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PubMed1971

Purification, properties, and regulation of glutamic dehydrogenase of Bacillus licheniformis.

Cell-free extracts of Bacillus licheniformis and B. cereus were found to contain high specific activities of nicotinamide adenine dinucleotide phosphate (NADP)-dependent-l-glutamate dehydrogenase [EC 1.4.1.4; l-glutamate: NADP oxidoreductase (deaminating)]. Maximum specific activities were found in extracts of cells during the late exponential phase of growth when ammonium ion served as the sole source of nitrogen. Extremely low specific activities were detected throughout the growth cycle when l-glutamate or Casamino Acids served as the source of carbon and nitrogen. The enzyme was purified 55-fold from crude extracts of B. licheniformis, and apparent kinetic constants were determined. Sigmoidal saturation kinetics were not observed, and various adenylates had no effect on the enzyme. Repression of enzyme synthesis during growth on l-glutamate or Casamino Acids was partially overcome by additions of glucose or pyruvate, and this apparent derepression was totally abolished by inhibitors of ribonucleic acid and protein synthesis. Similarly, additions of l-glutamate or Casamino Acids to cells growing on glucose-ammonium ion resulted in strong repression of enzyme synthesis. It is suggested that the enzyme serves an anabolic role in metabolism. Nicotinamide adenine dinucleotide-dependent glutamate dehydrogenase activity was not detected in five species of Bacillus, irrespective of nutritional conditions or of the physiological age of cells.

Amino Acids↗
PubMed1977

Control of the Production of orthophosphate repressible extracellular enzymes in Neurospora crassa.

The abilities of purine- and pyrimidine-requiring mutants to produce six orthophosphate repressible extracellular enzymes, alkaline phosphatase, 5'-nucleotidase, acid phosphatase, two nucleases and ribonuclease N1 were examined by culturing these mutants in low and high phosphate media containing nucleotide or nucleoside. All the purine requiring mutants produced significantly reduced amounts of alkaline phosphatase, 5'-nucleotidase, acid phosphatase, alkaline nuclease and acid nuclease ranging 0.5-4.2, 5.0-17.4, 25.0-100, 20.3-67.5 and 6.2-48.5%, respectively. Production of ribonuclease N1 was found to be rather stimulated (150-564%) in these mutants. Essentially the same results were obtained for pyrimidine requiring mutants. Among those mutants ad-2 and ad-9 showed relatively high enzyme producing activity. Especially the production of ribonuclease N1 in ad-2 and ad-9 ranged to 4.9- and 5.6-fold that in the wild type. Though nuc-1 mutant (A1) has no ability to produce all these six repressible enzymes, double mutants A1ad-2 and A1ad-9 produced a significant amount of ribonuclease N1 in low and high phosphate media and acid phosphatase in low phosphate media.

Acid Phosphatase↗
PubMed1978

Effect of the mouse mutants testicular feminization and sex reversal on hormone-mediated induction and repression of enzymes.

The mouse mutants testicular feminization and sex reversal have been used to investigate hormone-mediated induction and repression of enzymes. Tfm/Y animals were already known to be androgen insensitive, rendering the androgen-inducible enzymes ADH and beta-glucuronidase noninducible because of an inherited deficiency of a cytosol androgen-receptor complex. The animals display female secondary sexual characteristics. Sxr/+,XX animals display male primary and secondary sexual characteristics with small testes. We demonstrate (1) that the Tfm mutation is pleiotropic, preventing repression of an androgen-repressible enzyme (ornithine aminotransferase) as well as induction of androgen-inducible enzymes, (2) that an estrogen-inducible enzyme (histidine decarboxylase) is not affected by the Tfm mutation, and (3) that Sxr/+,XX animals produce enough androgen for malelike activities of androgen-sensitive enzymes. It was also discovered that histidine decarboxylase repressed by androgen in normal animals, rather than being unaffected by it in Tfm/Y animals, is in fact induced. This unexpected phenomenon is discussed and an explanation is suggested for it.

Alcohol Oxidoreductases↗
PubMed1982

Synthesis and degradation of phenylalanine ammonia-lyase of Rhodosporidium toruloides.

The regulation of the enzyme phenylalanine ammonia-lyase (PAL), which is of potential use in oral treatment of phenylketonuria, was investigated. Antiserum against PAL was prepared and was shown to be monospecific for the enzyme by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The native enzyme and two inactive mutant forms of the enzyme were purified to homogeneity by immunoaffinity chromatography, using anti-PAL immunoglobulin G-Sepharose 4B. Both mutant enzymes contained intact prosthetic groups. The formation of PAL catalytic activity after phenylalanine was added to yeast cultures was paralleled by the appearance of enzyme antigen. During induction, uptake of [3H]leucine into the enzyme was higher than uptake into total protein. Our results are consistent with de novo synthesis of an enzyme induced by phenylalanine, rather than activation of a proenzyme. The half-lives of PAL and total protein were similar in both exponential and stationary phase cultures. No metabolite tested affected the rate of enzyme degradation. Glucose repressed enzyme synthesis, whereas ammonia reduced phenylalanine uptake and pool size and so may repress enzyme synthesis through inducer exclusion. The synthesis of enzyme antigen by a mutant unable to metabolize phenylalanine indicated that this amino acid is the physiological inducer of the enzyme.

Ammonia↗
PubMed1980

Catabolite repression of enzyme synthesis does not prevent sporulation.

In the presence of excess glucose, a decrease of guanine nucleotides in Bacillus subtilis initiated sporulation but did not prevent catabolite repression of three enzymes. Therefore, the ultimate mechanism(s) repressing enzyme synthesis differs from that suppressing sporulation.

Acetoin Dehydrogenase↗
PubMed1970

Phytochrome-mediated repression of enzyme synthesis (lipoxygenase): a threshold phenomenon.

Synthesis of the enzyme lipoxygenase in the cotyledons of the mustard seedling (Sinapis alba L.) is controlled by phytochrome (P(fr)) through a threshold mechanism. The repression of enzyme synthesis by P(fr) is a very rapid process after the threshold level is surpassed. Similarly, enzyme synthesis starts instantaneously and with full speed as soon as the P(fr) level decreases below the threshold level. Thus P(fr) rapidly inhibits synthesis of an enzyme and functions through an all-or-none control mechanism of high precision.

Enzyme Repression↗
PubMed1984

Carbon source regulation of nicotinamide adenine dinucleotide (phosphate) glycohydrolase in Neurospora crassa: induction and repression of enzyme synthesis.

Synthesis and release of NAD(P)ase by Neurospora crassa wild type was studied in experiments in which mycelia grown in Vogel minimal medium were transferred to media containing protein as the only carbon source. Several results are presented suggesting that the NAD(P)ase may be induced by the presence of protein in the culture medium. Low concentrations of sucrose or glucose (0.1%), Casamino acids or some amino acids such as methionine, cysteine, phenylalanine and tryptophan strongly repressed the enzyme synthesis. Under induction conditions NAD(P)ase and alkaline protease appeared together in the culture medium. It would appear that NAD(P)ase and alkaline protease are coordinately regulated by a common control mechanism related to carbon catabolism.

Amino Acids↗
PubMed1976

Control of teichoic and teichuronic acid biosynthesis in Bacillus subtilis 168trp. Evidence for repression of enzyme synthesis and inhibition of enzyme activity.

Phosphate starvation induced teichuronic acid synthesis in cells of Bacillus subtilis 168trp-which had previously been grown with excess phosphate. This induction was prevented when protein systhesis was inhibited immediately prior to phosphate starvation and under these conditions cells continued to form teichoic acid. The converse was true when phosphate was added to cells previously grown in a phosphate-limited chemostat. The increase in teichoic acid synthesis normally following phosphate addition was prevented by chloramphenicol or amino acid starvation and cells continued to make teichuronic acid. This suggestion that repression of enzyme synthesis is involved in controlling the type of wall polymer made was supported by the low levels of UDP-glucose dehydrogenase found in cells grown with excess phosphate and of CDP-glycerol pyrophosphorylase in phosphate-limited cells. The greater amounts of teichoic acid made under phosphate limitation and of teichuronic acid with excess phosphate when protein synthesis was also inhibited indicated that modulation of enzyme activity occurs. Glycerol starvation of a glycerol-requiring mutant did not derepress teichuronic acid synthesis, indicating that glycerol-containing imtermediates do not act as repressors.

Bacillus subtilis↗
PubMed1976

Repressible alkaline phosphatase in Aspergillus niger.

ALP from A. niger is a) P1 repressible enzyme; b) stimulated by addition of Zn++ to the growth medium, and c) that EDTA inhibits the enzyme reversibly, which could be restored by addition of Zn++ and perhaps Mg++. This property is in contrast to the enzyme from N. crassa, which is independent of any metal requirement.

Alkaline Phosphatase↗
PubMed1988

Molecular characterization of yeast regulatory gene CAT3 necessary for glucose derepression and nuclear localization of its product.

The yeast regulatory gene CAT3 has an essential function for the depression of several glucose-repressible enzymes. Therefore, cat3 mutants are unable to grow on maltose or on non-fermentable carbon sources. Unlike the point mutants isolated previously, cat3 null allele strains also failed to utilize raffinose or galactose as sole carbon sources. Sequencing of an 1.6-kb HindIII-BglII fragment complementing cat3 mutations revealed an open reading frame of 322 codons, size of which is in good agreement with the 1.3-kb size of mRNA. No significant similarities with previously sequenced genes could be detected. CAT3-lacZ fusions confirmed the proposed reading frame. A CAT3-lacZ fusion encoding 307 amino acids of CAT3 was able to complement the growth defects of cat3 point mutants and null allele strains. Assay of beta-galactosidase activity under different growth conditions indicated a constitutive expression of the CAT3 gene product. Cellular fractionation studies showed the nuclear localization of the CAT3 protein.

Alleles↗
PubMed1986

Catabolite repressive effects of 5-thio-D-glucose on Saccharomyces cerevisiae.

The effect of the glucose analogue 5-thio-D-glucose (5TG) on the yeast Saccharomyces cerevisiae was studied. Derepression of mitochondrial respiratory chain cytochromes, alcohol dehydrogenase (isoenzyme II), NADH dehydrogenase and maltase was inhibited by 0.5-2 mM-5TG. Growth rate was only slightly affected. Ethanol was efficiently produced with 2 mM-5TG in medium initially containing 0.25% glucose. Mutants resistant to the growth inhibitory effects of 5TG on glycerol medium showed resistance to the catabolite repressing effects of glucose. Other mutants, known to be catabolite repression resistant, showed resistance to 5TG. The analogue seems to inhibit derepression of glucose repressible enzymes with greater potency than glucose itself.

Cytochromes↗
PubMed1987

Inducible thermoalkalophilic polygalacturonate lyase from Thermomonospora fusca.

A thermostable polygalacturonate lyase (PL; EC 4.2.2.2) was secreted by Thermomonospora fusca during stationary phase in pectin-mineral salts medium at 52 degrees C. Biosynthesis was induced by addition of pectic substances to cultures growing on glucose or cellulose but not cellobiose; the disaccharide repressed enzyme synthesis and triggered inactivation of enzyme previously secreted. The PL, purified to electrophoretic and serologic homogeneity, had a molecular size of 56 kilodaltons and an isoelectric point at pH 4.16. The amino acid composition closely resembled that of the major extracellular endoglucanases of the actinomycete. The enzyme had six cystine residues but no detectable sulfhydryl groups. It was inactivated by mild reducing agents and activated by oxygenation, indicating the necessity for disulfide bond maintenance. Temperature and pH optima for the PL reaction were 60 degrees C and 10.45, respectively. Calcium was essential for activity but not stability; calcium dependence curves were altered by low concentrations of toxic metals. The Km for pectin increased 30,000-fold as the percent esterification (methoxylation) of that substrate was increased from 0 to 60%. The size of the minimal susceptible site for PL attack on the pectin molecule was calculated as being equivalent to 10 unesterified residues, based on the correlation of Km values at various degrees of esterification with the percentage of cleavable bonds predicted by a random-number-generating computer program.

Actinomycetales↗
PubMed1986

Fructose induces and glucose represses chloroperoxidase mRNA levels.

The fungus Caldariomyces fumago can be induced to secrete the heme protein chloroperoxidase at levels of 500 mg/liter. Chloroperoxidase synthesis is controlled at the mRNA level. Glucose strongly represses production of chloroperoxidase mRNA and protein, whereas fructose induces both to high levels. Chloroperoxidase has been partially sequenced by automated Edman degradation of tryptic peptides. Based on this amino acid sequence data, a 2-fold degenerate, 29-base oligonucleotide (29-mer) complementary to chloroperoxidase mRNA was synthesized. Polyadenylated RNA, purified from C. fumago, was used as substrate for cDNA synthesis using the 29-mer as primer. cDNAs were made double-stranded and cloned into plasmid pBR322 by conventional methods. Screening the resultant cDNA bank by colony hybridization with the 29-mer as probe showed that 18% of the clones contained the 29-mer sequence. Dideoxy sequencing of one clone (pMA340) identified it as part of the coding region for chloroperoxidase by comparison with known amino acid sequences. In addition, the amino-terminal coding region of clone pMA340 reveals a putative signal peptide for chloroperoxidase. Clone pMA340 was then used in Northern analysis of chloroperoxidase mRNA levels under conditions which induce and repress enzyme secretion.

Amino Acid Sequence↗
PubMed1989

A second global regulator gene (arcB) mediating repression of enzymes in aerobic pathways of Escherichia coli.

In Escherichia coli anaerobic growth lowers the basal or induced levels of numerous enzymes associated with aerobic metabolism. Mutations in arcA (dye) at min 0 relieve this pleiotropic anaerobic repression and render the cell sensitive to the redox dye toluidine blue. In this study we identified a second pleiotropic control gene, arcB, at min 69.5. Mutations, including a deletion, in this gene also relieved the anaerobic repression and caused sensitivity to toluidine blue. Mutations in arcA or arcB did not significantly change the catabolite repression of the target phi(sdh-lacZ) operon, in which lacZ is fused to a structural gene for succinate dehydrogenase, nor did the mutations strikingly influence the pattern of excretion products during glucose fermentation. The presence of arcA+ in a multicopy plasmid restored anaerobic repression in arcB mutants, as indicated by the expression of phi(sdh-lacZ). The arcB product might be a sensor protein for the redox or energy state of the arc regulatory system.

Aerobiosis↗
PubMed1980

[Localization of secreted enzyme-induced repression of its synthesis by the cells].

It was shown that under conditions of regulation of secreted enzyme synthesis by its concentration in microorganisms, the repression of synthesis of the enzyme protein polypeptide chain and the concomitant partial repression of labelled amino acid transport into the cells occur. The regulatory effect can be exerted in the absence of transcription as well. These effects are not realized at the post-transcription or post-translation levels.

Amino Acids↗
PubMed1976

Sugar transport. The crr mutation: its effect on repression of enzyme synthesis.

The accompanying report describes phosphotransferase system-mediated repression in mutants of Salmonella typhimurium and Escherichia coli defective in Enzyme I and histidine-containing phosphate carrier protein (HPr), the general proteins of the phosphotransferase system (PTS). Such repression prevented the cells from synthesizing the catabolic systems required for utilization of the non-PTS compounds glycerol, maltose, melibiose, mannose 6-phosphate, and alpha-glycerol phosphate. This defect can be overcome by introducing a single mutation, designated crr, into the pts mutants. The pts crr double mutants can be induced to synthesize the non-PTS catabolic systems and can therefore grow on the non-PTS sugars. The crr gene is closely linked to but not part of the pts operon, and may be a regulatory gene for the operon. Assay of the PTS proteins in crr mutants showed that the only component detectably affected was a sugar-specific protein of the PTS, Factor IIIG1c, involved in the phsophorylation of glucose (and methyl alpha-glucoside). In some crr mutants Factor IIIG1c was not detected, whereas in others it was present at reduced levels. Thus the crr gene appears to code for or regulate the synthesis of this protein. In addition to the general crr mutants, several classes of sugar-specific crr mutants were isolated. For example, maltose-, melibiose-, and glycerol-specific crr mutants were isolated, each being inducible for the corresponding catabolic enzyme system but not for the others. Unlike the general crr gene, the sugar-specific crr genes do not map near the pts operon.

Biological Transport, Active↗
PubMed1981

Induction and repression of enzymes involved in exogenous purine compound utilization of Bacillus cereus.

5'-Nucleotidase, adenosine phosphorylase, adenosine deaminase and purine nucleoside phosphorylase, four enzymes involved in the utilization of exogenous compounds in Bacillus cereus, were measured in extracts of this organism grown in different conditions. It was found that adenosine deaminase is inducible by addition of adenine derivatives to the growth medium, and purine, nucleoside phosphorylase by metabolizable purine and pyrimidine ribonucleosides. Adenosine deaminase is repressed by inosine, while both enzymes are repressed by glucose. Evidence is presented that during growth of B. cereus in the presence of AMP, the concerted action of 5'-nucleotidase and adenosine phosphorylase, two constitutive enzymes, leads to formation of adenine, and thereby to induction of adenosine deaminase. The ionsine formed would then cause induction of the purine nucleoside phosphorylase and repression of the deaminase. Taken together with our previous findings showing that purine nucleoside phosphorylase of B. cereus acts as a translocase of the ribose moiety of inosine inside the cell (Mura, U., Sgarrella, F. and Ipata, P.L. (1978) J. Biol Chem. 253, 7905-7909), our results provide a clear picture of the molecular events leading to the utilization of the sugar moiety of exogenous AMP, adenosine and inosine as an energy source.

5'-Nucleotidase↗