sources are not metabolized via glucose kinase. This suggests that catabolite repression is not regulated by the flux through glucose kinase and that the protein itself has a regulatory role in carbon catabolite repression. A 10-fold overproduction of glucose kinase also results in relief of catabolite repression, suggesting that excess glucose kinase can titrate the repressing signal away. This could be achieved directly by competition of excess glucose kinase with its repressing form for binding sites on DNA promoter regions or indirectly by competition for binding of another regulatory protein.

Base Sequence↗