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PubMed2005

A quantitative approach to catabolite repression in Escherichia coli.

A dynamic mathematical model was developed to describe the uptake of various carbohydrates (glucose, lactose, glycerol, sucrose, and galactose) in Escherichia coli. For validation a number of isogenic strains with defined mutations were used. By considering metabolic reactions as well as signal transduction processes influencing the relevant pathways, we were able to describe quantitatively the phenomenon of catabolite repression in E. coli. We verified model predictions by measuring time courses of several extra- and intracellular components such as glycolytic intermediates, EII-ACrr phosphorylation level, both LacZ and PtsG concentrations, and total cAMP concentrations under various growth conditions. The entire data base consists of 18 experiments performed with nine different strains. The model describes the expression of 17 key enzymes, 38 enzymatic reactions, and the dynamic behavior of more than 50 metabolites. The different phenomena affecting the phosphorylation level of EIIACrr, the key regulation molecule for inducer exclusion and catabolite repression in enteric bacteria, can now be explained quantitatively.

Carbohydrate Metabolism↗
PubMed1974

Catabolite repression and derepression of arylsulfatase synthesis in Klebsiella aerogenes.

When a mutant (Mao(-)) of Klebsiella aerogenes lacking an enzyme for tyramine degradation (monoamine oxidase) was grown with d-xylose as a carbon source, arylsulfatase was repressed by inorganic sulfate and repression was relieved by tyramine. When the cells were grown on glucose, tyramine failed to derepress the arylsulfatase synthesis. When grown with methionine as the sole sulfur source, the enzyme was synthesized irrespective of the carbon source used. Addition of cyclic adenosine monophosphate overcame the catabolite repression of synthesis of the derepressed enzyme caused by tyramine. Uptake of tyramine was not affected by the carbon source. We isolated a mutant strain in which derepression of arylsulfatase synthesis by tyramine occurred even in the presence of glucose and inorganic sulfate. This strain also produced beta-galactosidase in the presence of an inducer and glucose. These results, and those on other mutant strains in which tyramine cannot derepress enzyme synthesis, strongly suggest that a protein factor regulated by catabolite repression is involved in the derepression of arylsulfatase synthesis by tyramine.

Culture Media↗
PubMed1984

Bacillus subtilis glutamine synthetase mutants pleiotropically altered in glucose catabolite repression.

Strain SF22, a glutamine-requiring (Gln-) mutant of Bacillus subtilis SMY, is likely to have a mutation in the structural gene for glutamine synthetase, since this strain synthesized 22 to 55% as much glutamine synthetase antigen as did wild-type cells in a 10-min period but had less than 3% of wild-type glutamine synthetase enzymatic activity. The expression of several genes subject to glucose catabolite repression was altered in the Gln- mutant. The induced levels of alpha-glucosidase, histidase, and aconitase were 3.5- to 4-fold higher in SF22 cells than in wild-type cells grown in glucose-glutamine medium, and citrate synthase levels were 8-fold higher in the Gln- mutant than in wild-type cells. The relief of glucose catabolite repression in the Gln- mutant may result from poor utilization of glucose. Examination of the intracellular metabolite pools of cells grown in glucose-glutamine medium showed that the glucose-6-phosphate pool was 2.5-fold lower, the pyruvate pool was 4-fold lower, and the 2-ketoglutarate pool was 2.5-fold lower in the Gln- cells than they were in wild-type cells. Intracellular levels of glutamine were sixfold higher in the Gln- mutant than in wild-type cells. Measurements of enzymes involved in glutamine transport and utilization showed that the elevated pools of glutamine in the Gln- mutant resulted from a threefold increase in glutamine permease and a fivefold decrease in glutamate synthase. The pleiotropic effect of the gln-22 mutation on the expression of several genes suggests that either the glutamine synthetase protein or its enzymatic product, glutamine, is involved in the regulation of several metabolic pathways in B. subtilis.

Bacillus subtilis↗
PubMed2006

A role for carbon catabolite repression in the metabolism of phosphonoacetate by Agromyces fucosus Vs2.

A strain of Agromyces fucosus, designated Vs2, metabolized a range of organophosphonate compounds as sole phosphorus sources for growth and metabolized phosphonoacetate as a sole carbon, energy and phosphorus source for growth. With phosphonoacetate as the sole phosphorus source and a pyruvate carbon source, transient phosphate release to the medium was observed, in contrast to cultures grown with glucose and phosphonoacetate, where no phosphate release to the medium was observed. Carbon catabolite repression, specifically by means of inducer exclusion of phosphonoacetate, was proposed as the mechanism responsible, and phosphonoacetate hydrolase enzyme assays carried out on cell extracts confirmed that induced phosphonoacetate hydrolase activities were indeed higher in cells grown on pyruvate with phosphonoacetate as sole phosphorus source. This phenomenon has not previously been demonstrated in vivo, and must represent a significant metabolic control of organophosphonate metabolism. The catabolite repression phenomenon was also evident when A. fucosus grew on 2-aminoethylphosphonate as sole phosphorus source, allowing demonstration of a third mode of control for biodegradation of this compound. Excision of stained zymogram gel pieces, followed by tryptic digestion and mass spectrometric analysis, allowed the identification of phosphonoacetate hydrolase-derived peptides.

Actinomycetales↗
PubMed1978

Catabolic N2-acetylornithine 5-aminotransferase of Klebsiella aerogenes: control of synthesis by induction, catabolite repression, and activation by glutamine synthetase.

Klebsiella aerogenes formed two N2-acetylornithine 5-aminotransferases (ACOAT) which were separable by diethylaminoethyl-cellulose chromatography. One ACOAT was repressed when the cells grew on arginine-containing medium, indicating its function in arginine biosynthesis. The second ACOAT was induced when arginine or ornithine was present in the medium as the sole source of carbon or nitrogen, suggesting its function in the catabolism of these compounds. The induced enzyme was purified almost to homogeneity. Its molecular weight is 59,000; it is a pyridoxal 5-phosphate-dependent enzyme and exhibits activity with N2-acetylornithine (Km = 1.1 mM) as well as with ornithine (Km = 5.4 mM). ACOAT did not catalyze the transamination of putrescine or 4-aminobutyrate. The best amino acceptor was 2-ketoglutarate (Km = 0.7 mM). ACOAT formation was subject to catabolite repression exerted by glucose when ammonia was present in excess. When the cells were deprived of nitrogen, ACOAT escaped from catabolite repression. This activation was mediated by glutamine synthetase as shown by the fact that mutants affected in the regulation or synthesis of glutamine synthetase were also affected in the control of ACOAT formation.

Acetamides↗
PubMed1977

Relationship between culture density and catabolite repression of an inducible aliphatic amidase in a thermophilic bacillus.

A direct correlation between the absorbance of a thermophilic bacillus and specific amidase activity was observed, which was found to depend on the cell density of the culture rather than on the time of contact of the culture with the inducer. Dilution of high density cultures caused the specific amidase activity to decrease. Environmental factors such as pH, concentration of inducer or degree of aeration, and level of NH+4 and glutamate had no effect on amidase synthesis. The decrease in amidase activity upon dilution could not be ascribed to destruction by oxygen or by inactivation or decay. Several lines of evidence suggest that catabolite repression is responsible for the phenomenon described. Succinate-grown cultures gave a stronger dilution effect thatn glutamate-grown cells. The mutant strain E-21, relatively resistant to catabolite repression, did not show the characteristic dilution effect nor the direct correlation between absorbance and specific amidase activity.

Acetamides↗
PubMed1970

Cyclic 3',5'-adenosine monophosphate and N-acetylglucosamine-6-phosphate as regulatory signals in catabolite repression of the lac operon in Escherichia coli.

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.

Amidohydrolases↗
PubMed2003

Analysis of the elements of catabolite repression in Clostridium acetobutylicum ATCC 824.

The PTSH gene, encoding the phosphotransferase protein HPr, from Clostridium acetobutylicum ATCC 824 was identified from the genome sequence, cloned and shown to complement a PTSH mutant of Escherichia coli. The deduced protein sequence shares significant homology with HPr proteins from other low-GC gram-positive bacteria, although the highly conserved sequence surrounding the Ser-46 phosphorylation site is not well preserved in the clostridial protein. Nevertheless, the HPr was phosphorylated in an ATP-dependent manner in cell-free extracts of C. Acetobutylicum. Furthermore, purified His-tagged HPr from Bacillus Subtilis was also a substrate for the clostridial HPr kinase/phosphorylase. This phosphorylation reaction is a key step in the mechanism of carbon catabolite repression proposed to operate in B. Subtilis and other low-GC gram-positive bacteria. Putative genes encoding the HPr kinase/phosphorylase and the other element of this model, namely the catabolite control protein CcpA, were identified from the C. Acetobutylicum genome sequence, suggesting that a similar mechanism of carbon catabolite repression may operate in this industrially important organism.

Amino Acid Sequence↗
PubMed2002

HPr kinase/phosphatase of Bacillus subtilis: expression of the gene and effects of mutations on enzyme activity, growth and carbon catabolite repression.

HPr kinase/phosphatase (HPrK/P) is the key protein in regulation of carbon metabolism in Bacillus subtilis and many other Gram-positive bacteria. Whether this enzyme acts as a kinase or phosphatase is determined by the nutrient status of the cell. Mutational analysis of residues in a Walker A box nucleotide-binding motif revealed that it is not only important for kinase but is also involved in phosphatase activity. In addition, a signature sequence specifically conserved among HPrK/P orthologues is required for phosphatase activity and may be involved in interaction with HPr/HPr-(Ser46)-P. Carbon catabolite repression was abolished in a B. subtilis strain expressing a mutant form of HPrK/P deficient in kinase and phosphatase activities. The growth characteristics of this strain were similar to those of the wild-type. In contrast, B. subtilis strains expressing HPrK/P with partial kinase and no phosphatase activities showed growth impairment but exhibited catabolite repression.

Amino Acid Sequence↗
PubMed1985

Isolation and characterization of a cis-acting mutation conferring catabolite repression resistance to alpha-amylase synthesis in Bacillus subtilis.

Bacillus subtilis 168GR10 was shown to contain a mutation, gra-10, which allowed normal temporal activation of alpha-amylase synthesis in the presence of a concentration of glucose that is inhibitory to activation of amylase synthesis in the parent strain, 168. The gra-10 mutation was mapped by phage PBS-1-mediated transduction and by transformation to a site between lin-2 and aroI906, very tightly linked to amyE, the alpha-amylase structural gene. The gra-10 mutation did not pleiotropically affect catabolite repression of sporulation or of the synthesis of extracellular proteases or RNase and was unable to confer glucose-resistance to the synthesis of chloramphenicol acetyltransferase encoded by the cat-86 gene driven by the amyE promoter region (amyR1) inserted into the promoter-probe plasmid pPL603B. It therefore appears that gra-10 defines a cis-regulatory site for catabolite repression, but not for temporal activation, of amyE expression. The evidence shows that temporal activation and glucose-mediated repression of alpha-amylase synthesis in B. subtilis 168 are distinct phenomena that can be separated by mutation.

Bacillus subtilis↗
PubMed2001

Catabolite repression of the citrate fermentation genes in Klebsiella pneumoniae: evidence for involvement of the cyclic AMP receptor protein.

Klebsiella pneumoniae is able to grow anaerobically with citrate as a sole carbon and energy source by a fermentative pathway involving the Na(+)-dependent citrate carrier CitS, citrate lyase, and oxaloacetate decarboxylase. The corresponding genes are organized in the divergent citC and citS operons, whose expression is strictly dependent on the citrate-sensing CitA-CitB two-component system. Evidence is provided here that the citrate fermentation genes are subject to catabolite repression, since anaerobic cultivation with a mixture of citrate and glucose or citrate and gluconate resulted in diauxic growth. Glucose, gluconate, and also glycerol decreased the expression of a chromosomal citS-lacZ fusion by 60 to 75%, whereas a direct inhibition of the citrate fermentation enzymes was not observed. The purified cyclic AMP (cAMP) receptor protein (CRP) of K. pneumoniae bound to two sites in the citC-citS intergenic region, which were centered at position -41.5 upstream of the citC and citS transcriptional start sites. Binding was apparently stimulated by the response regulator CitB. These data indicate that catabolite repression of the citrate fermentation genes is exerted by CRP and that in the absence of repressing carbon sources the cAMP-CRP complex serves to enhance the basal, CitB-dependent transcription level.

Anaerobiosis↗
PubMed2000

Expression of the phospho-beta-glycosidase ArbZ from Lactobacillus delbrueckii subsp. lactis in Lactobacillus helveticus: substrate induction and catabolite repression.

ArbZ from Lactobacillus delbrueckii subsp. lactis was previously shown to enable utilization of the beta-glucoside arbutin by Escherichia coli. The arbZ gene was cloned and expressed in the industrially used beta-glucoside-negative strain Lactobacillus helveticus 3036(62). The transformants were able to ferment not only arbutin, but also cellobiose, salicin and methyl-beta-glucoside (MbetaGlc). Cleavage of beta-glucosides by the transformants depended on the integrity of the cytoplasmic membrane, whereas in cell-free extracts only C(6)-phosphorylated substrates were hydrolysed. This suggested that ArbZ is a phospho-beta-glycosidase. ArbZ activity in transformants of Lb. helveticus was subject to substrate induction mediated by the beta-glucosides arbutin, salicin and MbetaGlc, whereas cellobiose or the beta-galactoside lactose had no inducing effect. Northern blot analysis proved that induction by MbetaGlc was due to enhanced transcription of arbZ. Catabolite repression of arbZ induction was observed with glucose, mannose, fructose and galactose. The induction kinetics observed in the presence of these sugars indicated that at least two different mechanisms are operative in catabolite repression of arbZ in Lb. helveticus.

Arbutin↗
PubMed2001

Induction and catabolite repression mechanisms of cellulase in fungi.

Cellulases are induced in most of fungi only when cellulose or an inducer exists. In Hypocrea jecorina and Penicillium purpurogenum, the respective inducers are sophorose and gentiobiose, which do not have beta-1,4 linkages though cellobiose, which has this linkage, is an inducer in other fungi. beta-Glucosidase, which catalyzes transglucosylation, is the key enzyme in converting cello-oligosaccharides to the inducers for cellulase induction in H. jecorina and P. purpurogenum. There are three states in the regulation of cellulase at the transcriptional level in fungi: expression at a basal level, mass secretion of cellulases induced by inducers, and glucose or catabolite repression. Expression at a basal level allows a small amount of cellulase to hydrolyze cellulose to soluble oligosaccharides or to an inducer if cellulose exists near the mycelia. Once the inducer enters the cell, it triggers full-scale transcription of the cellulase gene mediated by activator proteins and activating elements. After cellulose is degraded a large amount of glucose is liberated, which causes catabolite repression.

Journal Article↗
PubMed2001

Use of catabolite repression mutants for fermentation of sugar mixtures to ethanol.

Use of agricultural biomass, other than corn-starch, to produce fuel ethanol requires a microorganism that can ferment the mixture of sugars derived from hemicellulose. Escherichia coli metabolizes a wide range of substrates and has been engineered to produce ethanol in high yield from sugar mixtures. E. coli metabolizes glucose in preference to other sugars and, as a result, utilization of the pentoses in hemicellulose-derived sugar mixtures is delayed and may be incomplete. Residual sugar lowers the ethanol yield and is problematic for downstream processing of fermentation products. Therefore, a catabolite repression mutant that simultaneously utilizes glucose and pentoses would be useful for fermentation of complex substrate mixtures. We constructed ethanologenic E. coli strains with a glucose phosphotransferase (ptsG) mutation and used the mutants to ferment glucose, arabinose, and xylose, singly and in mixtures, to ethanol. Yields were 87-94% of theoretical for both the wild type and mutants, but the mutants had an altered pattern of mixed sugar utilization. Phosphotransferase mutants metabolized the pentoses simultaneously with glucose, rather than sequentially. Based upon fermentations of sugar mixtures, a catabolite-repression mutant of ethanologenic E. coli is expected to provide more efficient fermentation of hemicellulose hydrolysates by allowing direct utilization of pentoses.

Biomass↗
PubMed2001

Contribution of the phosphoenolpyruvate:mannose phosphotransferase system to carbon catabolite repression in Lactobacillus pentosus.

The role of the Lactobacillus pentosus phosphoenolpyruvate:mannose phosphotransferase system (mannose PTS) in sugar transport and control of sugar utilization was investigated. Growth experiments and measurements of PEP-dependent phosphorylation of sugars, of sugar transport and of catabolic enzyme activity were performed, to compare a wild-type strain with an EIIB(Man) mutant, LPE6, and a ccpA mutant, LPE4. Fructose uptake in wild-type bacteria demonstrated the presence of two fructose-specific PTSs: a high-affinity system, EII(Fru) (K:(m)=52 microM) which is inducible by fructose, and a low-affinity system (K:(m)=300 microM). The latter system was lacking in LPE6 and therefore corresponds to EII(Man). LPE6 was unable to phosphorylate glucose, mannose, N:-acetylglucosamine and 2-deoxyglucose in a PEP-dependent reaction, indicating that these sugars are substrates of EII(Man). Transport and phosphorylation of these compounds was the same in LPE4 and in wild-type bacteria, although growth of LPE4 on these sugars was impaired. In wild-type bacteria and in LPE4 the activity of EII(Fru) was lowered by the presence of EII(Man) substrates in the growth medium, but this decrease was not observed in LPE6. These results indicate that EII(Man) but not CcpA regulates the synthesis of EII(Fru). Mutations in EII(Man) or CcpA resulted in a relief of catabolite repression exerted by EII(Man) substrates on the activity of beta-galactosidase and beta-glucosidase, indicating that EII(Man) and CcpA are important components in catabolite repression in L. pentosus. Fructose-mediated repression of these two enzymes appeared to be correlated with the activity of EII(Fru).

Bacterial Proteins↗
PubMed2005

Catabolite repression of the propionate catabolic genes in Escherichia coli and Salmonella enterica: evidence for involvement of the cyclic AMP receptor protein.

Previous studies with Salmonella enterica serovar Typhimurium LT2 demonstrated that transcriptional activation of the prpBCDE operon requires the function of transcription factor PrpR, sigma-54, and IHF. In this study, we found that transcription from the prpBCDE and prpR promoters was down-regulated by the addition of glucose or glycerol, indicating that these genes may be regulated by the cyclic AMP (cAMP)-cAMP receptor protein (CRP) complex. Targeted mutagenesis of a putative CRP-binding site in the promoter region between prpR and prpBCDE suggested that these genes are under the control of CRP. Furthermore, cells with defects in cya or crp exhibited reduced transcriptional activation of prpR and prpBCDE in Escherichia coli. These results demonstrate that propionate metabolism is subject to catabolite repression by the global transcriptional regulator CRP and that this regulation is effected through control of both the regulator gene prpR and the prpBCDE operon itself. The unique properties of the regulation of these two divergent promoters may have important implications for mechanisms of CRP-dependent catabolite repression acting in conjunction with a member of the sigma-54 family of transcriptional activators.

Escherichia coli↗
PubMed1994

Two different, adjacent and divergent zinc finger binding sites are necessary for CREA-mediated carbon catabolite repression in the proline gene cluster of Aspergillus nidulans.

CREA is the negative regulator mediating carbon catabolism repression in Aspergillus nidulans. We have determined all the sites in the DNA region between the prnD and prnB genes of the proline degradation cluster of this organism which are able to bind a fusion protein containing the zinc finger domain of CREA. The consensus sequence derived for CREA binding is 5'-SYGGRG-3', but not all possible sites derived from this consensus do in fact bind. The binding of at least some sequences of the form 5'-SYGGAG-3' is context dependent. Two different and divergent sites, separated by one base pair (5'-GCGGAGACCCCAG-3'), contain the previously sequenced derepressed mutations and are essential for carbon catabolite repression in vivo. We have studied the binding of CREA to the region by DNase I and methylation protection, and by methylation and depurination interference. We propose that this pair of sites is the physiological, cis-acting element responsible for the carbon catabolite repression of prnB transcription.

Aspergillus nidulans↗
PubMed1994

The mutation DGT1-1 decreases glucose transport and alleviates carbon catabolite repression in Saccharomyces cerevisiae.

Glucose in ethanol-glycerol mixtures inhibits growth of Saccharomyces cerevisiae mutants lacking phosphoglycerate mutase. A suppressor mutation that relieved glucose inhibition was isolated. This mutation, DGT1-1 (decreasing glucose transport), was dominant and produced pleiotropic effects even in an otherwise wild-type background. Growth of the DGT1-1 mutant in glucose was dependent on respiration, and no ethanol was detected in the medium within 7 h of glucose addition. When grown on glucose, the mutant had a reduced glucose uptake and both the low- and high-affinity transport systems were affected. In galactose-grown cells, only the high-affinity glucose transport system was detected. This system had similar kinetic characteristics in the wild type and in the mutant. Catabolite repression of several enzymes was absent in the mutant during growth in glucose but not during growth in galactose. In contrast with the wild type, the mutant grown in glucose had high transcription of the glucose transporter gene SNF3 and no transcription of HXT1 and HXT3. Expression of multicopy plasmids carrying the HXT1, HXT2, or HXT3 gene allowed partial recovery of both fermentative capacity and catabolite repression in the mutant. The results suggest that DGT1 codes for a regulator of the expression of glucose transport genes. They also suggest that glucose flux might determine the levels of molecules implicated as signals in catbolite repression.

Biological Transport↗