Showing papers on "Catabolite repression published in 1988"
TL;DR: A strategy based on plate screening tests was designed for the selection of mutant strains of the fungus Trichoderma reesei suitable for cellulase (EC 3.2.1.4) production on an industrial scale, and the mutant ultimately selected exhibited a four-fold increase in cellulase productivity in cellulose media as compared to the starting strain.
246 citations
TL;DR: Results imply that the operative steps in protease regulation involve de novo synthesis of mRNA, and inhibition of enzyme production by an AMP analogue adenosine 5′-0-thiophosphate implies an involvement for AMP-dependent enzyme systems in derepression.
Abstract: Synthesis of chymoelastase and trypsin by the entomopathogenic fungus Metarhizium anisopliae occurs rapidly (<2 h) during carbon and nitrogen derepression in minimal media. Enzyme levels were enhanced when minimal media were supplemented with insect cuticle or other insoluble polymetic nutrients (e.g. cellulose) that were insufficient to produce catabolite repression. Addition of more readily utilized metabolites (e.g. glucose or alanine) repressed protease production confirming that production is constitutive but repressible. Operational control of protease release involves synthesis rather than secretion because catabolite repression reduced endocellular activity (associated with a sedimentable vacuole containing fraction) as well as extracellular enzyme levels. Studies with metabolic inhibitors indicated that production of Pr1 and Pr2 does not require DNA synthesis. However, synthesis is substantially reduced by inhibitors of transcription (actinomycin D and 8-azoguanine) and translation (cyclohexamide and puromycin). Inhibition by 8-azoguanine is relieved by guanine. These results imply that the operative steps in protease regulation involve de novo synthesis of mRNA. Inhibition of enzyme production by an AMP analogue adenosine 5′-0-thiophosphate implies an involvement for AMP-dependent enzyme systems in derepression. However, neither exogenous cAMP nor an inhibitor of cAMP phosphodiesterase relieved catabolite repression by glucose or NH4Cl. Use of o-vanadate to inhibit plasmalemma ATPase confirmed that secretion of chymoelastase-like protease and trypsin-like protease via the cell membrane is an active process.
80 citations
TL;DR: It was demonstrated that the presence of ORF1 protein in trans was absolutely required for the induction of the hut operon in a hutP1 mutant, and data strongly suggested that OrF1 encodes a positive regulator of the Hut operon.
Abstract: An 8-kilobase HindIII fragment carrying the histidase gene (hutH) and its regulatory region (hutP), from the Bacillus subtilis histidine utilization (hut) operon, was cloned in the temperate bacteriophage phi 105 Histidine utilization was restored in a hutH1 mutant by the specialized transducing phage (phi 105hutH11) The histidase gene in phi 105hutH11 was inducible and was shown to be under catabolite repression The nucleotide sequence of 3,932 base pairs including the hutH and hutP loci revealed three open reading frames (ORFs) The molecular weights of ORF1 and ORF2 proteins were calculated to be 16,576 (151 amino acid residues) and 55,675 (508 amino acid residues), respectively Reverse transcriptase mapping experiments showed that the putative promoter for the hut operon could be recognized by RNA polymerase sigma 43 The transcript starts at an adenosine residue 32 base pairs upstream from the initiation codon of ORF1 hutH+-transforming activity was found in ORF2, indicating that ORF2 encoded the histidase A hutP1 mutation was determined as a substitution of an amino acid in ORF1 By using a specialized transducing phage containing the wild-type ORF1 gene, it was demonstrated that the presence of ORF1 protein in trans was absolutely required for the induction of the hut operon in a hutP1 mutant These data strongly suggested that ORF1 encodes a positive regulator of the hut operon
71 citations
TL;DR: Under normoxic conditions manganese superoxide dismutase biosynthesis is primarily regulated by the same means as the respiratory chain components; that is, by glucose (catabolite) repression rather than by oxygen metabolites.
Abstract: The importance of respiratory chain activity in the induction of manganese superoxide dismutase biosynthesis was examined in the yeast Saccharomyces cerevisiae by immunological measurement of the level of manganese superoxide dismutase and comparison with copper/zinc superoxide dismutase and two subunits of respiratory chain proteins, cytochrome c1 and core 2, under conditions of growth in which respiratory chain activity was varied. Oxygen consumption by the yeast was also monitored during growth. These comparative studies indicated that under normoxic conditions, glucose repression of the respiratory chain subunits resulted in a parallel repression of the level of manganese superoxide dismutase protein. The increase in the protein levels of manganese superoxide dismutase and core 2 protein under derepressing growth conditions reflected an increase in the level of the mRNA for each protein; thus regulation is, at least in part, at the level of transcription. The following observations support the conclusion that under normoxic conditions manganese superoxide dismutase biosynthesis is primarily regulated by the same means as the respiratory chain components; that is, by glucose (catabolite) repression rather than by oxygen metabolites.
1
When yeast cells were transferred from repressing to derepressing growth conditions in normoxia, manganese superoxide dismutase biosynthesis increased at a rate parallel to that of core 2, and occurred approximately 5 h in advance of increased oxygen consumption by the yeast.
2
When an important site of mitochondrial superoxide radical generation, the cytochrome bc1 complex, was inactivated by deletion of the gene coding for one of its subunits, the level of manganese superoxide dismutase protein was not changed in the mutant compared with the parental strain.
However, regulation of manganese superoxide dismutase can be separated from regulation of the respiratory chain proteins in certain instances. During the transition from the logarithmic growth phase to the stationary phase in non-fermentable carbon sources, the level of manganese superoxide dismutase decreased by approximately 50%, whereas the levels of cytochrome c1 and core 2 remained unchanged. Furthermore, yeast grown in hyperoxia of 70–80% oxygen utilizing either repressing or derepressing carbon sources, contained significantly higher levels of manganese superoxide dismutase and copper/zinc superoxide dismutase compared to yeast grown in normoxia, whereas the levels of respiratory chain proteins were not affected by hyperoxia.
When a mutant of S. cerevisiae lacking manganese superoxide dismutase was grown in hyperoxia of 70–80% oxygen with carbon sources requiring a functional respiratory chain, a dramatic decrease in growth rate was observed compared to the parental cells grown under the same conditions. The growth rate of the mutant in 70–80% oxygen did not differ from the parental cells, however, when 10% glucose was the carbon source. Under normoxic conditions the mutant cells grew as well as the parental cells on three and six-carbon sources. However, growth of the mutant was specifically inhibited on the two-carbon sources, ethanol and acetate. When the manganese-superoxide-dismutase-deficient mutant was transformed with a plasmid containing the gene coding for the manganese superoxide dismutase, the mutant regained the ability to grow on the two-carbon sources, indicating that the absence of manganese superoxide dismutase is directly responsible for the inability of this mutant to grow on two-carbon substrates.
59 citations
TL;DR: The nagE gene that codes for enzyme IIN-acetylglucosamine of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) was sequenced and sequence homologies with enzymes IIglucose, II beta-glucOSide, and IIsucrose indicate that residues His-190, His-213, and His-295 of enzyme IInag are also conserved.
Abstract: In Escherichia coli, N-acetylglucosamine (nag) metabolism is joined to glycolysis via three specific enzymes that are the products of the nag operon. The three genes of the operon, nagA, nagB, and nagE, were found to be carried by a colicin plasmid, pLC5-21, from a genomic library of E. coli [Clarke, L., & Carbon, J. (1976) Cell (Cambridge, Mass.) 9,91-99]. The nagE gene that codes for enzyme IIN-acetylglucosamine of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) was sequenced. The nagE sequence is preceded by a catabolite gene activator protein binding site and ends in a putative rho-independent termination site. The amino acid sequence determined from this DNA sequence shows 44% homology to enzymes IIglucose and IIIglucose of the PTS. Enzyme IIN-acetylglucosamine, which has 648 amino acids and a molecular weight of 68,356, contains a histidine at residue 569 which is homologous to the active site of IIIglc. Sequence homologies with enzymes IIglucose, II beta-glucoside, and IIsucrose indicate that residues His-190, His-213, and His-295 of enzyme IInag are also conserved and that His-190 is probably the second active site histidine. Other sequence homologies among these enzymes II suggest that they contain several sequence transpositions. Preliminary models of the enzymes II are proposed.
57 citations
TL;DR: It has been found, that the induction of glyoxysomal enzymes of C2‐metabolism is repressed by methanol in the ecr1 mutant of Pichia pinus with the affected repression of alcohol oxidase by ethanol.
Abstract: Considered are our own data and those found in literature on the properties of yeast mutants impaired in their ability to utilize methanol as sole carbon and energy source; hypotheses about the role of alcohol oxidase and citrate synthase in biogenesis of peroxisomes are proposed. It has been proved that formaldehyde reductase participates in the control of the formaldehyde level in the cell. Properties of mutants defective in the catabolite repression and inactivation of enzymes of methanol metabolism are described. The existence of several autonomous mechanisms of the catabolite repression of alcohol oxidase has been shown. It has been found, that the induction of glyoxysomal enzymes of C2-metabolism is repressed by methanol in the ecr1 mutant of Pichia pinus with the affected repression of alcohol oxidase by ethanol. Data are presented on the regulatory properties of the recently discovered acidification system of the medium induced by methanol. Such acidification occurs due to symport extrusion of protons and formate anions from the cells.
55 citations
TL;DR: The results have identified an apparent novel promoter for P. aeruginosa, which may reflect the presence of a sigma factor required for pobA induction, and suggests primary regulation by a repressor protein which binds p-hydroxybenzoate.
55 citations
TL;DR: The results suggest that nitrate reductase autogenously regulates its own expression and that this control is exerted at the transcriptional level.
Abstract: In Neurospora crassa, the expression of nit-3, the structural gene which encodes nitrate reductase, is highly regulated and requires both nitrate induction and nitrogen catabolite derepression. The major nitrogen regulatory gene, nit-2, acts in a positive fashion to turn on the expression of nit-3 and other nitrogen-related genes during nitrogen derepression. A second regulatory gene, designated nmr, acts in a negative fashion to repress the expression of nitrate reductase and related enzymes, and nmr mutants are partially insensitive to nitrogen repression. Using cloned genes as specific hybridization probes, we demonstrated that nmr does not affect the transcription of nit-2 but does appear to control nit-3 gene expression. Unlike nmr+ expression, nit-3 expression occurred to some degree even under nitrogen repression conditions in nmr mutant cells. In wild-type cells, nitrate reductase gene expression was dependent upon the presence of nitrate as an inducer. In sharp contrast, nit-3 mRNA expression occurred to a full extent in three different nit-3 mutants, even in the complete absence of any added inducer. Similarly, a nit-1 mutant which was devoid of nitrate reductase activity because it lacked an essential molybdenum cofactor expressed nit-3 without a requirement for induction by nitrate. These results suggest that nitrate reductase autogenously regulates its own expression and that this control is exerted at the transcriptional level.
53 citations
TL;DR: Investigation of the effect of induction and carbon catabolite derepression on the synthesis of multiple forms of endoglucanase I by Trichoderma reesei indicates that sophorose may not be the only compound mediating cellulose induction of the specific endglucanases in T. reeseo.
Abstract: A method consisting of sodium dodecyl sulfate-polyacrylamide gel electrophoresis and subsequent detection of endoglucanases by blotting with a polyclonal antibody against endoglucanase I was used to investigate the effect of induction and carbon catabolite derepression on the synthesis of multiple forms of endoglucanase I by Trichoderma reesei. Five forms appeared upon growth on cellulose, whereas four and only two appeared upon growth on lactose (carbon catabolite derepression) and induction by sophorose in a resting cell system, respectively. All endoglucanases detected resembled endoglucanase I in their specificity, since they exhibited no activity toward xylan or paranitrophenyl-beta-D-lactobioside. A small (25-kilodalton) endoglucanase only appeared during growth on cellulose. None of the multiple forms arose by postsecretional modification. The results indicate that sophorose may not be the only compound mediating cellulose induction of the specific endoglucanases in T. reesei.
49 citations
TL;DR: Regulation of afuE and afuR operon transcription is apparently the mechanism whereby glucose regulates antibiotic biosynthesis.
Abstract: Antibiotic biosynthesis is regulated by glucose in Pseudomonas fluorescens HV37a. Fusions between antibiotic biosynthetic operons (afu operons) and the Escherichia coli lac operon were isolated to evaluate the genetic determinants for the regulation of antibiotic biosynthesis. Four afu transcriptional units were defined, afuE, afuR, afuAB, and afuP. The afuE and afuR transcripts were promoted divergently at one locus and were catabolite induced, by 250-fold and 5-fold, respectively; the afuAB and afuP transcriptional units were not linked to the others and were not catabolite induced. Thus, regulation of afuE and afuR operon transcription is apparently the mechanism whereby glucose regulates antibiotic biosynthesis. Catabolite induction of the afuE and afuR transcriptional unit was dependent on the products of the afuA, afuB, and afuP genes. Expression of the afuE transcriptional unit was altered quantitatively in afuE mutants. Apparently the afuE transcriptional unit is regulated, at least in part, by its own gene products. Under inducing conditions, expression of the afuE, afuR, and afuP transcriptional units increased rapidly during a 6-h period.
43 citations
TL;DR: The high-affinity glucose transport process in Saccharomyces cerevisiae whole cells was regulated by catabolite repression and inactivation and the latter finding suggests that there is some regulatory relationship between the two processes.
Abstract: The high-affinity glucose transport process in Saccharomyces cerevisiae whole cells was regulated by catabolite repression and inactivation. The low-affinity process was constitutive, and its activity was inhibited in proportion to the extent of derepression of the high-affinity process. The latter finding suggests that there is some regulatory relationship between the two processes.
TL;DR: Rhodococcus sp.
Abstract: Rhodococcus sp., Pseudomonas paucimobilis and five other bacterial soil isolates were found to be capable of utilizing the l-enantiomer of the herbicide phosphinothricin (2-amino-4-(methylphosphinyl)-butanoic acid) as a nitrogen source. This deamination yielded the structural analogue, 2-oxo-4-(methylphosphinyl)-butanoic acid as the main catabolite of phosphinothricin. On prolonged incubation, slow decarboxylation of the main catabolite occurred with the formation of the stable degradation product 3-methylphosphinico-propanoic acid.
TL;DR: A glucokinase-deficient mutant of Penicillium chrysogenum AS-P-78 was isolated after germ tube-emitting spores were mutated with nitrosoguanidine and selected for growth on lactose-containing medium in the presence of inhibitory concentrations of D-2-deoxyglucose, suggesting that a common regulatory mechanism is involved in carbon catabolite regulation of both sugar utilization and penicillin biosynthesis.
Abstract: One glucokinase-deficient mutant (glk1) of Penicillium chrysogenum AS-P-78 was isolated after germ tube-emitting spores were mutated with nitrosoguanidine and selected for growth on lactose-containing medium in the presence of inhibitory concentrations of D-2-deoxyglucose (3 mM). Penicillin biosynthesis was greatly reduced (55%) in D-glucose-grown cultures of the parental strain, but this sugar had no repressive effect on the rate of penicillin biosynthesis in the mutant glk1. This mutant was deficient in ATP-dependent glucokinase and showed a greatly reduced uptake of D-glucose. The parental strain P. chrysogenum AS-P-78 showed in vitro ATP-dependent phosphorylating activities of D-glucose, D-2-deoxyglucose, and D-galactose. The glk1 mutant was deficient in the in vitro phosphorylation of D-glucose and D-2-deoxyglucose but retained a normal D-galactose-phosphorylating activity. D-Glucose repressed both beta-galactosidase and isopenicillin-N-synthase but not acyl coenzyme A:6-aminopenicillanic acid acyltransferase in the parental strain. The glucokinase-deficient mutant was simultaneously derepressed in carbon catabolite regulation of beta-galactosidase and isopenicillin-N-synthase, suggesting that a common regulatory mechanism is involved in carbon catabolite regulation of both sugar utilization and penicillin biosynthesis.
TL;DR: Detailed analysis of enzyme activity in the parental and deleted derivatives, subcloned into pUC18 and pUC19, suggested that the apparent glucose repression was an artifact arising as a consequence of interactions with the lac transcriptional unit in the plasmid vector.
Abstract: A pseudorandom genomic library of Bacteroides succinogenes DNA, cloned into pUC8 in Escherichia coli, was screened for beta-glucanase activity on 0.1% lichenan plates. Six high-activity clones, containing identical 5.2-kilobase inserts of B. succinogenes DNA, were obtained. The clones exhibited activity solely on beta-glucan substrates containing beta-(1----3)(1----4) linkages, thus manifesting a specific fibrolytic enzyme previously unrecognized in B. succinogenes. A subclone (pJI10) of the original insert (1.35 kilobases in size) expressed full beta-glucanase activity under control of its own promoter. The expression of beta-glucanase in pJI10 appeared subject to catabolite regulation by glucose. Detailed analysis of enzyme activity in the parental and deleted derivatives, subcloned into pUC18 and pUC19, suggested that the apparent glucose repression was an artifact arising as a consequence of interactions with the lac transcriptional unit in the plasmid vector.
TL;DR: In Kluyveromyces marxianus grown on a glucose-containing synthetic medium four different sugar transporters have been identified, three of which appeared to be sensitive to catabolite inactivation.
TL;DR: In 248 strains representing 205 yeast species, changes in pH coupled to glucose addition were followed in unbuffered cell suspensions, indicating a H+-glucose symport was observed and acidification was observed, probably related to the creation of a proton-gradient across the plasma membrane and is generally distributed among yeasts.
Abstract: In 248 strains representing 205 yeast species, changes in pH coupled to glucose addition were followed in unbuffered cell suspensions. Alkalinization of the external medium elicited by glucose, indicating a H+-glucose symport was observed in 34% of the strains, most of them belonging to the genera Rhodotorula, Hansenula and Candida. H+ uptake coupled to glucose transport was observed only after exhaustion of glucose in growth media. This observation was taken as an indication that, in general, the synthesis of H+-glucose symport is under the control of catabolite repression. Subsequently to the addition of glucose, in most yeasts (82%) acidification was observed. This ability is probably related to the creation of a proton-gradient across the plasma membrane and is generally distributed among yeasts.
TL;DR: The microbial production of α‐amylase from Bacillus amyloliquefaciens was investigated and the maltose uptake rate was observed to be the rate‐limiting step compared to the conversion rate of maltose to glucose by intracellular α‐glucosidase.
Abstract: The microbial production of alpha-amylase from Bacillus amyloliquefaciens was investigated. The microorganism was grown using media containing glucose or maltose at 37 degrees C and under aerobic conditions in a 16-L fermentor. The alpha-amylase synthesis from maltose was not found to be inducible but was found to be subject to catabolite repression. The maltose uptake rate was observed to be the rate-limiting step compared to the conversion rate of maltose to glucose by intracellular alpha-glucosidase. The alpha-amylase activity achieved with maltose as a substrate was higher than that achieved with glucose. A slower growth rate and a higher cell density were obtained with maltose. The enzyme production pattern depended upon the nutrient composition of the medium.
TL;DR: A regulatory element has been identified in the promoter region of the gene encoding the 11 kDa subunit VIII of the ubiquinol-cytochrome c oxidoreductase in Saccharomyces cerevisiae that is essential for induction of gene expression during growth in the presence of non-fermentable carbon sources.
Abstract: A regulatory element has been identified in the promoter region of the gene encoding the 11 kDa subunit VIII of the ubiquinol-cytochrome c oxidoreductase in Saccharomyces cerevisiae. The element, which is approximately 40 bp long and situated 185 bp upstream of the initiator ATG, is essential for induction of gene expression during growth in the presence of non-fermentable carbon sources. This is shown by the regulated synthesis of beta-galactosidase in yeast cells harbouring a CYC1-lacZ fusion gene, in which the CYC1 UAS's had been replaced by a 43 bp subunit VIII gene promoter fragment. In addition two DNA-binding activities, which may represent either separate factors or different forms of a single factor, have been detected. Both factors are abundant and they bind in a mutually exclusive fashion to a DNA sequence just upstream of the regulatory element. Although it is unlikely that these factors are directly involved in the response of the subunit VIII gene to catabolite repression, the position of their binding sites relative to the UAS and to the 3'-terminus of a gene located only 361 bp upstream suggest that they are important in modulating transcriptional activity of this region.
TL;DR: The concurrent utilization of the available carbon sources by thermophilic fungi might be an adaptive strategy for opportunistic growth in nature under conditions of low nutrient availability and thermal fluctuations in the environment.
Abstract: The utilization of mixtures of glucose and sucrose at nonlimiting concentrations was studied in batch cultures of two common thermophilic fungi, Thermomyces lanuginosus and Penicilium duponti. The sucrose-utilizing enzymes (sucrose permease and invertase) in both fungi were inducible. Both sugars were used concurrently, regardless of their relative proportion in the mixture. At the optimal growth temperature (50 degrees C), T. lanuginosus utilized sucrose earlier than it did glucose, but at a suboptimal growth temperature (30 degrees C) the two sugars were utilized at nearly comparable rates. The coutilization of the two sugars was most likely possible because (i) invertase was insensitive to catabolite repression by glucose, (ii) the activity and affinity of the glucose transport system were lowered when sucrose was included in the growth medium, and (iii) the activity of the glucose uptake system was also subject to repression by high concentrations of glucose itself. The concurrent utilization of the available carbon sources by thermophilic fungi might be an adaptive strategy for opportunistic growth in nature under conditions of low nutrient availability and thermal fluctuations in the environment.
TL;DR: Strains transformed with the cloned gene on a multicopy plasmid overproduce FbPase but are still subject to strong catabolite repression, however, is slowed down in such strains.
TL;DR: Experimental data of biomass production, oxygen consumption, substrate utilization and lactase production by Kluyveromyces fragilis in four different media were presented and modeled to include the medium composition dependence to the mass transfer equation.
TL;DR: Both endoglucanase and xylan enzyme activity were induced by CMC, whereas xylan induced only xylanase activity, and the effect of protease on induction of cellulase activity is discussed.
Abstract: The regulation of endoglucanase synthesis inPenicillium funiculosum is investigated using a method based on the viscosity lowering effect on carboxy methyl cellulose (CMC) by endoglucanase Cellobiose (1 mg/L) causes induction, whereas glucose (5 g/L) does not repress the enzyme formation Lactose (5 g/L) has no effect on the synthesis of cellulase Avicel and cellulose powder (CP) are the best inducers of cellulase and xylanase activity Both endoglucanase and xylanase activity were induced by CMC, whereas xylan induced only xylanase activity The effect of protease on induction of cellulase activity is discussed
TL;DR: Heat shock enhances the very high level of transcription of the phosphoglycerate kinase (PGK) gene in fermentative cultures of Saccharomyces cerevisiae, and this response of PGK mRNA levels was not found on gluconeogenic carbon sources, and could be switched on or off subject to availability of fermentable carbon source.
Abstract: Summary
Heat shock enhances the very high level of transcription of the phosphoglycerate kinase (PGK) gene in fermentative cultures of Saccharomyces cerevisiae. This response of PGK mRNA levels was not found on gluconeogenic carbon sources, and could be switched on or off subject to availability of fermentable carbon source. The addition of glucose to yeast growing on glycerol resulted in acquisition, within 30–60 min, of the ability to elevate PGK mRNA levels after heat shock. In addition, in aerobic cultures growing on glucose the exhaustion of the medium glucose coincided with a loss of the heat-shock effect on PGK mRNA and a switch-over to slower growth by aerobic respiration. Levels of hsp26 mRNA were analysed during these experiments.
Contrasting with this requirement for fermentable catabolite for manifestation of a heat-shock response of PGK mRNA levels, the PGK enzyme was not synthesized at a greater level in heat-shocked fermentative than in gluconeogenic cultures. PGK is one of only a few proteins made efficiently after mild heat shock of yeast. Thus, heat-stress-induced elevation of PGK mRNA levels does not appreciably increase PGK synthesis during exposure to high temperatures and so its role may be to assist cells repressed in mitochondrial function during recovery following a heat shock.
TL;DR: Optimal fed‐batch culture based on sequential parameter estimation was performed successfully using off‐line analysis while the fermentation was in progress and enzyme production using starch showed similar trends to those obtained using maltose.
Abstract: Fed-batch cultures were performed to maximize the alpha-amylase activity in a bioreactor. Kinetic equations containing a catabolite repression effect were used to model the enzyme formation from Bacillus amyloliquefaciens. Fed-batch culture experiments were performed using maltose to implement the optimal feeding strategy. Optimal fed-batch culture based on sequential parameter estimation was performed successfully using off-line analysis while the fermentation was in progress. The enzyme activity from the fed-batch culture employing maltose was higher than that of the batch culture by 60%. Enzyme production using starch showed similar trends to those obtained using maltose.
TL;DR: The addition of glucose to the culture medium severely repressed beta-glucosidase synthesis, which could not be reversed by exogenous cyclic AMP or dibutyryl cyclicAMP.
Abstract: β-Glucosidase activity in Myceliophthora thermophila D-14 (= ATCC 48104) was inducible and was produced in culture filtrate during growth with various inducers, of which PNPG (p-nitrophenyl-β-d-glucoside) was the most efficient. Induction of β-glucosidase also occurred when the organism was grown in medium supplemented with different carbon sources. Carboxymethyl cellulose, cellobiose, and Solka-Floc were found effective for induction of enzyme biosynthesis. The addition of glucose to the culture medium severely repressed β-glucosidase synthesis, which could not be reversed by exogenous cyclic AMP or dibutyryl cyclic AMP.
TL;DR: The growth and production of cellulolytic enzyme of this fungus are highly favored on carboxy methyl cellulose, jute powder, wheat bran and barley husk in comparison with microcrystalline cellulose (MCC) and absorbent cotton.
TL;DR: The enzyme was sensitive to end-product inhibition by cellobiose but was only moderately inhibited by glucose, and the formation of the enzyme in E. coli was partially dependent on cyclic AMP.
Abstract: Several enzymatic properties of an endoglucanase produced in Escherichia coli by a gene from Pseudomonas fluorescens subsp. cellulosa were investigated. Gel filtration revealed a single peak of M(r) 36,000 with endoglucanase activity. The pH optimum of the enzyme was 7.0. Carboxymethyl cellulose and barley beta-glucan (mixed beta-1,3 and 1,4 linkages) were good substrates, but not laminarin (beta-1,3 linkages), amylose, filter paper, microcrystalline cellulose (Avicel), or cellotriose. The mode of action was typical of an "endo"-acting enzyme. Taken together, these properties do not correspond to those of any of the endoglucanases described in P. fluorescens subsp. cellulosa. Consequently, the gene was designated egIX. The enzyme was sensitive to end-product inhibition by cellobiose but was only moderately inhibited by glucose. The enzyme was formed constitutively in E. coli throughout the growth phase. Urea had no effect on endoglucanase synthesis, but glucose acted as a catabolite repressor. The formation of the enzyme in E. coli was partially dependent on cyclic AMP.
TL;DR: Addition of the substrate methanol remarkably improves constitutive synthesis by preventing catabolite inactivation and delaying degradation of enzymes, indicating that H. polymorpha is constrained to repress synthesis of enzymes involved in the C1-metabolism when ethanol is present as a substrate.
Abstract: A selection by glucosamine for mutants of Hansenula polymorpha insensitive to glucose repression of methanol assimilation is described. Constitutive synthesis of enzymes is established in standard batch cultures of glucosegrown cells. Upon prolonged glucose metabolism the phenotype is masked by catabolite inactivation and degradation of enzymes. Addition of the substrate methanol remarkably improves constitutive synthesis by preventing catabolite inactivation and delaying degradation. Regular peroxisomes of reduced number are formed in mutant cells under repressed conditions. No constitutive synthesis is detectable using ethanol as a carbon source. In addition, this alcohol is detrimental to growth of the mutants, indicating that H. polymorpha is constrained to repress synthesis of enzymes involved in the C1-metabolism when ethanol is present as a substrate.
TL;DR: A. niger gene encoding an aldehyde dehydrogenase enzyme has been cloned and shows expression which is regulated by induction and repression, which differs from that seen for the A. nidulans aldA gene.
Abstract: In order to study mechanisms of gene regulation inA. niger, and to compare these to similar systems inA. nidulans, a gene encoding an aldehyde dehydrogenase enzyme has been cloned. In wild-type strains ofA. niger the gene shows expression which is regulated by induction and repression. Levels of induction by various compounds and the extent of repression under various growth conditions differs from that seen for theA. nidulans aldA gene. Unlike the A.nidulans aldA gene, theA. niger gene has both carbon catabolite repressible and nonrepressible induction mechanisms. Studies of heterologous expression of theA. niger gene inA. nidulans have shown that its expression is regulated by thealcR gene product ofA. nidulans.
TL;DR: Exogenous cAMP was shown to mimic glucose in its effect on the synthesis of glucoamylase in Aspergillus awamori and was found to be due to twofold reduction in the glu coamylases specific mRNA levels.
Abstract: Exogenous cAMP was shown to mimic glucose in its effect on the synthesis of glucoamylase in Aspergillus awamori. cAMP (4 mM) when added to the starch medium blocked the derepression of glucoamylase by inhibiting its protein synthesis by about twofold. The repressive effect of cAMP on the glucoamylase synthesis was found to be due to twofold reduction in the glucoamylase specific mRNA levels. This cAMP related repression of the glucoamylase mRNA levels was most likely brought about at the level of gene transcription as cAMP had no apparent effect on the processing or stability of glucoamylase mRNA.