scholarly journals Purification from rat liver of an enzyme that catalyses the sulphurylation of phenols

1971 ◽  
Vol 123 (5) ◽  
pp. 901-906 ◽  
Author(s):  
F. A. McEvoy ◽  
J. Carroll
Keyword(s):  
Enzyme Activity ◽  
Methyl Ester ◽  
Rat Liver ◽  
The Other ◽  
Male Rat ◽  
Thiol Compounds ◽  
Km Value ◽  
Rat Livers

1. An enzyme (EC 2.8.2.1) that catalyses the transfer of sulphate from adenosine 3′-phosphate 5′-sulphatophosphate to phenols was purified approx. 2000-fold from male rat livers. 2. The purified preparation did not catalyse the sulphurylation of dehydroepiandrosterone, butan-1-ol, l-tyrosine methyl ester, 1-naphthylamine or serotonin. 3. At pH8.0 and 37°C the Km values of the enzyme for p-nitrophenol and adenosine 3′-phosphate 5′-sulphatophosphate are 51 and 14μm respectively. The Km value for either substrate is independent of the concentration of the other. 4. The sulphurylation of phenol is inhibited by thiol compounds and glutathione at a concentration of 3mm caused an approx. 50% decrease in enzyme activity. 5. The Km of the enzyme for adenosine 3′-phosphate 5′-sulphatophosphate is unaffected by the presence of added glutathione but at a concentration of 5mm-glutathione the Km of the enzyme for its phenolic substrate is decreased.

scholarly journals In Situ Measurement of Glutamate Concentrations in the Periportal, Intermediate, and Pericentral Zones of Rat Liver

1997 ◽  
Vol 45 (9) ◽  
pp. 1217-1229 ◽  
Author(s):  
Willie J.C. Geerts ◽  
Ard Jonker ◽  
Louis Boon ◽  
Alfred J. Meijer ◽  
Rob Charles ◽  
...  
Keyword(s):  
Rat Liver ◽  
Correlation Coefficients ◽  
Distribution Patterns ◽  
Male Rat ◽  
Linear Relationships ◽  
Adult Male Rat ◽  
Colorimetric Visualization ◽  
Rat Livers ◽  
Cryostat Sections

We developed a quantitative histochemical assay for measurement of local glutamate concentrations in cryostat sections of rat liver. Deamination of glutamate by glutamate dehydrogenase (GDH) was coupled to the production of formazan and formazan precipitation was used for colorimetric visualization. The method was tested and validated with gelatin model sections with known glutamate concentrations. Calibration graphs showed linear relationships with high correlation coefficients (>96%) between glutamate concentrations or section thickness and absorbance values. The method was reproducible, with a constant percentage of 60 ± 5% of glutamate being converted in gelatin model sections containing glutamate concentrations of 2 mM and higher. Glutamate concentrations were estimated in periportal, intermediate, and pericentral zones of liver lobules that contain low, intermediate, and high GDH activity, respectively. In fed adult male rat livers, periportal zones contained the highest concentrations of glutamate (∼14 mM) and intermediate and pericentral zones ∼13 and 9 mM, respectively. On starvation, glutamate concentrations increased only in the small rim of pericentral cells that express glutamine synthetae, to ∼15 mM. In livers of fetal and newborn rats, glutamate was homogeneously distributed, with a concentration of ∼5 mM. In suckling rat liver, distribution of glutamate was still homogeneous but the concentration was increased to ∼8 mM. These glutamate distribution patterns were in agreement with those detected immunohistochemically.

scholarly journals The dependence on vitamin E and selenium of drug demethylation in rat liver microsomal fractions

1975 ◽  
Vol 146 (2) ◽  
pp. 339-350 ◽  
Author(s):  
A S M Giasuddin ◽  
C P J Caygill ◽  
A T Diplock ◽  
E H Jeffery
Keyword(s):  
Enzyme Activity ◽  
Vitamin E ◽  
Rat Liver ◽  
Selenium Deficiency ◽  
Wide Range ◽  
Km Value ◽  
Demethylase Activity ◽  
In Vitro Induction ◽  
Substrate Concentrations

1. The effects of vitamin E deficiency, and of vitamin E and selenium deficiency, on rat liver microsomal aminopyrine demethylase activity were investigated. It was found that, over a wide range of substrate concentrations, the enzyme activity in preparations from deficient animals was significantly lower than that in controls. 2. Addition of antioxidants in vitro, either to the homogenization or to the assay media, was without significant effect on the depressed enzyme activity. Castration and alteration in dietary protein concentration were also without effect. The rate of oxidation of NADPH was however, lower in preparations from deficient animals. 3. Lineweaver-Burk plots of the reciprocal of enzyme activity and substrate concentration showed a higher Km value in preparations from vitamin E-deficient animals, irrespective of whether selenium was present; the Vmax. was unaffected. These parameters were unchanged when antioxidants were added in vitro. Induction with phenobarbitone and 3-methylcholanthrene showed large changes in Km value which, for preparations from vitamin E-deficient animals, was higher than that for corresponding controls. 4. Examination of the synergism between NADH and NADPH as donors of reducing equivalents for aminopyrine demethylation showed that vitamin E and selenium were only minimally involved in the phenomenon. However, both the initial rate and the extent of demethylation were significantly lower in vitamin E- and selenium-deficient preparations and both nutrients were required for the restoration of full activity. 5. The significance of these results is discussed in the light of our working hypothesis.

scholarly journals Comparative studies on the 25-hydroxylations of cholecalciferol and 1α-hydroxycholecalciferol in perfused rat liver

1978 ◽  
Vol 170 (3) ◽  
pp. 495-502 ◽  
Author(s):  
Masafumi Fukushima ◽  
Yasuho Nishii ◽  
Michiko Suzuki ◽  
Tatsuo Suda
Keyword(s):  
Vitamin D ◽  
Rat Liver ◽  
Linear Relation ◽  
Comparative Studies ◽  
Similar Rate ◽  
The Other ◽  
Perfused Rat Liver ◽  
Km Value ◽  
Derivatives Of ◽  
25 Hydroxycholecalciferol

The 25-hydroxylations of [3H]cholecalciferol and 1α-hydroxy[3H]cholecalciferol in perfused rat liver were compared. Results showed that about twice as much 1α(OH)D3 (1α-hydroxycholecalciferol) was incorporated into the liver as cholecalciferol. 25-Hydroxy[3H]cholecalciferol and 1α-25-dihydroxy[3H]cholecalciferol were not incorporated significantly. Livers isolated from vitamin D-deficient rats formed the 25-hydroxy derivatives of cholecalciferol and 1α(OH)D3 respectively linearly with time for at least 120min. The rate of 1α,25(OH)2D3 (1α,25-dihydroxycholecalciferol) production increased exactly 10-fold on successive 10-fold increases in the dose of 1α(OH)D3, suggesting that hepatic 25-hydroxylation of 1α(OH)D3 is not under metabolic control. On the other hand, the rate of conversion of cholecalciferol into 25(OH)D3 (25-hydroxycholecalciferol) did not increase linearly with increase in the amount of cholecalciferol in the perfusate. The 25-hydroxylation of cholecalciferol seemed to proceed at a similar rate to that of 1α(OH)D3 at doses of less than 1nmol, but with doses of more than 2.5nmol, the conversion of cholecalciferol into 25(OH)D3 became much less efficient, though the linear relation between the amounts of substrate and product was maintained. A reciprocal plot of data on the 25-hydroxylation of cholecalciferol gave two Km values of about 5.6nm and 1.0μm, whereas that for the 25-hydroxylation of 1α(OH)D3 gave a single Km value of about 2.0μm. These results suggest that there are two modes of 25-hydroxylation of cholecalciferol in the liver, which seem to be closely related to the mechanism of control of 25(OH)D3 production by the liver.

scholarly journals Thiol-dependent changes in the properties of rat liver sulphotransferases

1971 ◽  
Vol 123 (3) ◽  
pp. 427-434 ◽  
Author(s):  
D. J. Barford ◽  
J. G. Jones
Keyword(s):  
Ionic Strength ◽  
Methyl Ester ◽  
Molecular Size ◽  
Degree Of Polymerization ◽  
Prolonged Storage ◽  
Kinetic Properties ◽  
Female Rat ◽  
Km Value ◽  
Low Ionic Strength ◽  
Rat Livers

1. Two enzymes (A and B) which catalyse the sulphation of p-nitrophenol and l-tyrosine methyl ester have been isolated from female rat livers. One of these enzymes (A) also catalyses the sulphation of dehydroepiandrosterone. 2. The Km values for the sulphation of p-nitrophenol and l-tyrosine methyl ester by enzyme B at pH7.5 are 1.5μm and 2.9mm respectively. 3. Enzyme B is oxidized on keeping at 0°C when the Km and Vmax. values for the sulphation of p-nitrophenol are increased approx. 200-fold and fourfold respectively. This oxidized preparation of enzyme B fails to catalyse the sulphation of l-tyrosine methyl ester. 4. When the oxidized form of enzyme B is kept at 0°C and low ionic strength then further forms of p-nitrophenol sulphotransferase are produced having even lower affinities for the sulphate acceptor. 5. The Km value for adenosine 3′-phosphate 5′[35S]-sulphatophosphate is not affected during storage of the enzyme under these conditions. 6. Prolonged storage of enzyme B at low ionic strength leads to a considerable degree of polymerization of p-nitrophenol sulphotransferase and l-tyrosine methyl ester sulphotransferase. 7. The changes in the kinetic properties and molecular size of enzyme B during storage are reversed by dithiothreitol.

scholarly journals A novel aldehyde reductase with activity towards a metabolite of aflatoxin B1 is expressed in rat liver during carcinogenesis and following the administration of an anti-oxidant

1993 ◽  
Vol 292 (1) ◽  
pp. 13-18 ◽  
Author(s):  
D J Judah ◽  
J D Hayes ◽  
J C Yang ◽  
L Y Lian ◽  
G C K Roberts ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Aflatoxin B1 ◽  
British Library ◽  
Aldehyde Reductase ◽  
Ph Values ◽  
Development Of Resistance ◽  
Neoplastic Lesions ◽  
Anti Oxidant ◽  
Rat Livers

In contrast with fractions from control animals, an aldehyde reductase, which catalyses the reduction of aflatoxin B1-dihydrodiol, in the dialdehyde form at physiological pH values, to aflatoxin B1-dialcohol, is expressed in cytosolic fractions prepared from rat livers bearing pre-neoplastic lesions, or following treatment with the anti-oxidant ethoxyquin. This expression parallels the development of resistance to the toxin. Unlike the aflatoxin B1-dihydrodiol, the dialcohol does not undergo binding to protein. This enzyme activity could play a mechanistic role in hepatocarcinogenesis and chemoprotection in the rat. Correlated n.m.r. and m.s. spectra are provided in Supplementary Publication SUP 50171 (3 pages), which has been deposited at the British Library Document Supply Centre, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1993) 289, 9.

scholarly journals Treatment of rats with glucagon or mannoheptulose increases mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase activity and decreases succinyl-CoA content in liver

1989 ◽  
Vol 262 (1) ◽  
pp. 159-164 ◽  
Author(s):  
P A Quant ◽  
P K Tubbs ◽  
M D Brand
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Ketone Bodies ◽  
Liver Mitochondria ◽  
Mitochondrial Activity ◽  
Acetyl Coa ◽  
Total Enzyme Activity ◽  
Liver Homogenates ◽  
Rat Livers ◽  
Total Enzyme

1. The activity of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase (EC 4.1.3.5) in extracts of rapidly frozen rat livers was doubled in animals treated in various ways to increase ketogenic flux. 2. Some 90% of the activity measured was mitochondrial, and changes in mitochondrial activity dominated changes in total enzyme activity. 3. The elevated HMG-CoA synthase activities persisted throughout the isolation of liver mitochondria. 4. Intramitochondrial succinyl-CoA content was lower in whole liver homogenates and in mitochondria isolated from animals treated with glucagon or mannoheptulose. 5. HMG-CoA synthase activity in mitochondria from both ox and rat liver was negatively correlated with intramitochondrial succinyl-CoA levels when these were manipulated artificially. Under these conditions, the differences between mitochondria from control and hormone-treated rats were abolished. 6. These findings show that glucagon can decrease intramitochondrial succinyl-CoA concentration, and that this in turn can regulate mitochondrial HMG-CoA synthase. They support the hypothesis that the formation of ketone bodies from acetyl-CoA may be regulated by the extent of succinylation of mitochondrial HMG-CoA synthase.

scholarly journals THE DISTRIBUTION OF DEOXYRIBONUCLEASE IN NORMAL, CIRRHOTIC AND NEOPLASTIC RAT LIVERS

1959 ◽  
Vol 7 (2) ◽  
pp. 139-143 ◽  
Author(s):  
R. DAOUST ◽  
A. CANTERO
Keyword(s):  
Enzyme Activity ◽  
Bile Duct ◽  
Normal Liver ◽  
Liver Parenchyma ◽  
Cirrhotic Liver ◽  
The Other ◽  
Parenchymal Cells ◽  
Rat Livers ◽  
Film Method ◽  
Dna Film

The distribution of deoxyribonuclease in normal, cirrhotic and neoplastic rat livers was investigated histochemically using the gelatine-DNA film method. The bile duct cells and connective tissue elements which are present in abnormal amounts in cirrhotic liver contain little DNAase activity compared with parenchymal tissue. The distribution pattern of DNAase is relatively uniform in normal liver parenchyma but becomes heterogeneous in the parenchyma of cirrhotic and neoplastic tissues. Groups of parenchymal cells in cirrhotic liver and the hepatoma cells in general appear devoid of DNAase activity. The necrotic areas of tissues, on the other hand, show intense enzyme activity.

scholarly journals Guanine deaminase in rat liver and mouse liver and brain

1972 ◽  
Vol 128 (5) ◽  
pp. 1079-1088 ◽  
Author(s):  
K. S Kumar ◽  
A. Sitaramayya ◽  
P. S. Krishnan
Keyword(s):  
Rat Brain ◽  
Rat Liver ◽  
Inhibitory Activity ◽  
Substrate Concentration ◽  
Mouse Liver ◽  
Deae Cellulose ◽  
The Other ◽  
Guanine Deaminase ◽  
Sigmoidal Kinetics ◽  
Km Value

1. The guanine deaminase in rat liver supernatant preparations was resolved into two fractions, A and B, on DEAE-cellulose columns. The two differed in electrophoretic mobility and in various properties. The most noteworthy distinction between A and B components was that the enzyme A activity showed a sigmoid dependence on substrate concentration whereas the enzyme B showed classical Michaelis–Menten kinetics. The Km value of enzyme A for guanine was 5.3μm and that of enzyme B 20μm. 2. The entire guanine deaminase activity of mouse liver was contained in the 15000g supernatant of iso-osmotic homogenates. 3. A reinvestigation of the behaviour of rat brain 15000g supernatant guanine deaminase isoenzymes revealed that one enzyme had sigmoidal kinetics and the other enzyme showed a hyperbolic response. 4. Of the guanine deaminase in mouse brain iso-osmotic sucrose homogenate 80% was recovered in the 15000g supernatant and the rest from the particles. The supernatant guanine deaminase was resolvable into two fractions on DEAE-cellulose columns. One enzyme showed sigmoidal kinetics whereas the other showed a hyperbolic response to increasing substrate concentration; the Km values for the reaction with guanine were respectively 5 and 66μm. 5. The particulate fractions of mouse liver and brain were devoid of any overt inhibitory activity.

scholarly journals Partial purification and properties of an enzyme from rat liver that catalyses the sulphation of l-tyrosyl derivatives

1970 ◽  
Vol 116 (5) ◽  
pp. 797-803 ◽  
Author(s):  
P. Mattock ◽  
J. G. Jones
Keyword(s):  
Methyl Ester ◽  
Rat Liver ◽  
Potent Inhibitor ◽  
Quantitative Difference ◽  
Partial Purification ◽  
Female Rat ◽  
Mixed Substrate ◽  
Partial Separation ◽  
Purification And Properties ◽  
Rat Livers

1. An enzyme that catalyses the transfer of sulphate from adenosine 3′-phosphate 5′[35S]-sulphatophosphate to l-tyrosine methyl ester and tyramine was purified approx. 70-fold from female rat livers. 2. The partially purified preparation is still contaminated with adenosine 3′-phosphate 5′-sulphatophosphate–phenol sulphotransferase (EC 2.8.2.1), but a partial separation of the two enzymes can be achieved by chromatography on columns of Sephadex G-200 and DEAE-Sephadex. 3. The enzyme responsible for the sulphation of l-tyrosine methyl ester and tyramine is activated by dithiothreitol, 2-mercaptoethanol and GSH, the degree of activation being more marked with preparations previously stored at 0 or -10°C. In contrast, the enzymic sulphation of p-nitrophenol is inhibited by all three thiols. Again, there is a quantitative difference in the degree of inhibition of the two enzymes by o-iodosobenzoate, p-chloromercuribenzoate, N-ethylmaleimide and iodoacetate. 4. Mixed-substrate experiments support the hypothesis that the enzyme responsible for the sulphation of l-tyrosine methyl ester and tyramine is separate from that responsible for the sulphation of p-nitrophenol. However, p-nitrophenol is a potent inhibitor of the sulphation of both tyrosyl derivatives whereas these latter compounds have no effect on the sulphation of p-nitrophenol.

Effect of albumin on taurocholate uptake kinetics in rat liver

1987 ◽  
Vol 72 (1) ◽  
pp. 11-17 ◽  
Author(s):  
Rita Aldini ◽  
Aldo Roda ◽  
Antonio Maria Morselli-Labate ◽  
Patrizia Simoni ◽  
Enrico Roda ◽  
...  
Keyword(s):  
Rat Liver ◽  
Uptake Kinetics ◽  
The Other ◽  
Molar Ratio ◽  
Albumin Concentration ◽  
Single Pass ◽  
Rat Livers ◽  
Kinetics Of ◽  
Isolated Rat

1. Isolated rat livers were perfused in a single pass with increasing doses of taurocholate with and without albumin in the perfusion media. 2. The kinetics of taurocholate uptake were thus evaluated. 3. In all the experiments, taurocholate uptake showed Michaelis-Menten kinetics. Increasing the albumin concentration in the medium resulted in an increase in the Km, without effect on the Vmax. When taurocholate and albumin were kept constant (20:1 molar ratio), the Vmax was significantly lower than in the other experiments. 4. These data suggest that taurocholate uptake shows saturation in the absence of albumin and that albumin reduces taurocholate uptake.

Sign in / Sign up

Export Citation Format

Share Document