Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Enzyme Induction”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 937 records · Page 52Linked to original sources
PubMed1988

Oxygen-independent induction of enzyme activities related to oxygen metabolism in yeast by copper.

Aerobic growth of Saccharomyces cerevisiae in the presence of CuSO4 (between 0.1 and 1 mM) caused a generalized induction of major enzyme activities involved in 'housekeeping' routes of oxygen metabolism (cytochrome oxidase, glutathione peroxidases and catalase) which were comparable to or higher than that observed with Cu,Zn-superoxide dismutase. Fumarase and glutathione transferase, tested as controls for oxygen-unrelated activities, were found to decrease under the same conditions. In the absence of oxygen, copper addition to yeast resulted in significant increases of Cu,Zn-superoxide dismutase and glutathione peroxidases and a slight increase of cytochrome oxidase, with catalase remaining undetectable irrespective of whether or not copper was present. Other metal ions tested (Mn2+, Co2+) were unable to produce such effects. It is concluded that copper has a general inducing effect on enzymes related to metabolism of oxygen and oxygen derivatives, which is mediated neither by formation of O2-. and H2O2 nor by interaction with copper-specific apoproteins. These results point to a general role of copper as regulator of the expression of major enzyme activities involved in biological oxygen activation.

Aerobiosis↗
PubMed1981

Effects of phenobarbital upon triacylglycerol metabolism in the guinea pig.

The association between hepatic microsomal enzyme induction and triacylglycerol metabolism was examined in fasting male guinea pigs injected intraperitoneally with 50 mg phenobarbital x kg-1 for 7 days. Enzyme induction was established by a significant increase in hepatic aminopyrine N-demethylase activity, cytochrome P450 content, and hepatic gamma-glutamyl-transferase activity. Increased activity of gamma-glutamyltransferase was also observed in the blood serum of treated animals. The phenobarbital-treated guinea pigs manifested increased hepatic triacylglycerol content and serum triacylglycerol concentration, accompanied by enhanced ability of cell-free fractions of liver to synthesize glycerolipids in vitro from sn-[14C]glycerol 3-phosphate and fatty acids. Microsomal phosphatidate phosphohydrolase accounted for 97% of the total liver activity of this enzyme, and its specific activity was 50-fold higher than that of the cytosolic enzyme when each was measured under optimal conditions. Activity of the cytosolic phosphohydrolase per liver doubled and that of the microsomal phosphohydrolase increased by 40% in the phenobarbital-treated guinea pigs. The microsomal, but not the cytosolic enzyme, showed a significant correlation with hepatic triacylglycerol content. Significant correlation was observed between the various parameters of hepatic microsomal enzyme induction and hepatic triacylglycerol content, suggesting that enzyme induction may promote triacylglycerol synthesis and consequent hypertriglyceridaemia in the guinea pig.

Aminopyrine N-Demethylase↗
PubMed1990

Effects of nutrients and hormones on transcriptional and post-transcriptional regulation of acetyl-CoA carboxylase in rat liver.

The effects of nutrients and hormones on transcriptional and post-transcriptional regulation of acetyl-CoA carboxylase in rat liver were investigated following a cDNA cloning. After refeeding a carbohydrate/protein diet to fasted rats, the transcriptional rate was increased 2.5-fold in only 1 h. The mRNA concentration reached a maximal level of 9-12-fold increase in 8-16 h, and the enzyme induction increased 10-fold in 48 h. By a carbohydrate diet without protein, the transcriptional rate, mRNA concentration and enzyme induction were similarly increased to the levels in the carbohydrate/protein diet. It appears that protein feeding is not necessary to induce acetyl-CoA carboxylase. Corn oil feeding decreased the transcriptional rate. In diabetic rats, the transcriptional rate, mRNA concentration and enzyme induction were very low in comparison with the normal. After insulin treatment, the transcriptional rate was increased 2-fold (the normal level) in 2 h in diabetic rats. By fructose feeding to diabetic rats, the transcriptional rate and mRNA concentration were increased similarly to the levels reached by insulin treatment, while the enzyme induction was increased by only 60%. Thus, it is suggested that insulin is importantly involved in the transcription and also translation of acetyl-CoA carboxylase. On the other hand, triiodothyronine treatment increased the mRNA and enzyme levels in diabetic and normal rats, and somewhat increased the transcriptional rate only in diabetic rats. Triiodothyronine appears to stabilize the mRNA besides having an insulin-like action in acetyl-CoA carboxylase transcription.

Acetyl-CoA Carboxylase↗
PubMed1978

Turnover of rat liver malic enzyme during induction by protein deprivation.

The half-lives of hepatic malic enzyme and total liver soluble proteins were determined in protein-sufficient and protein-deficient rats after injection of tracer doses of radioactively labeled leucine. The results obtained in these experiments have demonstrated that the increased levels of malic enzyme obtained under conditions of severe protein restriction are due to elevated rates of synthesis of the enzyme protein, with no apparent change in the rate of its degradation.

Animals↗
PubMed1980

Induction of enzymes involved in DNA repair and mutagenesis.

Three phenomena examined here have been claimed to reflect the operation of inducible repair systems. It has been postulated that 'SOS repair' involves the induction by DNA-damaging agents of an error-prone repair system that is capable of affecting the replication of damaged DNA. This system works with bacteriophages and animal viruses, in which it is possible to separate the effects of DNA damage on the viral DNA from that on the host cell. Whether this system also operates in repair of the cell's own DNA is, however, controversial. The system appears to have little effect on survival of bacterial cells and its operation in cellular mutagenesis is still not proven, at least in bacteria with otherwise normal repair capacity. 'Adaptation' is the response of bacteria to low doses of methylating agents. Adapted bacteria are more resistant to the lethal and mutagenic action of alkytlating agents. The process includes the induction of an enzyme that 'removes' O6-alkylated bases from DNA and which, unusually, is consumed during the course of the reaction. The reaction itself is also unknown; it does not depend on a nuclease, glycosylase or demethylase, but could use a transmethylase. There is some evidence that an analogous process occurs in animals. The third process affects the synthesis of high molecular weight DNA in cultured mammalian cells that have been exposed to split doses of DNA-damaging agents. It has been postulated that this system is inducible and error-free, but detailed analysis suggests that the observed effect is an artifact arising from an abnormal distribution of sizes of nascent DNA after the second dose, and as a result of exposure to the first dose. Inducible DNA repair systems may be expected to influence kinetics of the dose--response relationships obtained after exposure of cells to mutagens and carcinogens. The interactions between these effects and those produced by inducible pathways of metabolic activation and detoxification are discussed.

Alkylating Agents↗
PubMed1980

Proposed mechanism for neonatal rat tolerance to normobaric hyperoxia.

Induction of two forms of superoxide dismutase, catalase and glutathione peroxidase, occurs very rapidly in neonatal rat lung tissue upon exposure of these animals to 94 + % normobaric oxygen. No such oxygen-mediated enzyme induction occurs in the lungs of adult rats. The aged-dependent pattern of enzyme induction correlates with the well-established age-dependent tolerance of neonatal rats to hyperoxia. Enzyme induction occurs in the lungs of neonates in only those species known to be resistant to oxygen-provoked lung damage. Compromise of oxygen-mediated enzyme induction predisposed the neonatal rats to pulmonary oxygen toxicity. These data have formed the basis of the proposal that oxygen induction of the superoxide dismutases catalase and glutathione peroxidase provides a vital part of the defense mechanism against oxygen toxicity. A biochemical mechanism of oxygen-provoked pulmonary damage has been elaborated to explain the role of each enzyme in the protection against oxygen and free radical toxicity.

Age Factors↗
PubMed1990

A rapid technique for detection of resistance to chloramphenicol in Streptococcus pneumoniae and comparison with minimum inhibitory concentration and disk-diffusion methods.

Fifty-two strains of Streptococcus pneumoniae were examined for production of chloramphenicol acetyltransferase (CAT) by a rapid technique based upon induction of enzyme activity and chemical assay. This method was compared with one measuring the minimum inhibitory concentration (MIC) by agar dilution and a diffusion test with disks containing 10 micrograms, 30 micrograms and 50 micrograms of chloramphenicol. The MIC for 13 chloramphenicol-resistant strains was 16 mg/L and for 39 sensitive strains less than or equal to 4 mg/L. The chemical assay clearly distinguished resistant from sensitive strains; it was technically simple and provided results within 90 min. The distinction between sensitive and resistant bacteria in the disk diffusion assay was clearer with 10-micrograms than with 30-microgram and 50-micrograms disks. However, the chemical CAT assay, with enzyme induction, is recommended when a rapid result is required.

Bacteriological Techniques↗
PubMed1998

Enzyme characteristics of beta-D-galactosidase- and beta-D-glucuronidase-positive bacteria and their interference in rapid methods for detection of waterborne coliforms and Escherichia coli.

Bacteria which were beta-D-galactosidase and beta-D-glucuronidase positive or expressed only one of these enzymes were isolated from environmental water samples. The enzymatic activity of these bacteria was measured in 25-min assays by using the fluorogenic substrates 4-methylumbelliferyl-beta-D-galactoside and 4-methylumbelliferyl-beta-D-glucuronide. The enzyme activity, enzyme induction, and enzyme temperature characteristics of target and nontarget bacteria in assays aimed at detecting coliform bacteria and Escherichia coli were investigated. The potential interference of false-positive bacteria was evaluated. Several of the beta-D-galactosidase-positive nontarget bacteria but none of the beta-D-glucuronidase-positive nontarget bacteria contained unstable enzyme at 44.5 degrees C. The activity of target bacteria was highly inducible. Nontarget bacteria were induced much less or were not induced by the inducers used. The results revealed large variations in the enzyme levels of different beta-D-galactosidase- and beta-D-glucuronidase-positive bacteria. The induced and noninduced beta-D-glucuronidase activities of Bacillus spp. and Aerococcus viridans were approximately the same as the activities of induced E. coli. Except for some isolates identified as Aeromonas spp., all of the induced and noninduced beta-D-galactosidase-positive, noncoliform isolates exhibited at least 2 log units less mean beta-D-galactosidase activity than induced E. coli. The noncoliform bacteria must be present in correspondingly higher concentrations than those of target bacteria to interfere in the rapid assay for detection of coliform bacteria.

Enterobacteriaceae↗
PubMed1983

Relationship between hepatic blood flow and overall metabolism: the hepatic arterial buffer response.

The impact of hepatic blood flow on overall metabolism is not generally appreciated but is of major consequence for homeostasis. Endocrine glands produce and secrete hormones, but for effective and rapid control of hormonal levels, a rapid turnover is required. The liver is the principal organ of clearance for a wide variety of hormones and other endogenous substances. Altered total hepatic blood flow results in altered hepatic clearance rates. The main intrinsic control of hepatic blood flow is designed to hold total hepatic blood flow steady. The liver cannot control portal venous flow (which is simply the sum of outflows of the extrahepatic splanchnic organs); therefore, to hold total blood flow steady, the hepatic artery adjusts total flow in relation to alterations in portal blood flow. This control is referred to as the hepatic arterial buffer response and it functions to regulate blood flow per se rather than nutrient or oxygen regulation. The hepatic arterial flow does not change in response to altered hepatic metabolic activity as shown by the lack of expected vascular changes with altered oxygen content of blood, altered metabolic activity induced by enzyme induction or enzyme inhibition, and altered oxygen uptake or biliary secretion. The hepatic artery is not subservient to local metabolic needs of the liver but rather is controlled in a manner that subserves the homeostatic needs of the entire body. The mechanism of the arterial buffer response is not yet clear but various hypotheses are discussed.

Animals↗
PubMed1984

Theoretical study of oscillatory and resonance phenomena in an open system with induction of enzyme by substrate.

A simple mathematical model of an open metabolic system is constructed in which the metabolism of a substrate is enhanced by induction of the catalyzing enzyme. It is demonstrated that the steady-state in such a system may be approached by damped oscillations of substrate and enzyme levels. If the input rate of substrate into the system has periodic fluctuations, the phenomenon of resonance is observed. Numerical analysis reveals the non-linear character of the resonance.

Enzyme Induction↗
PubMed1987

[Relation between hormonal induction of enzymes regulating glycolysis and convulsive activity in the brain].

The authors have demonstrated the estradiol induction of the key glycolytic enzymes of the brain (hexokinase, phosphofructokinase and pyruvate kinase) which is "switched off" by injection of actinomycin-D--an inhibitor of protein biosynthesis. Another steroid hormone, progesterone, has an inhibitory action on the above enzymes. Administration of estradiol to rats significantly elevates the amplitude and frequency of contractility induced in them, while the same doses of progesterone decrease them. Thus, there is a definite correlation between the induction of glycolytic enzymes and sensitivity toward contractility on the one hand and the estradiol/progesterone ratio on the other. It is possible that activation of glycolysis may reduce the threshold of epileptic attacks providing an additional energy for epileptic manifestations.

Animals↗
PubMed1988

Genotoxic effects of a sub-acute low-level inhalation exposure to a mixture of carcinogenic chemicals.

A study was conducted using a combined testing protocol (CTP), to determine whether short-term biological end-points, singly or in combination, are sufficiently sensitive to identify damage induced by exposure to ambient levels of industrial chemicals. A small-scale inhalation set-up which is both economical and easy to assemble was designed. Mice were exposed to 4 concentrations of a custom-blend mixture of benzene, chloroprene, epichlorohydrin and xylene in a ratio of 2:2:1:2, respectively. The concentrations for benzene, chloroprene and xylene were 0, 0.1, 1.0 and 10 ppm each. Concentrations for epichlorohydrin were half those for the other components. Groups of 22 males and 22 female mice were exposed to each concentration of the mixture for 3 and 6 weeks. Selected biological end-points including urine mutagenesis, bone marrow cell aberrations and micronuclei, spleen lymphocyte aberrations and liver enzyme induction were monitored. The spleen lymphocyte aberrations and liver enzyme induction were the most sensitive end-points. The lymphocytes showed a significant induction of chromosome aberrations from exposure for 3 weeks to all 3 concentrations of the mixtures. After 6 weeks of exposure, significant induction of aberrations was observed after exposure to low and medium concentrations but not to the high concentration. This lack of response at the high concentration after 6 weeks exposure, appeared to correlate with a significant induction of glutathione S-transferase in the liver. Since this enzyme is known to detoxify 3 of the 4 chemicals in our mixture, it may indicate a detoxification mechanism after enzyme induction. The present study indicates that the CTP is sufficiently sensitive to identify toxicological effects after exposure to ambient levels of a gas mixture.

Administration, Inhalation↗
PubMed1980

Changes in the hepatic levels of messenger ribonucleic acid for malic enzyme during induction by thyroid hormone or diet.

Levels of hepatic messenger ribonucleic acid (mRNA) for malic enzyme [L-malate:NADP oxidoreductase (decarboxylating), EC 1.1.1.40] were quantitated in different dietary and hormonal states of the rat. Polysomal or total cellular poly(A)-containing RNA was translated in the rabbit reticulocyte lysate system, which had been treated to reduce endogenous mRNA activity. The relative level of incorporation of radiolabeled amino acid into malic enzyme was determined by immunoprecipitation with antibody to malic enzyme and formaldehyde-fixed Staphylococcus aureus (Cowens I strain) as an immunoadsorbent. The immunoprecipitated product comigrated with purified malic enzyme on sodium dodecyl sulfate--polyacrylamide gel electrophoresis. No malic enzyme was detected when nonspecific antisera or an excess of unlabeled malic enzyme was added during immunoprecipitation. The level of malic enzyme mRNA was found to markedly increase relative to euthyroid, chow-fed rats when the animal was either fed a high carbohydrate, fat-free diet or made hyperthyroid. Animals receiving both treatments had a further increase in mRNA activity to a level which was approximately 0.2% of the total incorporation of [3H]leucine. Levels of malic enzyme activity and the relative rate of synthesis were found to increase roughly in proportion to mRNA levels in these three states. Thus, the induction of malic enzyme by thyroid hormone or high carbohydrate, fat-free diet is due largely to an increase in the mRNA coding for this enzyme.

Animals↗
PubMed1989

Effects of nutrients and insulin on transcriptional and post-transcriptional regulation of glucose-6-phosphate dehydrogenase synthesis in rat liver.

The transcriptional and post-transcriptional regulation of glucose-6-phosphate dehydrogenase induction of rat liver was investigated using a cDNA cloned in our laboratory. By feeding a carbohydrate/protein diet to fasted rats, the mRNA concentration and enzyme induction of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) reached maximal levels about 10-fold those in the fasted rats at 16 h and 72 h, respectively, whereas the transcriptional rate was increased about 3-fold in 6 h. In the protein fed (without carbohydrate) group, both the mRNA concentration and enzyme induction were increased to about 60% of the levels in the carbohydrate/protein fed group and in the group fed on a carbohydrate diet (without protein) to 30-40%. Further, dietary fat significantly reduced the transcriptional rate, mRNA concentration and enzyme induction to less than half, suggesting that dietary fat primarily reduced transcription. Thus, dietary nutrients appear to be involved in the steps preceding the translation. On the other hand, in diabetic rats, the transcriptional rate was significantly decreased as compared to the normal level and restored by insulin-treatment in 4 h. The mRNA concentration was very low in diabetic rats, and was restored to the normal level by insulin treatment in 8 h, and was half restored by fructose feeding. However, the enzyme induction of glucose-6-phosphate dehydrogenase was scarcely restored by fructose, unless accompanied by insulin treatment. Thus, it is suggested that insulin is involved in translation as well as in transcription. Further, the insulin-dependent increase of glucose-6-phosphate dehydrogenase mRNA was blocked by cycloheximide, suggesting that synthesis of a peptide is required.

Animals↗
PubMed1980

Physiological studies of beta-galactosidase induction in Kluyveromyces lactis.

We examined the kinetics of beta-galactosidase (EC 3.2.1.23) induction in the yeast Kluyveromyces lactis. Enzyme activity began to increase 10 to 15 min, about 1/10 of a cell generation, after the addition of inducer and continued to increase linearly for from 7 to 9 cell generations before reaching a maximum, some 125- to 150-fold above the basal level of uninduced cells. Thereafter, as long as logarithmic growth was maintained, enzyme levels remained high, but enzyme levels dropped to a value only 5- to 10-fold above the basal level if cells entered stationary phase. Enzyme induction required the constant presence of inducer, since removal of inducer caused a reduction in enzyme level. Three nongratuitous inducers of beta-galactosidase activity, lactose, galactose, and lactobionic acid, were identified. Several inducers of the lac operon of Escherichia coli, including methyl-, isopropyl- and phenyl-1-thio-beta-d-galactoside, and thioallolactose did not induce beta-galactosidase in K. lactis even though they entered the cell. The maximum rate of enzyme induction was only achieved with lactose concentrations of greater than 1 to 2 mM. The initial differential rate of beta-galactosidase appearance after induction was reduced in medium containing glucose, indicating transient carbon catabolite repression. However, glucose did not exclude lactose from K. lactis, it did not cause permanent carbon catabolite repression of beta-galactosidase synthesis, and it did not prevent lactose utilization. These three results are in direct contrast to those observed for lactose utilization in E. coli. Furthermore, these results, along with our observation that K. lactis grew slightly faster on lactose than on glucose, indicate that this organism has evolved an efficient system for utilizing lactose.

Ascomycota↗
PubMed1993

Induction of hepatic bilirubin and drug metabolizing enzymes by individual herbs present in the traditional Chinese medicine, yin zhi huang.

Yin Zhi Huang (YZH) is a decoction of four plants which is widely used in Asia to treat neonatal jaundice. This study compares the ability of phenobarbital and the individual herbs comprising YZH, Artemisia, Gardenia, Rheum, and Scutellaria baicalensis, to induce hepatic drug and bilirubin metabolizing enzymes in rats. Herbal decoctions (30 ml/kg/day) or phenobarbital (60 mg/kg/day) were administered for 5 days. Only phenobarbital increased cytochrome P-450 levels whereas Gardenia slightly decreased levels. Artemisia, Rheum and phenobarbital increased bilirubin glucuronyl transferase activity. Glucuronidation of alpha-naphthol was increased by Gardenia and phenobarbital, whereas Artemisia and Rheum were ineffective inducers. Phenobarbital was the most effective inducer of glutathione-S-transferase (GSHT) activity. Phenobarbital and Gardenia both induced delta 5-3-ketosteroid isomerase activity, a marker for the Ya subunit of GSHT responsible for intracellular bilirubin transport in liver. The selective patterns of enzyme induction suggest potential value for using specific plant decoctions to modify drug and bilirubin metabolic pathways.

Animals↗
PubMed1990

Synergistic modulation of ectoCa2(+)-ATPase activity of hepatoma (Li-7A) cells by epidermal growth factor and cyclic AMP.

A mercurial-insensitive ectoATPase, which was more active with CaATP than with MgATP, was induced when human hepatoma (Li-7A) cells were cultured in the presence of epidermal growth factor (EGF) and cholera toxin. Cholera toxin could be replaced by forskolin, 8-Br-cAMP, butyryl-cAMP, and dibutyryl-cAMP. Requirement for EGF was specific, but EGF was ineffective if added more than 24 h after the addition of forskolin or cholera toxin. It was concluded that induction of the ectoCa2(+)-ATPase was a consequence of the synergistic actions of EGF and cyclic AMP. The tyrosine kinase activity of the EGF receptor was essential for the induction of ectoCa2(+)-ATPase, since enzyme induction was abolished by a tyrosine kinase inhibitor, genistein. Cycloheximide and actinomycin D were also inhibitory to enzyme induction, indicating that enhancement of enzyme activity by EGF and cAMP was not due to post-translational modification. The results of this and previous investigations established that the two ectoATPases of Li-7A cells are under different regulation.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1980

Effects of phenobarbital upon triacylglycerol metabolism in the rabbit.

1. The association between hepatic microsomal enzyme induction and triacylglycerol metabolism was examined in fasting male rabbits (2kg body wt.) injected intra-peritoneally with 50 mg of phenobarbital per kg for 10 days. 2. Occurrence of enzyme induction was established by a significant increase in hepatic aminopyrine N-demethylase activity and cytochrome P-450 content, as well as a doubling of microsomal protein per g of liver and a 54% increase in liver weight. Parallel increments in hepatic gamma-glutamyltransferase (EC 2.3.2.2) activity occurred; these were more pronounced in the whole homogenate than in the microsomes, which only accounted for 12.5% of the total enzyme activity in the controls and 17.0% in the animals given phenobarbital. Increased activity of gamma-glutamyltransferase activity was also observed in the blood serum of the test animals. 3. The rabbits given phenobarbital manifested increased hepatic triacylglycerol content and the triacylglycerol concentration of blood serum was also elevated. These changes were accompanied by a significantly enhanced ability of cell-free fractions of liver from the test animals (postmitochondrial supernatant and microsomal fractions) to synthesize glycerolipids in vitro from sn-[14C] glycerol 3-phosphate and fatty acids, when expressed per whole liver. Relative to the protein content of the fraction, glycerolipid synthesis in vitro was significantly decreased in the microsomes, presumably consequent upon the dramatic increase in their total protein content, whereas no change occurred in the postmitochondrial supernatant, possibly due to the protective effect of cytosolic factors present in this fraction and known to enhance glycerolipid synthesis. 4. Microsomal phosphatidate phosphohydrolase accounted for 85% of the total liver activity of this enzyme and its specific activity was 20-fold higher than that of the cytosolic phosphatidate phosphohydrolase (EC 3.1.3.4), when each was measured under optimal conditions. A significant increase in the activity of both enzymes per whole liver occurred in the rabbits given phenobarbital. A closer correlation between hepatic triacylglycerol content and and microsomal phosphatidate phosphohydrolase, as well as the above observation, suggest that this, rather than the cytosolic enzyme, may be rate-limiting for triacylglycerol synthesis in rabbit liver. 5. Significant correlations were observed between the various factors of hepatic microsomal-enzyme induction (aminopyrine N-demethylase and gamma-glutamyltransferase activity as well as cytochrome P-450 content) and hepatic triacylglycerol content, suggesting that that microsomal enzyme induction may promote hepatic triacylglycerol synthesis and consequently hypertriglyceridaemia in the rabbit.

Animals↗