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.     

Glucose transport and catabolite repression in Endomycopsis fibuligera yeasts

The role of systems for glucose transport in the manifestation of carbon catabolite repression of glucoamylase synthesis was studied in the yeast Endomycopsis fibuligera. Experimentas were conducted with its mutant AB-192 defective in the system of transport universal for glucose and 2-deoxy-D-glucose (2-DG). The nature of the mutation was established from the following data: (1) transport of labeled glucose into the mutant cells was twice as low in comparison with the parent culture 20-9; (2) transport of labeled 2-DG was suppressed almost entirely; (3) no competition was found between glucose and 2-DG for penetration into the mutant cells. Glucoamylase synthesis in the mutant AB-192 was not sensitive to catabolite repression by glucose. This was confirmed by the resistance of the AB-192 cells to the inhibition by glucose and their complete resistance to the repression by 2-DG. Moreover, an addition of cAMP did not stimulate glucoamylase synthesis by the mutant culture in the presence of glucose and 2-DG. It can be concluded therefore that the resistance of the yeast to catabolite repression by the glucose is caused by the mutation in the system for carbohydrate transport. The results suggest that the system of glucose transport plays an important role in the manifestation of carbon catabolite repression in the yeast Endomycopsis fibuligera.     

Altered end-product patterns and catabolite repression in Escherichia coli

Dobrogosz, Walter J. (North Carolina State University, Raleigh). Altered end-product patterns and catabolite repression in Escherichia coli. J. Bacteriol. 91:2263-2269. 1966.-End products formed during growth of Escherichia coli ML30 on glucose were examined under various conditions known to promote or prevent catabolite repression of the inducible beta-galactosidase system in this organism. Cultures were grown under these conditions in the presence of C(14)-glucose or C(14)-pyruvate. The products formed were assayed isotopically after separation on columns of silicic acid. Under conditions known to promote catabolite repression, glucose was degraded primarily to acetate and CO(2). When repression was turned off by anaerobic shock, glucose metabolism was characterized by the accumulation of ethyl alcohol in addition to acetate and CO(2). The results presented in this report indicate that oxidative decarboxylation of pyruvate may markedly affect the amount of energy that can be derived from glucose catabolism. In turn, the amount of energy derived from catabolic processes may play a key role in the mechanism of catabolite repression.     

Catabolite repression in Enterococcus faecalis

Metabolism of citrate, pyruvate and sugars by Enterococcus faecalis E-239 and JH2-2 and an isogenic, catabolite derepressed mutant of JH2-2, strain CL4, was investigated. The growth rates of E. faecalis E-239 on citrate and pyruvate were 0.58 and 0.63 h(-1), respectively, indicating that both acids were used as energy sources. Fructose and glucose prevented the metabolism of citrate until all the glucose or fructose had been metabolised. Diauxie growth was not observed but growth on glucose and fructose was much faster than on citrate. In contrast, citrate was co-metabolized with galactose or sucrose and pyruvate with glucose. When glucose was added to cells growing on citrate, glucose metabolism began immediately but inhibition of citrate utilisation did not begin for approximately 1.5 h. Growth rates of E. faecalis JH2-2 and its isogenic, catabolite derepressed mutant, strain CL4, on citrate, were 0.41 and 0.36 h(-1), respectively. The catabolite derepressed mutant was able to co-metabolise citrate and glucose at all concentrations of glucose tested (3-25 mM), while its parent, could only metabolise citrate once all the glucose had been consumed. In strains JH2-2 and E-239, the growth rate on citrate decreased as the glucose concentration increased and, in 25 mM glucose, consumption of citrate was inhibited for several hours after glucose had been consumed. These results indicate that catabolite repression by glucose and fructose occurs in enterococci.     

Catabolite repression of tryptophanase in Escherichia coli

Catabolite repression of tryptophanase was studied in detail under various conditions in several strains of Escherichia coli and was compared with catabolite repression of beta-glactosidase. Induction of tryptophanase and beta-galactosidase in cultures grown with various carbon sources including succinate, glycerol, pyruvate, glucose, gluconate, and arabinose is affected differently by the various carbon sources. The extent of induction does not seem to be related to the growth rate of the culture permitted by the carbon source during the course of the experiment. In cultures grown with glycerol as carbon source, preinduced for beta-galactosidase or tryptophanase and made permeable by ethylenediaminetetraacetic acid (EDTA) treatment, catabolite repression of tryptophanase was not affected markedly by the addition of cAMP (3',5'-cyclic adenosine monophosphate). Catabolite repression by glucose was only partially relieved by the addition of cAMP. In contrast, under the same conditions, cAMP completely relieved catabolite repression of beta-galactosidase by either pyruvate or glucose. Under conditions of limited oxygen, induction of tryptophanase is sensitive to catabolite repression; under the same conditions, beta-galactosidase induction is not sensitive to catabolite repression. Induction of tryptophanase in cells grown with succinate as carbon source is sensitive to catabolite repression by glycerol and pyruvate as well as by glucose. Studies with a glycerol kinaseless mutant indicate that glycerol must be metabolized before it can cause catabolite repression. The EDTA treatment used to make the cells permeable to cAMP was found to affect subsequent growth and induction of either beta-galactosidase or tryptophanase much more adversely in E. coli strain BB than in E. coli strain K-12. Inducation of tryptophanase was reduced by the EDTA treatment significantly more than induction of beta-galactosidase in both strains. Addition of 2.5 x 10(-3)m cAMP appeared partially to reverse the inhibitory effect of the EDTA treatment on enzyme induction but did not restore normal growth.     

Carbon catabolite repression of invertase during batch cultivations of Saccharomyces cerevisiae: the role of glucose, fructose, and mannose

When Saccharomyces cerevisiae are grown on a mixture of glucose and another fermentable sugar such as sucrose, maltose or galactose, the metabolism is diauxic, i.e. glucose is metabolized first, whereas the other sugars are metabolized when glucose is exhausted. This phenomenon is a consequence of glucose repression, or more generally, catabolite repression. Besides glucose, the hexoses fructose and mannose are generally also believed to trigger catabolite repression. In this study, batch fermentations of S. cerevisiae in mixtures of sucrose and either glucose, fructose or mannose were performed. It was found that the utilization of sucrose is inhibited by concentrations of either glucose or fructose higher than 5 g/l, and thus that glucose and fructose are equally capable of exerting catabolite repression. However, sucrose was found to be hydrolyzed to glucose and fructose, even when the mannose concentration was as high as 17 g/l, indicating, that mannose is not a repressing sugar. It is suggested that the capability to trigger catabolite repression is connected to hexokinase PII, which is involved in the in vivo phosphorylation of glucose and fructose. Received: 5 May 1998 / Received revision: 3 August 1998 / Accepted: 8 August 1998     

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.     

Role of cyclic-AMP-dependent protein kinase in catabolite inactivation of the glucose and galactose transporters in Saccharomyces cerevisiae.

The derepressed high-affinity glucose transport system and the induced galactose transport system are catabolite inactivated when cells with these transport systems are incubated with glucose. The role of the cyclic AMP cascade in the catabolite inactivation of these transport systems was shown by using mutants affected in the activity of cyclic-AMP-dependent protein kinase (cAPK). In tpk1(w) mutants with reduced cAPK activity, the sugar transport systems were expressed but were not catabolite inactivated. In bcy1 mutants with unbridled cAPK activity resulting from a defective regulatory subunit, the transport systems were absent or present at low levels.     

Glucose effect in tgl mutant of Escherichia col K12 defective in methyl-alpha-D-glucoside transport.

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.     

The effect of glucose on the differential rates of extracellular protein and α-toxin formation by Staphylococcus aureus (Wood 46)

The differential rates of formation of total extracellular protein and alpha-toxin by Staphylococcus aureus (Wood 46) were determined during aerobic growth, at 37 degrees C, in a complex medium containing 0.0, 0.25 or 1.0% (wt/vol) glucose. Different inocula were employed from 1% (vol/vol) of an overnight culture to 100% where bacterial cells were washed and resuspended in fresh medium without change in density. It was shown that under all conditions examined the differential rates of total extracellular protein formation exhibited a biphasic pattern characteristic of regulation based on 'competition'. This biphasic pattern was maintained even in the presence of a large inoculum and a high glucose concentration, conditions considered to favour the onset of catabolite repression. However, a lowering of the initial rate was observed with increasing glucose suggesting the superimposition of catabolite repression as a modulating effect under extreme conditions. In the case of the specific extracellular protein component, alpha-toxin, its differential rate of formation paralleled total exoprotein in all except the condition most favourable for catabolite accumulation when a deviation consistent with a pronounced catabolite repression of this component was demonstrated which was not pH-dependent.     

Beziehungen zwischen katabolischer Repression und Sporulation bei Bacillus subtilis

Acetoin dehydrogenase can be catabolite repressed by numerous sources of carbon. The following results point out that the catabolite repression of this enzyme and the inhibition of sporulation are mediated by the same mechanism:

1. Mutants, able to synthesize acetoin dehydrogenase in the presence of glucose, sporulate in glucose medium at a higher rate than the standard strain.
2. The catabolite repressing effect of a compound and its ability to inhibit sporulation are in a direct relation to each other.
3. The limitation of inorganic phosphate in the growth medium, which is known to favour sporulation, counteracts the catabolite repressing effect of glucose.

     

Regulation of arginine and proline catabolism in Bacillus licheniformis

The enzymes in the arginine breakdown pathway (arginase, ornithine-delta-transaminase, and Delta'-pyrroline-5-carboxylate dehydrogenase) were found to be present in Bacillus licheniformis cells during exponential growth on glutamate. These enzymes could be coincidentally induced by arginine or ornithine to a very high level and their synthesis could be repressed by the addition of glucose, clearly demonstrating catabolite repression control of the arginine degradative pathway. The strongest catabolite repression control of arginase occurred when cells were grown on glucose and this control decreased when cells were grown on glycerol, acetate, pyruvate, or glutamate. The proline catabolite pathway was present in B. licheniformis during exponential growth on glutamate. The proline oxidation and the Delta'-pyrroline-5-carboxylate dehydrogenase in this breakdown pathway were induced by l-proline to a high level. The Delta'-pyrroline-5-carboxylate dehydrogenase was found to be under catabolite repression control. Arginase could be induced by proline and arginine addition induced proline oxidation, suggesting a common in vivo inducer for these convergent pathways.     

Glucose kinase-dependent catabolite repression in Staphylococcus xylosus.

By transposon Tn917 mutagenesis, 16 mutants of Staphylococcus xylosus were isolated that showed higher levels of beta-galactosidase activity in the presence of glucose than the wild-type strain. The transposons were found to reside in three adjacent locations in the genome of S. xylosus. The nucleotide sequence of the chromosomal fragment affected by the Tn917 insertions yielded an open reading frame encoding a protein with a size of 328 amino acids with a high level of similarity to glucose kinase from Streptomyces coelicolor. Weaker similarity was also found to bacterial fructokinases and xylose repressors of gram-positive bacteria. The gene was designated glkA. Immediately downstream of glkA, two open reading frames were present whose deduced gene products showed no obvious similarity to known proteins. Measurements of catabolic enzyme activities in the mutant strains grown in the presence or absence of sugars established the pleiotropic nature of the mutations. Besides beta-galactosidase activity, which had been used to detect the mutants, six other tested enzymes were partially relieved from repression by glucose. Reduction of fructose-mediated catabolite repression was observed for some of the enzyme activities. Glucose transport and ATP-dependent phosphorylation of HPr, the phosphocarrier of the phosphoenolpyruvate:carbohydrate phosphotransferase system involved in catabolite repression in gram-positive bacteria, were not affected. The cloned glkA gene fully restored catabolite repression in the mutant strains in trans. Loss of GlkA function is thus responsible for the partial relief from catabolite repression. Glucose kinase activity in the mutants reached about 75% of the wild-type level, indicating the presence of another enzyme in S. xylosus. However, the cloned gene complemented an Escherichia coli strain in glucose kinase. Therefore, the glkA gene encodes a glucose kinase that participates in catabolite repression in S. xylosus.     

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.     

A lowered concentration of cAMP receptor protein caused by glucose is an important determinant for catabolite repression in Escherichia coli

A decreased intracellular concentration of cAMP is insufficient to account for catabolite repression in Escherichia coli. We show that glucose lowers the amount of cAMP receptor protein (CRP) in cells. A correlation exists between CRP and β-galactosidase levels in cells growing under various conditions. Exogenous cAMP completely eliminates catabolite repression in CRP-overproducing cells, while it does not fully reverse the effect of glucose on β-galactosidase expression in wild-type cells. When the CRP concentration is reduced by manipulating the crp gene, β-galactosidase expression decreases in proportion to the concentration of CRP. These findings indicate that the lowered concentration of CRP caused by glucose is one of the major factors for catabolite repression. We propose that glucose causes catabolite repression by lowering the intracellular levels of both CRP and cAMP.