scholarly journals Regulation of xanthine oxidase in rat liver: modifications of the enzyme activity of rat liver supernatant on storage at 20 degrees

1968 ◽  
Vol 108 (2) ◽  
pp. 349-351 ◽  
Author(s):  
E D Corte ◽  
F Stirpe
Keyword(s):  
Enzyme Activity ◽  
Xanthine Oxidase ◽  
Rat Liver

Activity and stability of rat liver xanthine oxidase in the presence of pyridine

2011 ◽  
Vol 89 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Kaveh Amini ◽  
Mohammad-Hossein Sorouraddin ◽  
Mohammad-Reza Rashidi
Keyword(s):  
Thermal Stability ◽  
Enzyme Activity ◽  
Xanthine Oxidase ◽  
Rat Liver ◽  
Oxidase Activity ◽  
Enzyme Inactivation ◽  
Native Enzyme ◽  
Buffer Solution ◽  
Stability Parameters ◽  
Xanthine Oxidase Activity

In the present study, rat liver xanthine oxidase activity and its thermostability in the presence of pyridine were investigated. The activity of the enzyme was determined by following the formation of uric acid spectrophotometrically. The thermal stability of the enzyme was studied in the presence of 0.0%–2.0% of pyridine in Sorenson’s buffer. Thermal stability parameters (half-life, inactivation constant, and activation energies for enzyme inactivation), thermodynamic constants (ΔH*, ΔS*, and ΔG*) and the kinetic parameters (Km and Vmax), were determined in pyridine-free and pyridine-containing buffer solution. A dramatic reduction was observed in xanthine oxidase activity in the presence of pyridine. However, the pyridine-treated enzyme showed a marked enhancement in thermal stability compared with the native enzyme. The ΔG values for the enzyme activity in the presence of pyridine were found to be about 1.5-fold larger than that calculated for the native enzyme, indicating that the enzyme becomes kinetically more stable in the presence of pyridine. The Km value for xanthine oxidase in the presence of 0.5% pyridine increased by 4.8-fold compared with the enzyme in the pyridine-free buffer solution; however, there was 1.8-fold reduction in the Vmax value in the hydro-organic solution compared with the enzyme activity in the buffer solution. As the stability of enzymes is one of the most difficult problems in protein chemistry, this thermostability property of xanthine oxidase could be of great value in developing novel strategies to improve and expand its application in various areas.

scholarly journals The regulation of rat liver xanthine oxidase. Involvement of thiol groups in the conversion of the enzyme activity from dehydrogenase (type D) into oxidase (type O) and purification of the enzyme

1972 ◽  
Vol 126 (3) ◽  
pp. 739-745 ◽  
Author(s):  
E D Corte ◽  
F. Stirpe
Keyword(s):  
Enzyme Activity ◽  
Xanthine Oxidase ◽  
Rat Liver ◽  
Copper Sulphate ◽  
Liver Homogenate ◽  
Nitrobenzoic Acid ◽  
Complete Inactivation ◽  
Type D ◽  
Pigeon Liver ◽  
Lung And Kidney

1. The ‘xanthine oxidase’ activity of rat liver supernatant, most of which behaves as an NAD+-dependent dehydrogenase (type D) can be rapidly converted into an oxidase (type O) by thiol reagents such as tetraethylthiuram disulphide, copper sulphate, 5,5′-dithiobis-(2-nitrobenzoic acid), N-ethylmaleimide and p-hydroxymercuribenzoate. Treatment with copper sulphate, if prolonged, leads to almost complete inactivation of the enzyme. The effect of these reagents is prevented by dithioerythritol, and in all cases but that of N-ethylmaleimide is reversed by the same thiol. 2. Dithioerythritol prevents and reverses the conversion of xanthine oxidase from type D into type O brought about by storage of rat liver supernatant at -20°C, preincubation under anaerobic conditions, treatment with carbon or with diethyl ether, and reverses, but does not prevent, the conversion obtained by preincubation of the whole liver homogenate. 3. Conversion of the enzyme from type D into type O is effected by preincubation of rat liver supernatant with the sedimentable fraction from rat liver but not from chick or pigeon liver. The xanthine dehydrogenase activity of chick liver supernatant is not changed into an oxidase by preincubation with the sedimentable fraction from rat liver. 4. The enzyme activity of rat liver supernatant is converted from type D into type O during purification of the enzyme: the purified enzyme can be reconverted into type D by dithioerythritol. 5. The enzyme appears as an oxidase in the supernatant of rat heart, intestine, spleen, pancreas, lung and kidney. The enzyme of all organs but intestine can be converted into a dehydrogenase by dithioerythritol.

Effect of saturated fat diets on rat liver NADP-linked enzymes

1965 ◽  
Vol 209 (4) ◽  
pp. 773-780 ◽  
Author(s):  
Helen M. Tepperman ◽  
Jay Tepperman
Keyword(s):  
Fatty Acids ◽  
Enzyme Activity ◽  
Rat Liver ◽  
Corn Oil ◽  
Saturated Fat ◽  
Coconut Oil ◽  
Liver Slices ◽  
Fat Diets ◽  
Effect Of Feeding

The aggregate hexosemonophosphate dehydrogenase (HMPD) activity was found to be higher in livers of rats fed a diet containing saturated fat (hydrogenated coconut oil = H) for 7 days and fasted for 48 hr than it was in similarly prepared animals fed a corn oil (CO) diet. Later, a liver HMPD-increasing effect of feeding H was found in nonfasted animals. Lipogenesis (i.e., the incorporation of acetate-1-C14 into fatty acids by liver slices) was shown to be as low or lower in the H group as in the CO. Liver slices prepared from H and CO diet adapted rats were incubated with either acetate-1-C14 or palmitate-1-C14 and the extent of incorporation of C14 into individual fatty acids was measured. With both substrates more radioactivity was found in 16:1, 18:0, and 18:1 in the case of H-fed animals. It is proposed that a component of the signal for eliciting increased NADP-linked enzyme activity in the H rats was an increased rate of oxidation of NADPH attendant on monoene formation and chain lengthening.

Development of Guanase and Xanthine Oxidase in Rat Liver

1969 ◽  
Vol 132 (1) ◽  
pp. 91-92 ◽  
Author(s):  
E. Silverstein ◽  
O. Zaklynsky ◽  
T. Horn
Keyword(s):  
Xanthine Oxidase ◽  
Rat Liver

scholarly journals Biphasic effect of acute ethanol administration on rat liver tyrosine-2-oxoglutarate aminotransferase activity

1980 ◽  
Vol 186 (3) ◽  
pp. 755-761 ◽  
Author(s):  
A A B Badawy ◽  
B M Snape ◽  
M Evans
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Actinomycin D ◽  
Tyrosine Aminotransferase ◽  
Ethanol Metabolism ◽  
Ethanol Administration ◽  
Aminotransferase Activity ◽  
Biphasic Effect ◽  
Initial Decrease ◽  
Acute Ethanol

1. Acute ethanol administration causes a biphasic change in rat liver tyrosine aminotransferase activity. 2. The initial decrease is significant with a 200 mg/kg dose of ethanol, is prevented by adrenoceptor-blocking agnets and by reserpine, but not by inhibitors of ethanol metabolism, and exhibits many of the characteristics of the inhibition caused by noradrenaline. 3. The subsequent enhancement of the enzyme activity by ethanol is not associated with stabilization of the enzyme, but is sensitive to actinomycin D and cycloheximide. 4. It is suggested that the initial decrease in aminotransferase activity is caused by the release of catecholamines, whereas the subsequent enhancement may be related to the release of glucocorticoids.

scholarly journals Induction of carnitine acetyltransferase by clofibrate in rat liver

1981 ◽  
Vol 194 (1) ◽  
pp. 249-255 ◽  
Author(s):  
B Mittal ◽  
C K R Kurup
Keyword(s):  
Protein Synthesis ◽  
Enzyme Activity ◽  
Rat Liver ◽  
Time Lag ◽  
Mitochondrial Protein ◽  
Carnitine Acetyltransferase ◽  
Enzyme Protein ◽  
General Protein Synthesis ◽  
Liver And Kidney ◽  
General Protein

Administration of the anti-hypercholesterolaemic drug clofibrate to the rat increases the activity of carnitine acetyltransferase (acetyl-CoA-carnitine O-acetyltransferase, EC 2.3.1.7) in liver and kidney. The drug-mediated increase in enzyme activity in hepatic mitochondria shows a time lag during which the activity increases in the microsomal and peroxisomal fractions. The enzyme induced in the particulate fractions is identical with one normally present in mitochondria. The increase in enzyme activity is prevented by inhibitors of RNA and general protein synthesis. Mitochondrial protein-synthetic machinery does not appear to be involved in the process. Immunoprecipitation shows increased concentration of the enzyme protein in hepatic mitochondria isolated from drug-treated animals. In these animals, the rate of synthesis of the enzyme is increased 7-fold.

Mechanisms of conversion of xanthine dehydrogenase to xanthine oxidase in ischemic rat liver and kidney

1988 ◽  
Vol 254 (5) ◽  
pp. G753-G760 ◽  
Author(s):  
T. G. McKelvey ◽  
M. E. Hollwarth ◽  
D. N. Granger ◽  
T. D. Engerson ◽  
U. Landler ◽  
...  
Keyword(s):  
Xanthine Oxidase ◽  
Rat Liver ◽  
Ischemia Reperfusion ◽  
Xanthine Dehydrogenase ◽  
Serum Glutamic Oxaloacetic Transaminase ◽  
Liver Model ◽  
Damage Process ◽  
Liver And Kidney ◽  
Sulfhydryl Modification

Previous studies have proposed and supported a role for the proteolytic, irreversible conversion of xanthine dehydrogenase to xanthine oxidase (XO) in postischemic injury in a wide variety of organs. A second mechanism of conversion, due to sulfhydryl modification and reversible with dithiothreitol (DTT), is potentially important but has not been well investigated. In this study rat liver and kidney were found to produce significant amounts of DTT-reversible XO during normothermic global ischemia. Formation of reversible XO precedes that of irreversible XO by approximately 0.5 h with a strong correlation (r = 0.92) existing between the rate of irreversible XO formation and the concentration of reversible XO. The formation of reversible XO is preceded by a depletion of glutathione with concentrations of glutathione during ischemia correlating (r = 0.85) with the observed concentration of reversible XO. While a large increase in the extent of liver damage occurs concurrently with conversion in an in vivo liver model of liver ischemia, an ischemia-reperfusion regimen (1 h of ischemia plus 0.5 h of reperfusion) that resulted in no conversion caused significant elevations in serum glutamic pyruvic transaminase and serum glutamic-oxaloacetic transaminase. Rats depleted of XO by tungsten dieting release 65% less enzyme after the same insult, suggesting that endogenous XO may also participate in the damage process independent of any conversion.

scholarly journals Properties of cytosolic components activating rat hepatic 5-deiodination in the presence of NADPH

1986 ◽  
Vol 234 (2) ◽  
pp. 391-398 ◽  
Author(s):  
K Sawada ◽  
B C W Hummel ◽  
P G Walfish
Keyword(s):  
Enzyme Activity ◽  
Glutathione Reductase ◽  
Rat Liver ◽  
Column Chromatography ◽  
Reduced Glutathione ◽  
Hydrogen Acceptor ◽  
Simultaneous Addition ◽  
Heat Stable ◽  
Hepatic Microsomes ◽  
Normal Rat

The effects of cytosol, NADPH and reduced glutathione (GSH) on the activity of 5′-deiodinase were studied by using washed hepatic microsomes from normal fed rats. Cytosol alone had little stimulatory effect on the activation of microsomal 5′-deiodinase. NADPH had no stimulatory effect on the microsomal 5′-deiodinase unless cytosol was added. 5′-deiodinase activity was greatly enhanced by the simultaneous addition of NADPH and cytosol (P less than 0.001); this was significantly higher than that with either NADPH or cytosol alone (P less than 0.001). GSH was active in stimulating the enzyme activity in the absence of cytosol, but the activity of 5′-deiodinase with 62 microM-NADPH in the presence of cytosol was significantly higher than that with 250 microM-GSH in the presence of the same concentration of cytosol (P less than 0.001). The properties of the cytosolic components essential for the NADPH-dependent activation of microsomal 5′-deiodinase independent of a glutathione/glutathione reductase system were further assessed using Sephadex G-50 column chromatography to yield three cytosolic fractions (A, B and C), wherein A represents pooled fractions near the void volume, B pooled fractions of intermediate Mr (approx. 13 000), and C of low Mr (approx. 300) containing glutathione. In the presence of NADPH (1 mM), the 5′-deiodination rate by hepatic washed microsomes is greatly increased if both A and B are added and is a function of the concentrations of A, B, washed microsomes and NADPH. A is heat-labile, whereas B is heat-stable and non-dialysable. These observations provide the first evidence of an NADPH-dependent cytosolic reductase system not involving glutathione which stimulates microsomal 5′-deiodinase of normal rat liver. The present data are consistent with a deiodination mechanism involving mediation by a reductase (other than glutathione reductase) in fraction A of an NADPH-dependent reduction of a hydrogen acceptor in fraction B, followed by reduction of oxidized microsomal deiodinase by the reduced acceptor (component in fraction B).

scholarly journals The effects of acetate, metal cations, phenobarbitone, porphyrogens and substrates of glycine acyltransferase on the utilization of haem by rat liver apo-(tryptophan pyrrolase)

1977 ◽  
Vol 164 (2) ◽  
pp. 431-438 ◽  
Author(s):  
A A B Badawy
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Metal Cations ◽  
Oxygenase Activity ◽  
Tryptophan Pyrrolase ◽  
Haem Oxygenase ◽  
Activity Enhancement

1. The utilization of haem by rat liver apo-(tryptophan pyrrolase) under basal conditions and after enhancement of the enzyme activity by various mechanisms was studied under the influence of treatments affecting various aspects of liver haem metabolism. 2. These treatments were: benzoate and p-aminobenzoate as substrates of glycine acyltransferase, acetate as an inhibitor of 5-aminolaevulinate synthase activity, enhancement of 5-aminolaevulinate dehydratase by aluminium, destruction of haem and inhibition of ferrochelatase by porphyrogens, increased haem utilization by phenobarbitone and enhancement of haem oxygenase activity by metal cations. 3. The results show that the haem saturation of the apoenzyme is sensitive to all these treatments. 4. The possible usefulness of tryptophan pyrrolase in studying the regulation of liver haem is suggested.

Sign in / Sign up

Export Citation Format

Share Document